The main purpose of the roof is to protect the rooms below from external precipitation. If in pitched roofs these functions are performed by roofing coverings made of various types of materials, then in flat ceilings the main load on hydraulic protection falls on waterproofing.
Also, the waterproofing carpet of a flat roof is most susceptible to damage, especially when it is located outside. In this case, an effective method for eliminating leaks is to repair the roof waterproofing using methods and materials comparable to the final roof covering.
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Why is it necessary to repair roof waterproofing?
Although the main negative consequences of damaged roof waterproofing are obvious, it is worth recalling them to justify the need for repairs. So, damaged roof waterproofing leads to:
- Leaks and flooding of lower rooms.
- Wetting and damage to the mineral wool insulation, if any. As a result, the thermal insulator loses its heat-protective properties, rots and becomes moldy.
- Damage to building materials under the roof: wooden rafters and slabs, ceiling coverings, ceiling and wall finishes.
Main types of roof leaks
Types of roof leaks are directly related to the design of the roofs and their roofing pie. Depending on the type of roof, they can be divided into the following groups:
Pitched roofs. In pitched roofs, the main type of leaks is through the depressurization of screw fasteners of corrugated sheets (slate), composite or metal tiles.
If the final covering of the pitched roof is flexible or rolled shingles on a bitumen base, leakage may occur due to its peeling as a result of the loss of the properties of the bitumen adhesive compositions.
Also, with small angles of pitched roofs, moisture may be blown under the piece roofing coverings during strong wind loads.
It should be noted that the main type of waterproofing for pitched roofs are special vapor-permeable and waterproof membranes made of synthetic materials (TechnoNIKOL Alpha). They are laid on rafters under corrugated sheets, any types of tiles, and metal strips of standing seam roofs.
Also, special bitumen-polymer lining carpets (TechnoNIKOL Andeper) are used for waterproofing pitched roofs. Since all these waterproofing materials are under the roof covering, the probability of their damage is negligible, as is the need for further repairs.
Flat exploited roofs. This type of roof is not so common in individual housing construction due to the high cost and complexity of installing a multi-layer roofing cake.
Usually such a roof is made insulated by fusing two layers of bitumen roll waterproofing onto a concrete base made of slabs. Then, insulation, slope-forming layers of extruded polystyrene foam, expanded clay concrete or cement-sand screed are placed on the waterproofing carpet.
The roofing pie, depending on the finishing coating, may include polyvinyl chloride, polyethylene profiled (Planter) membranes, and layers of bitumen roll waterproofing. Natural or artificial lawns, crushed stone and gravel backfill, ceramic granite, paving slabs, decking on wooden joists are most often used as finishing coating for exploited roofs.
It is obvious that with any roofing pie device, the waterproofing carpet of the exploited roof made of fused polymer-bitumen rolls is under many layers and is reliably protected from mechanical damage. Its only problematic place is the junction between the horizontal reinforced concrete base and the vertical walls of the parapet.
It is highly likely that problems in this area can be avoided by following the basic rules for installing fused rolls: installing smoothing fillets in the corners of the abutments and laying the sheets on the parapet.
Flat non-exploited roofs. This type of roof is the most vulnerable in terms of possible damage to the waterproofing, which most often occurs when clearing the roof of houses from snow.
This is primarily due to the fact that waterproofing in such roofs is located on the surface. The second problem is insufficient physical and, in some cases, temperature and anti-ultraviolet resistance of waterproofing materials, the main ones being:
- Bitumen, bitumen-polymer rolls, laid by fusion or on their own adhesive side.
- Polyvinyl chloride (PVC), thermoplastic polyolefin (TPO) membranes. Most of them are installed using the technology of soldering edges with a heated construction hair dryer. Much less common are PVC membranes, the joints of which are connected with glue.
- Mastics. This is the widest range of materials on bitumen, bitumen-polymer, polymer bases. Polyurethane or latex, which is, in addition to bitumen, the second main component of liquid rubber, are most often used as a polymer.
Materials for roof waterproofing repair
A wide range of materials are used to repair damaged waterproofing, the choice of which is directly related to the type of coating that has become unusable. Most often, roof waterproofing work is carried out using materials made from the same components as the waterproofing coating.
Waterproofing tapes
Bitumen-based adhesive tapes are a universal material for repairing pitched and flat roofs. They can be used to seal leaks in places where individual roofing materials are attached to pitched roofs, as well as damaged areas, and joints of bitumen rolls that have lost their tightness on flat surfaces.
A typical representative of sealing tapes is the Nicoband product from TechnoNIKOL Corporation in the form of strips 50-300 mm wide and 3000 mm long. The bitumen adhesive binder of such tape is protected from ultraviolet radiation by a special synthetic film of different colors to match the color scheme of the roof, foil or copper coating. To prevent sticking, an anti-adhesive film is placed on the sticky side of the tape.
Mastics
A distinctive feature of mastics is the ability to form a completely waterproof membrane on the surface, which has high adhesion to the base. Using bitumen, bitumen-polymer and polymer mastics, you can repair not only individual sections, but also the entire damaged roof made of bitumen rolls without dismantling them. To do this, you only need to cover the surface being treated with two layers of mastic waterproofing.
With the help of modern polymer mastics of the Hyperdesmo brand, it is possible to repair damaged areas of PVC or TPO membranes. This method is much simpler and more effective than similar work using the fusing of individual fragments of membrane sheets.
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Roof waterproofing repair technology
Since various materials can be used to repair damaged roof waterproofing, it is rational to consider the technologies for using their main types.
Using a sealed self-adhesive tape
Self-adhesive sealing tapes can be used to repair any roof made of natural (ceramics), flexible and metal tiles, slate, roll materials, as well as folded roofs.
- Self-adhesive sealing tape Nicoband is used according to the following technology:
- Work is carried out at an ambient temperature (base) of at least +5 °C. If the tape is used on surfaces heated by the sun, their temperature should not exceed +80 °C.
- The sealed area is cleaned of dirt and degreased using any organic solvent. To achieve high adhesion, the base must be completely dry.
- Using a painting knife, cut out a piece of tape long enough to cover the damaged area or hole by 30-50 mm from its edges.
- Then remove the protective film and place the tape on the damaged area.
- At the end, the glued piece of tape is rolled with a silicone or rubber roller.
Bitumen and bitumen-polymer mastics
Bitumen binder mastics are a universal material for repairing roof waterproofing made of similar bitumen-containing materials or rolls. They can be used to completely cover a roof with numerous leaks without dismantling the old roll waterproofing or to carry out spot repairs. When using the latter option, proceed as follows:
- At the site of leakage, peeling or swelling of the bitumen roll, make a cross-shaped cut and bend the edges of the sheet upward.
- Clean the area under the folded edges of the roll and lubricate it with bitumen mastic.
- The edges of the roll material are pressed again, coated with mastic on top and a piece of reinforcing fiberglass mesh or geotextile is laid.
- Cover the reinforcement on top with another layer of bitumen mastic.
When using bitumen mastics on roofs, it should be borne in mind that most of them have low resistance to ultraviolet radiation and require additional protection. These can be either special mastics with aluminum powder (TechnoNIKOL No. 57) or any ultraviolet-resistant paint and varnish coatings.
Polymer mastics
Using special polymer mastics Hyperdesmo PVC or Hyperdesmo TPO, it is possible to repair roofing made of corresponding polyvinyl chloride or thermoplastic polyolefin membranes. The technology of their repair with mastics consists of the following operations:
- The work is carried out under environmