Inversion roofing: features, advantages and disadvantages


A modern roof, in addition to protection, can also perform useful functions. The most successful example is the use of a flat surface for practical purposes. Previously, this area was rarely used until a non-standard, but effective way of arrangement appeared - an inversion roof.

The difference between a simple roof and an inversion

These two types of roofs have only one thing in common - they are flat. But in fact, they differ in both the structure of the pie and the functionality.

Inverted roofing allows the use of any external covering

A typical flat roof resembles a pie made of the following layers:

  • floor slab;
  • heat insulating material - expanded clay or mineral wool;
  • roll-up waterproofing or PVC membrane;
  • topcoat made of sprayed or rolled bitumen-based materials (liquid rubber).

Thus, a flat roof consists of one or two soft insulation layers sandwiched between or on top of the hard ones. But this design has certain disadvantages. Hydro and vapor barrier does not always boast of complete tightness, as a result of which moisture seeps into the insulation layer, and in the cold season, expanding, tears it apart, separating it from the base of the slab. If it were not for the top waterproofing material, the moisture would evaporate, but the top layer prevents this process. As a result, smudges appear, the place of which is difficult to determine, and, as a result, a fungus appears. The sun's rays and temperature affect the upper waterproofing layer - it becomes loose, changes its texture and quickly loses its protective qualities.

An inverted roof looks different. The very essence of the inversion lies in the unconventional arrangement of layers in the roofing cake - the insulation is located on top of the waterproofing material, due to which additional protection is obtained. From above, the roofing cake is pressed down with ballast. It plays the role of a stabilizing and decorative element that prevents the entire structure from moving. Such placement of waterproofing increases the life of the roof, protects against leaks, sunlight and sudden temperature fluctuations. Water drainage is ensured thanks to the 2.5–5% slope of the entire surface. In some cases, the vapor barrier can be dispensed with.

A green roof will be a great place to relax

Benefits of inversion roofing

The undoubted advantages of this type of roof are:

  1. Increased wear resistance, so it can be used in areas with aggressive climatic conditions.
  2. Long service life - up to 60 years.
  3. Excellent thermal insulation.
  4. Environmental Safety.
  5. Multivariance.
  6. Acceptable price. The savings are based on a reduction in the amount of materials and the process of laying them.
  7. Ability to withstand significant loads.
  8. Possibility of use for constructed buildings.

Disadvantages of inversion roofing

But it is worth remembering about the disadvantages of an inversion roof:

  1. The complexity of the process of moving materials to the roof.
  2. Impossibility of settling in areas with high rainfall.
  3. Problematic repair. A leak, if any, can be eliminated only by removing part of the weight.
  4. Mandatory availability of a sufficient number of drains.
  5. The need for strict adherence to the instructions, otherwise the cake will cease to be functional.

Roof inversion pie structure

Usually the construction looks like this (from bottom to top):

  • waterproofing;
  • insulation;
  • filter layer (geotextile);
  • drainage (gravel, crushed stone);
  • top covering - wood flooring, tiles, paving stones or green (living) roofing.

    The inversion pie layers are reversed

The waterproofing layer, as a rule, is made of roll materials (Euro-ruberoid), as well as PVC and TPO membranes (liquid rubber). And the insulation should be with zero water absorption, so extruded polystyrene foam with closed pores is well suited for this part of the pie. The filter layer is made of geotextile fabric, as it allows moisture to pass through, but retains large particles (debris, leaves or dust). When arranging a plant surface, there are two similar layers: filtering and drainage. Geotextile prevents deformation of polymer layers in contact with rough materials. Drainage is designed to drain storm or melt water from the surface and protect it from external damage. Its thickness must be at least 30-50 mm. Typically 16–32 mm gravel or sand is used.

The pedestrian roof is finished with paving slabs

Video: laying inverted roof layers

Installation features

The number of layers of the inverted roof cake and the materials for it depend on future loads. There are three main types:

  1. Covering for light loads. The cake is made from a layer of insulation and an external coating (euroruberoid or fine gravel). Suitable for use on the roofs of private houses. The cost of such coverage is low, but at the same time it is quite resistant to external influences.
  2. Coverage for medium loads. It is used when the load exceeds the household level. The insulation must be durable and the outer covering must be reliable. Paving slabs or ceramic tiles can be used, as well as any similar material.
  3. The cake for increased loads is stacked in cases where the roof will be used as a parking lot. In addition to the usual layers, a reinforced concrete slab is laid. Accordingly, more durable insulating materials are used that can withstand significant loads. The drainage layer must be at least 30 mm thick.

Installation of an inverted roof on a concrete base

The process of arranging an inverted roof depends on the base material. In the case of laying the roof on a concrete screed, the sequence of actions is as follows:

  1. The first step is to form a slope of 0.5-5 degrees. This is a necessary part of the process, as it will remove moisture from the roof.

    Slope is required to remove excess moisture

  2. On a concrete slab, overlapping the screed, a sealed waterproofing carpet made of one or two layers of roll material (PVC, polymer, bitumen) is laid. The main requirement for it is durability.

    Overlap waterproofing

  3. Next, a layer of slab insulation (expanded polystyrene) is mounted. It does not fix, as this will impede the flow of water.
  4. Geotextile material is laid on the insulation, which distributes the load and prevents the upper drainage layer from entering the thermal insulation.

    Geotextiles are an important component of inversion roofing

  5. Gravel, crushed stone or other similar surface is used as ballast. It protects the cake from external influences.
  6. Arrangement of the parapet. It prevents the weight from blowing off the roof. The parapet should rise above the roof level.

    The pie at the parapet is practically no different from the traditional inversion

  7. After that, the gutters are mounted. They should be carefully insulated, fitted with filters and located in places accessible for regular cleaning.

    The funnels of the drainage system must be located in accessible places, which is important for their cleaning.

Video: inversion roof waterproofing

Installation of an inverted roof on a wooden base

Compared to a concrete slab, a wooden base has a lower load-bearing capacity, so it can deform over time. To avoid this, the load must be carefully calculated. The roof beam must be treated with antiseptic and moisture-protective agents, and the places where the beams adjoin the walls are insulated with roofing material. For waterproofing a wooden base, it is better to use polymer membranes, since they do not require hot installation. It is also possible to mount the first layer by hand, and the second one can be fused. To minimize the likelihood of fire, DSP boards are recommended for solid sheathing.

An exploitable roof is also suitable for a wooden shed.

The scheme of a pie on a wooden base is as follows:

  • beams;
  • solid crate;
  • waterproofing;
  • filter layer;
  • non-flammable insulation;
  • geotextile;
  • ballast (deck board, soil, decking, rubber mats, tiles).

Green inversion roof

Most often, an inverted roof is chosen for arranging a garden or lawn lawn on the roof. But at the same time, it is worth remembering the basic rules, the observance of which is mandatory:

  1. A living roof, the ballast of which is the soil-vegetation layer, requires drainage from a polymer membrane. It is designed to drain excess moisture or retain it during dry periods.
  2. The fertile layer should consist of a compost-vermiculite, expanded clay or perlite mixture.
  3. Lawn grass, mosses or sedums are used for landscaping.

Video: principles of building the right pie for a green roof

A correctly calculated and correctly laid inversion roof will not only make the house energy-efficient, but also transform its appearance and provide additional usable space. Another plus is that it is quite possible to do it yourself.


If you want to organize a parking lot on the roof, then, first of all, you need to find an experienced and competent contractor who has already carried out such orders.

Builders first install the screed on the concrete surface, then lay a waterproofing layer on top. On top, you need to lay plates for thermal insulation, followed by a filter layer. Sprinkle gravel on top. The last stage is the laying of paving slabs. It turns out that you create not just a roof, but a real courtyard where you can open a cafe, playground, parking, etc. It is worth noting that experts advise against planting trees on the roof. If you want to plant greenery on the site, then it is better to limit yourself to flowers, grass and shrubs. Some building owners leave the roof for guest parking, in such cases the gravel can be replaced with concrete.

Inversion roofing - what is it ... Inversion roofing - what is it ... Inversion roofing - what is it ... Inversion roof - what is it ... Inversion roof - what is it ...

Currently, a large number of companies operate in this market segment, which set different prices for roofing construction. When choosing between candidates, give your preference to more experienced performers.


What is inversion roofing

The overwhelming majority of mansions and cottages in Moscow and the Moscow region have pitched roofs. Flat roofs are rarely used and are most often used to cover protruding parts of a house, terraces, etc. Structurally, a traditional flat roof, often referred to as a "soft" roof, consists of a load-bearing slab on which a heat-insulating material (mineral wool slabs) is laid along a vapor barrier layer, protected from the effects of atmospheric precipitation by a waterproofing carpet based on bitumen-containing roll materials (Fig. 1).

However, this design has a number of disadvantages. It is not always possible to ensure the complete tightness of the vapor barrier layer, as a result of which water vapor penetrates into the thickness of the insulation and accumulates in it, since the dense waterproofing carpet prevents moisture evaporation. Over time, a lot of moisture accumulates in the insulation, which flows down, forming wet spots on the ceiling.In addition, at negative temperatures, water freezes, increases in volume and tears the waterproofing off from the base. During operation, the waterproofing carpet is exposed to climatic and mechanical influences, which leads to cracks, through which water penetrates into the room, leaks are formed, the cause of which can be very difficult to establish and eliminate.

1 - floor slab
2 - fastening the insulation
3 - vapor barrier
4 - insulation
5 - waterproofing carpet
6 - additional insulation

1 - overlap
2 - waterproofing carpet
3 - insulation made of extruded polystyrene foam
4 - filter material
5 - a layer of gravel with a thickness of at least 50 mm

There is an alternative constructive solution for a flat roof - the so-called. inversion roof, practically devoid of these disadvantages. Its difference lies in the fact that the insulating layer is located not under the waterproofing carpet, but above it (Fig. 2). This design protects the waterproofing layer from the damaging effects of ultraviolet rays, sudden temperature changes, freezing and thawing cycles, as well as mechanical damage, which provides an increase in the service life of an inverted roof compared to traditional (so-called "soft") roofing. The design of the inversion roof allows it to be used as an exploited flat roof on which you can sunbathe, put a table and chairs, plant grass or arrange a flower garden.

On the reinforced concrete slab of the covering, along the screed (or without it), a waterproofing carpet is arranged from two layers of "Filisol" or one layer of "Rooflite", on top of which the insulation slabs are laid. A carpet of filter material is laid on the thermal insulation, and then gravel is poured. If the roof is in use, then paving slabs can be laid. The recommended slope of inverted roofs is 2.5-5%.

During the operation of the roof, melt or rain water flows down through the gravel layer, passes through the filter material, partially through the joints between the insulation plates and flows down the waterproofing carpet into the drainage devices.

Insulation for inversion coatings

For insulating an inverted roof, only non-hygroscopic materials are applicable that can maintain high thermal insulation characteristics in a humid environment. These requirements are met by closed-cell extruded foams, which have close to zero water absorption, good heat-shielding characteristics in a humid environment, and sufficient strength.

Insulation protection in inverted roofs

To protect the insulation from floating up, exposure to ultraviolet rays and strong winds, it is loaded with a layer of washed rolled gravel 16-32 mm in size. Sand or gravel mixtures are not used as a loading material. The thickness of the gravel layer is taken depending on the thickness of the insulation slabs.

You can also use paving slabs or cobblestones as a weight. If you arrange a lawn or a small flower garden on the roof of the house, then the soil will play the role of a protective layer. This design is shown in Fig. 3.

The gravel layer is laid on a special filtering material (fiberglass, "Taipar" material, etc.), which allows water to pass through well, but is an obstacle to the passage of solid particles of soil or sand. The filtering material prevents the top (soil) layer of the exploited roof from being washed away and protects the insulation plates from siltation.

1- reinforced concrete floor slab
2 - primer layer
3 - waterproofing carpet from roll materials
4 - extruded polystyrene foam
5 - filter material
6 - drainage layer of gravel
7 - filter material
8 - soil

1 - reinforced concrete floor slab
2 - primer layer
3 - waterproofing carpet from roll materials
4 - extruded polystyrene foam
5 - filter material
6 - drainage layer of gravel
7 - metal apron
8 - cap of the drainage funnel
9 - additional layer of waterproofing

Structural elements of inversion cover

An important structural element is the junction of the drain funnel to the coating. Along the perimeter of the hole, it is necessary to lay an additional layer of waterproofing material, install a metal apron and ensure the slope of the waterproofing carpet towards the drain funnel (Fig. 4).

In order to ensure a reliable abutment of the inverted roof to the outer wall of the house, additional layers of waterproofing material are arranged in the junction zone, which are attached to the outer wall above the level of the covering (Fig. 5).

1 - reinforced concrete floor slab
2 - primer layer
3 - waterproofing carpet from roll materials
4 - extruded polystyrene foam
5 - filter material
6 - drainage layer of gravel with a diameter of 4-8 mm
7 - drainage layer of gravel with a diameter of 16-32 mm
8-paving slabs
9 - soil layer (optional)
10 - outer wall
11 - non-hardening sealant
12 - metal apron
13 - outer wall cladding
14 - additional layer of hydro-insulating material

1 - reinforced concrete floor slab
2 - primer layer
3 - waterproofing carpet from roll materials
4 - extruded polystyrene foam
5 - filter material
6 - a layer of gravel with a thickness of at least 50 mm
7 - drainage bed of fine (4-8 mm) gravel
8 - paving slabs flooring
9 - thermal insulation material

To increase the thermal insulation properties of the coating, as well as to eliminate the likelihood of cracking in places where the waterproofing carpet bends, near the outer wall and parapets on the floor, it is advisable to make a bevel of heat-insulating material (Fig. 6). Protection of the insulating layer from mechanical damage and an increase in the resistance of the gravel layer to the effects of increased wind loads are achieved by laying concrete (sidewalk) tiles around the perimeter of the coating (along the parapet and the outer wall).

As already noted, the bulk of the water that enters the roof during rain or is formed as a result of melting snow flows through the gutters. However, a certain amount of moisture inevitably seeps into the gap between the insulation and the waterproofing carpet, from where it subsequently evaporates outward, passing through the joints of the insulation plates. Therefore, when installing an inverted roof with a top layer of materials with low vapor permeability (earth, concrete tiles, etc.), it is necessary to provide a drainage layer over the extruded polystyrene foam that does not prevent the diffusion of water vapor, for example, a layer of crushed stone or fine gravel with fraction 4 -8 mm and a thickness of at least 20 mm (Fig. 7).

1 - overlap
2 - primer layer
3 - waterproofing carpet
4 - insulation
5 - filter material
6 - drainage layer of gravel
7 - paving slabs

1 - the main layer of insulation
2 - waterproofing carpet
3 - an additional layer of insulation
4 - filter material
5 - ribbed floor slab

In cases where the supporting structures of the floor are made of thin ribbed slabs of small thickness, condensation may form on the inner surface of the floor, due to the ingress of cold water under the insulation layer. To avoid this, it is recommended to provide for the installation of two layers of insulating material: one above the waterproofing carpet, the other (additional) - under it (Fig. 8).

Insulation of existing flat roofs

As one of the methods of insulating an existing flat roof, it can be recommended to transform it into an inversion roof. This type of insulation is possible only in the case of sufficient strength of the supporting structures. In the absence of leaks, a layer of insulation is laid directly on the surface of the waterproofing carpet, but if the waterproofing is in an unsatisfactory condition, it should be replaced or an additional layer of rolled waterproofing material should be laid. Slabs of extruded polystyrene foam are laid on the restored waterproofing carpet, on top of them there is a filtering material followed by a layer of gravel with a thickness of at least 50 mm (Fig. 9), it is also possible to arrange an exploited roof, as described above.

1 - surcharge gravel layer
2 - filter layer
3 - insulation
4 - repaired waterproofing carpet
5 - existing coverage

1 - floor slab
2 - primer layer
3 - vapor barrier
4 - insulation of the existing roof
5 - repaired waterproofing carpet
6 - an additional layer of insulation
7 - gravel backfill
8 - drain funnel
9 - wooden beam

Particular attention should be paid to the tightness of the waterproofing carpet in the place where the pipe passes from the drain funnel. If the existing roof did not have insulation, the funnel junction node is performed in accordance with Fig. 4 in the presence of an old insulating layer, the insulation material is selected along the perimeter of the funnel, and a wooden bar is placed in this place (Fig. 10).

Before inverting the existing flat roof around the perimeter of the covering, it is necessary to arrange a parapet with a height of at least 500 mm, which can be made of monolithic reinforced concrete.To do this, at the location of the future parapet in the reinforced concrete floor, holes are drilled into which the anchor rods are monolithic, The reinforcement frame of the parapet is connected to the anchor rods , install the formwork and fill the structure with concrete.

1 - floor slab
2 - primer layer
3 - vapor barrier
4 - available insulation
5 - waterproofing carpet G - new thermal insulation (extruded polystyrene foam)
7 - gravel
8 - drainage layer (gravel with a diameter of 4-8 mm)
9 - paving slabs (along the entire perimeter of the roof)
10 - a wedge made of heat-insulating material
11 - internal insulation of the parapet (extruded polystyrene foam)
12 - wooden beam
13 - fastening profile
14 - covering metal profile
15 - external thermal insulation of the wall and parapet
16 - hinged facade

Only after the parapet has been erected can work begin on the installation of the inversion roof. To exclude the possibility of freezing of the concrete floor, all surfaces of the parapet should be thermally insulated (Fig. 11).


Inversion roof pie structure

The basis for this type of roof is a reinforced concrete floor slab, just like with a traditional flat roof. The rest is quite different. An inverted flat roof, if we consider its structure from above, consists of the following main layers:

  • drainage (functional), which can be made with gravel, crushed stone with sand, fertile soil, a complex of sand and gravel bedding plus paving slabs
  • filtration, which is formed from geotextiles or other durable fabric that can freely pass moisture, trapping large solid particles
  • heat-insulating (sound-insulating) pillow, which is made of durable insulation
  • waterproofing is located below other layers, is arranged at a slope of up to 5 degrees and is located directly on the floor slab.

These are the main layers of the inversion roof pie, built according to the simplest scheme. In many variations, some layers are modified or reinforced with additional materials. For example, if the functional layer is formed from the soil for growing lawn grass, there can be several filter elements, and of different types. When inversion roofs are installed in regions with too hot or cold climates, special attention is paid to the formation of an effective thermal insulation carpet.

The simplest type of materials that form the drainage layer of the inversion type roofing are various bedding. More often, coarse gravel or crushed stone with a fraction of 25-35 mm is used for this, which is poured at least 50 mm thick. If a pedestrian zone is arranged on the roof, more often pavement-type tiles are laid on top (with seams that freely allow moisture to pass through), but before that, a bed of fine gravel or coarse sand is formed. In cases where a car park is made, reinforced concrete slabs of a small area are used as the material to form a solid surface. The most difficult drainage layer is the soil, intended for the construction of the green zone. In such a situation, the surface of the cake itself is multi-layered, where several carpets made of different materials can alternate.

As a filtration material, they are usually used, although profiled type drainage membrane sheets can be additionally laid. Reinforced filtration layers of the inversion roof cake are made with a ground cover, when it is important to prevent as much as possible the seepage of small ground particles to the heat-insulating carpet.

For insulation and sound insulation of the roof in the considered variant, dense polymer materials are used. Extruded polystyrene is generally preferred. This insulation is completely impervious to moisture and has a high compressive strength - characteristics that best meet the operating conditions and requirements in this situation. The thermal insulation layer is formed from 5 to 15 cm, which depends on the climatic characteristics of the region or the sound insulation requirements.

The lower, waterproofing carpet, is arranged directly on the floor slabs or on a pre-leveled surface formed under the required slope. Considering the importance of creating a reliable and durable hydro-barrier, it is formed in several layers using various types of waterproofing materials. Even if one waterproofing agent is used (usually roll deposited materials), it is mounted in several layers.

Important! An inversion roof is usually designed and constructed in conjunction with the building on which it is intended. However, nothing prevents the conversion of a traditional flat roof covering into an inversion one, if the margin of safety of floor slabs, wall structures and foundations allows it.


Types of inversion roofs

The design of the inversion roof cake may vary depending on the intended loads.

Gravel roof

The simplest variety that does not involve the operation of the roof. There is no finishing coating, but gravel backfill does not play the role of drainage, but ballast, pressing down the insulation. The fact is that the latter is placed in the inversion roof without fastening, allowing water to flow freely over the waterproofing carpet.

Large stones are used - 25–32 mm in size. The backfill thickness is 30–50 mm.

Roofs with gravel backfill must not be used.

Pedestrian roof

On such roofs, cafes, terraces, sports grounds and so on are arranged. The role of the finishing coating is played by paving slabs, laid on a bed of fine gravel (5-10 mm), sand or a mixture of these materials. Insulation is selected with a durability calculated not only for the standard snow load, but also for the weight of pedestrians.

When calculating the loads on a pedestrian roof, it is necessary to take into account the number of people simultaneously present on it.

Roof with greenery

In this type of inversion roof, double filtration is used: another layer of geotextile is laid on top of the crushed stone backfill. On the latter, a soil layer is poured for planting plants. Experts advise in this capacity to use a mixture of compost with vermiculite, expanded clay or perlite.

A green carpet protects roofing materials from temperature fluctuations and mechanical damage, while reducing the noise level

The top layer of the waterproofing carpet is made of a special root-resistant material.

Video: Principles of Building the Right Green Roof Pie

Roof for car parking

Increasingly, the roof of an apartment building is equipped with a car park. Distinctive features of this design:

  • insulation with maximum bearing capacity is used
  • a monolithic or prefabricated reinforced concrete slab is laid over the backfill (stones 25–32 mm in size)
  • as a topcoat, asphalt concrete is laid.
It is advisable to equip a car park on the roof in densely built-up areas where it is problematic to allocate a plot for ground parking

TechnoNicol Pie

The Technonikol company produces a wide range of materials for the installation of inverted roofs for any purpose, including rolled bitumen-polymer surfacing waterproofing materials:

  1. Technoelastmost B and Technoelast EPP. Roll waterproofing for general use. Due to the polyester base, it is highly moisture resistant. Has a layer of fine sand powder.
  2. Technoelastmost S. It is used in the upper layer of waterproofing carpet, when asphalt concrete is laid directly on it (in non-insulated inversion roofs).
  3. Technoelast-Green. A material that does not lend itself to the destructive action of plant roots. This property is due to two factors. The outer layer is represented by a thick polymer film, and an additive that blocks root growth is added to the binder. When arranging a waterproofing barrier, "Technoelast-Green" is laid only with the upper (outer) layer, the underlying (inner) ones are made of ordinary bitumen-polymer waterproofing, for example, "Technoelastmost B" or "Technoelast EPP".
  4. Technoelast EKP. The material has a shale powder on one side, which makes it resistant to solar radiation. "Technoelast EKP" is used in places where the waterproofing barrier exits to the outside, that is, when making connections to pipes and other vertical surfaces.
  5. Technoelast-Fix EPM. The material is intended for loose laying when it is not possible to glue the waterproofing to the base. In places of overlap, it is connected by welding.

Technonikol roofing cake uses products manufactured by the company

All materials to be welded (for example, Technoelast-Fix is ​​not such) are equipped with a low-melting polymer film. Upon reaching the required temperature, a pattern appears on it.

The company also offers:

  • bituminous primer, used as a primer before gluing roll waterproofing on a concrete or cement base
  • hot mastic No. 41, used for sealing cracks, chips and expansion joints
  • cold mastic No. 23, applied under the edge of the waterproofing carpet, adjacent to the vertical surface (above the pressure strip).

Drainage membranes are also known to builders:

  • composite membrane Planter-Plast - a polymer mesh, pasted over on both sides with geotextiles, can be used on asphalt roofs as a drainage layer instead of a crushed stone cushion
  • polymer membrane Planter-geo for pedestrian roofs.

The Technonikol company produces Planter Standart and Planter-geo waterproof polyethylene membranes, which completely exclude the ingress of moisture to the insulation. This increases the service life of the latter, because even extruded polystyrene foam with its low water absorption is gradually destroyed.

Geotextiles of the TechnoNIKOL brand are offered separately. Its density is 350–400 g / m 2. And this manufacturer produces extruded polystyrene foam under the trademarks "Technoplex 45" and Carbon Prof 300.

Pie with tiles

Pedestrian roofs are less susceptible to leaks if a cement-sand screed covered with ceramic tiles was used. The thickness of the screed is at least 50 mm, while cement grade M150 or more is used.The reinforcement mesh is tied from separate rods or a ready-made road mesh with a cell of no more than 150x150 mm is used.

Perform an inversion pie with tiles as follows:

  1. Roofing material or glassine is laid under the screed in order to keep the cement milk in the solution.
  2. From above it is coated in two layers with polyurethane mastic (it is protection from water).
  3. Then sprinkle with sand to improve adhesion. It must be dry. It is applied to the mastic immediately after laying the second layer (the maximum permissible thickness is 1.5 mm), until the composition has time to harden.
The floor of the flat roof terrace can be covered with ceramic tiles

Basic design requirements for roofs in use

When erecting roofs, it is very important to arrange expansion joints with a minimum width of 5–10 mm. The size of the areas between the seams is:

  • 6x6 m - for leveling cement-sand screeds
  • 4x4 m - for fine-grained asphalt concrete.

Expansion strips, 15–20 cm wide, are laid along the temperature-shrinkage joints. They are glued to both sides of the joints.

The waterproofing carpet can be laid directly on the surface of the insulation only, guided by the results of strength calculations, taking into account the ultimate strength and modulus of elasticity of the heat insulator. The adhesion of the roof to all protruding roof structures is protected from moisture by installing waterproofing on vertical surfaces by at least 25 cm.

In the case of operated roofs, drainage is provided internally. It is important to pay special attention to the junctions of the roof to the drainage funnels, walls and parapet. They must be carried out taking into account all regulatory recommendations.

The number of funnels depends on the catchment area and is determined by calculation. For example, for roofs with greenery, the maximum distance between drainage funnels should be no more than 24 m. With an area of ​​up to 500 m 2, one funnel with a minimum diameter of 10 cm can be made. Their design is selected taking into account the type of roof.

The exploited roof solves the problems of large megalopolises with a shortage of areas. Roofs with landscaping make it possible to enjoy all the benefits of nature, without leaving the city, and sometimes within your home.


Inversion roofing - technology, diagrams and materials

Flat roofing is not very popular with developers. And driving through the areas where individual housing is being built, it will be very difficult to find a private house with a flat roof.

This is due to the lack of confidence in this type of roof. It is generally accepted that it is almost impossible to perform reliable waterproofing of a flat roof, and over time such a roof will "leak" and require constant repair, but these are just unfounded assumptions.

In this article, you will learn:

Compliance with the technology at all stages will contribute to the reliability and durability of a flat roof, and properly executed waterproofing will allow the under-roof space to always remain dry and ensure comfortable living in such a house.

What is inversion roofing

In order to understand what an inversion roof is, let's remember what a pie looks like. conventional flat roof on the diagram:

So, inverted roof - it is the same flat, only according to the technology it has a reverse order of layers. In the following diagram, you can see how the inversion roof pie differs from the usual flat roof.

Thus, if we compare the two pies on the diagrams, it becomes obvious that the waterproofing layer of the inversion roof is located not at the very top, but under the insulation, thanks to which it is protected from the effects of various kinds of negative factors, such as ultraviolet light, temperature drops, etc. ...

What is an inverted roof for?

An inverted roof is a worthy alternative to a conventional flat roof, since there is a significant drawback in the cake of a conventional flat roof - the waterproofing layer is located at the very top and is constantly exposed to aggressive atmospheric phenomena such as precipitation, frost, ultraviolet rays, etc.

And given that the slope angle for flat roofs is about 3 - 5 o, the slightest violations of the waterproofing layer, even if the installation technology was followed, can lead to disastrous consequences.

An inverted roof is devoid of this significant drawback, its waterproofing layer is located not at the very top, but practically at the very bottom under the insulation and is protected from negative factors, which will significantly increase its service life.

What materials are used for the construction of an inverted roof

The device of inversion roofs involves the use of conventional materials, even in some cases, an inverted roof may end up being a little cheaper than a conventional flat one, because it will lack a vapor barrier, which is necessary in a flat roof cake.

Inverted roof waterproofing

The waterproofing layer is laid over the floor slab. Waterproofing materials can be used on a bituminous basis, the same as for a conventional flat roof.

Waterproofing is a very important element of any roof, and a roof with a minimum slope, like nothing else, needs a high-quality and reliable waterproofing layer.

You can also use more modern materials, such as various membranes, for example.

Insulation for the construction of an inverted roof

The insulation in the inversion roof cake should be such as to maintain the same temperature of the waterproofing layer located under it throughout the year, which will keep the waterproofing intact for many years.

As a heater for an inverted roof, it is necessary to use a material that practically does not absorb moisture. Such material can be expanded polystyrene or extruded polystyrene foam.

If nothing is planned to be built on the inversion roof, then a low-density insulation, such as expanded polystyrene, is also suitable. Well, if the inverted roof is operated, then the insulation should be denser, and in this case, extruded polystyrene foam (EPS) is ideal.

The drainage layer in the inversion roof device serves to drain water, as a drainage, and another very important purpose of it is to protect the insulation from mechanical stress and damage.

This layer is an indispensable element of a flat roof and is usually performed from gravel at least 5cm thick.

If it is planned to operate the inverted roof as a kind of terrace or garden, then it is necessary to additionally build layers of filtering material. This material is needed to prevent soil erosion above the inversion roof and to prevent soil from getting rooted into the main structure of the inversion roof. The filter material will allow water to pass through, but will retain soil and sand particles.

Inversion roof vulnerabilities

An inverted roof, like any other, has a number of vulnerabilities, the waterproofing of which must be approached with a certain rigor, these are places such as:

  • nodes of abutment to the parapet and walls
  • chimney connection
  • drain funnels

All these places must be strengthened in terms of applying a double layer of waterproofing in order to prevent various kinds of leaks.

In terms of technology, pitched roofs are naturally much simpler, but in terms of roof use, inversion roofs, and indeed any flat roofs, have a significant advantage - this is an original exploited roof.

Yes, by constructing a pitched roof, you can make an attic space under it, you can even make a living space, but a flat roof can be used much more original, there you can plant a garden, arrange a terrace, build an outdoor pool without thereby using the space around the house.


How to make a flat roof

The design of flat roofs looks very simple. The base for a flat roof is wooden or metal beams. They are placed on the walls of the building, and will carry the main load of the roof.

If we talk about the load, then it is important to understand that in winter a large amount of snow can accumulate on a flat roof, and this, in turn, gives a lot of additional weight.

Unfortunately, many builders with little experience do not think about this, and calculate the weight of the beams only on the weight of the roof itself and a couple of people.

Your best bet is to look around your area for flat roofs and do some research. This is how you will find out how to make a flat roofwhat material is best to use and what kind of load to envisage.

  • Flat roof plan
  • Flat roof construction
  • Wooden flat roof
  • Insulation of a flat roof

Flat roof plan

The main task of any roof is to drain rainwater or snow from the slope of the roof itself. If the installation of the pitched roof of the roof is done, then everything will be normal here, precipitation falls into the gutters, and then flows through the drain pipes into the street.

Flat roofs have long been used in construction. They are considered popular for agricultural buildings, production facilities and residential buildings.

Flat roof plan involves the conclusion of the building drainpipes, inside the building itself Using a flat system is when there is an intake slot in the flat roof and downpipe system.

The roof plan is divided into several options, which depend on the choice of a particular roof:

  • Standard flat roof.
  • Green roof.
  • Mixed roof option.

Standard flat roof - it is laid on an insulating layer. The weak side of this option is waterproofing, because it gets under the influence of precipitation and temperature changes. It is also affected by the load when walking.

For big cities, these roofs are considered the best. In megacities, as a rule, there are few undeveloped land plots. Using such a roof will allow you to build a cafe on top or, for example, a green area, and so on.

A similar exploited roof for an underground parking is made as follows:

1. A waterproofing layer is applied to the screed.

2. After this layer, a filtering and heat-insulating layer is applied. The most commonly used gravel. Sidewalk slabs are laid on it, and as a result, the usual courtyard area comes out.

Flat roof plan is becoming more and more popular for green roofs. That is to say, gardens and roofs are terraces on which large shrubs, trees, lawn grass are grown. You can use another way by creating a soil layer.

But the most difficult roof is considered a mixed version, when green areas need to be alternated with pedestrian paths. During the design of the roof, several systems are used. Popular are mechanical, inversion, ballast and adhesive systems.

The ballast system is usually performed on roofs with an angle of inclination of no more than 15%. You can use this system if there is a solid foundation under it, since the ballast will create a large load.

An inversion system is a kind of ballast system. The only difference between these systems is the waterproofing layer. In the inversion system, it fits under the insulation. Here it is necessary to use insulation that will not absorb water. This system will be ideal if you plan to create green spaces or a place to relax.

Mechanical system - mounted on complex roofing installations or on a slope of more than 15%. These systems are very lightweight. Their weight is approximately 2 kilograms per square meter.

If the slope is large, an adhesive system is used. It is also used if the roof has an irregular shape with many angles. It is done by gluing.

Flat roof construction

Flat roof construction mainly performed in areas where the amount of precipitation is low. This is especially true during the winter period, since snow remains for a long time on a flat roof in large quantities. Therefore, when heavy snowfall is observed, it is recommended to construct flat roofs, taking into account the high loads from the snow, using beams with a large cross-section and improving the fastening of the elements.

The slope of such a roof can be from three to fifteen degrees, but it is better to use a slope in the region of five degrees. To make the slope the way it is needed, expanded clay, slag or other similar materials are used in the insulation that regulates it.

The flat roof system of heated houses looks like:

  • Roll carpet
  • Lightly covered with metal strips or strips (pitch: 50-70 centimeters)
  • Bearing beams.

The slope of this roof is provided by the entire structure. Therefore, it is required to carefully monitor the installation and maintain the slope every 1.5 meters. You can also make not too steep truss frames, with a slope of about 10 degrees, installing them along the entire length of the roof, and fix the crate on them.

Flat roof system for heated houses:

  • Roll carpet
  • Bituminous primer to treat screeds
  • Created cement screed
  • Insulation (expanded clay, slag, etc.) - in this case, the main element for performing a roof slope. It should be laid in such a way as to gradually make a slope in the correct direction of the slope.
  • Roofing material with an overlap of about 15 cm
  • Lathing
  • Bearing beams (from 0.5 to 1 m) with a section from 100 × 100 mm to 150 × 200 mm.

Flat roof construction system:

1. Instead of wooden beams, you need to lay metal I-beams, the height of which is 12-15 cm. A solid boardwalk is laid on the lower part of the beams, and a layer of roofing material is laid on it.

2. The next step is to install a double, that is, in two rows of reinforcement cage (with a section of about 10 mm) along and across (cell size 20 × 20 cm). The reinforcing frame should not come into close contact with the roofing material.

3. Then all this is poured with concrete to a height of 15 cm, maybe a couple of centimeters less. If the weather is not cool, but hot, then it is better to cover the poured concrete with a foil made of polyethylene, so that it does not dry quickly, but smoothly and evenly. The film must be removed after three days.

4. If you do not have this film, then it is necessary to carefully monitor the drying of the concrete and, if necessary, it must be watered with water. When the concrete is completely dry, you will need to create a slope with insulation. Next, a screed is performed and a roll carpet is laid. That's it, the monolithic flat roof is done!

Wooden flat roof

Wooden rafters are the internal roof frame, which, as a rule, belongs to the oldest and most popular structures. They are produced in both wooden houses and brick houses with flat roofs.

What is the best rafter timber?

For construction wooden flat roof, you will need a coniferous tree - spruce or pine. They have common properties, namely: elasticity, strength, durability, resistance to the external environment. And such wood is considered very soft, which is easy to process. These types of wood are of low cost.

Fir wood can also be used, but it is less resistant to moisture with a low level of strength. Larch wood is considered the best choice. But this species is limited in felling, and therefore the cost of this wood is high.

To get a monolithic wooden element, you need to saw off the logs several times, after which their front and side parts will be flat and take the shape of a rectangle.

The moisture content of the wood must be at least 20 percent. Freshly cut wood with a moisture level of over 30 percent will be 60-75 percent less durable than dry wood, which, of course, reduces the strength of elements made from such wood.

For the construction of frames wooden flat roof, it is better to use wood of the first grade, since the use of the second and third grades is recommended after careful treatment with antiseptics.

According to the structure, the rafters are divided into inclined and hanging.

Inclined rafters are erected in houses with an average load-bearing wall or columnar intermediate supports. These rafters are erected if the distance between the supports, that is, the span itself, will not exceed 6.5 meters. The width, which is covered by inclined rafters, can be increased to 10-12 meters if there is one additional support, and with two additional ones - up to 15 meters. The location of the rafters directly depends on the size of the building.

Inclined rafters are easy to assemble.

Hanging rafters look like two rafter legs, which are in the same plane and are connected from below by tightening. These rafters are supported only on two supports, which are on the edge. The lower ends are supported by special bars called Mauerlat bars.

The wood or metal brace that connects the rafter legs reduces stress. It can be installed at the base of the rafters or higher.

For the construction of such a structure, pre-made rafters (separately) are installed on the attic floor, and then, with the help of additional elements, they are assembled.

If sloped and hanging rafters are installed over several spans of the same roof structure, then they can be erected in an alternating order. Where there are no intermediate supports, hanging rafters are used, where there are - inclined.

Insulation of a flat roof

Insulation of a flat roof can be produced by external and internal methods. It is worth noting that internal insulation is simpler, when the heat-insulating material is glued to the surface of the ceiling. The device of thermal insulation from the outside is somewhat more difficult, therefore, a professional roofer should perform this type of work.

In order for the room to be thoroughly insulated, 10 cm thick material is enough. For this type of work, it is more convenient to use mineral wool slabs, which are easy to put in a joint with each other, since they have a rectangular or wedge-shaped shape. When installing thermal insulation, special attention should be paid to the device of the vapor barrier layer.

The presence of a vapor barrier can be guaranteed by the existing gap between the thermal insulation layer and the roof covering or by the laid polyethylene film. The presence of a vapor barrier layer is especially important, since the temperature difference between the inner space of the building and outside it can lead to dampness, which is fraught with serious consequences not only for the roof, but for the entire building.

Before proceeding with the work on the insulation of a flat roof, it is necessary to find out in what condition its supporting structures are and, if necessary, bring them into proper form. At the same time, you should check the integrity of the wiring laid in the attic.

After completing the repair work, we begin the installation of the thermal insulation itself.

It is possible to insulate the outside of the flat roof of the building using rigid thermal insulation boards. Panels in the form of a solid base are placed on the beams of the supporting structure. Heat-insulating plates are laid on the panels, which are pressed down with any weight.

The seeming ease of performing this type of work at first glance is complicated by the fact that you have to work at height. In addition, special care is required when moving on a roof covered with roofing materials, since the slightest damage to them can lead to a leak in the future. Therefore, it is better to entrust this work to professionals.

Internal insulation of a flat roof (or insulation from the ceiling side):

In most cases, this is the best solution. The process of such insulation will not be difficult in itself. It is only necessary to solve the problem with the future lighting of the room in advance. It is better to choose fire-resistant polystyrene foam tiles as insulation, as a rule, they are glued to the ceiling, fixing wooden planks between them for greater stability.

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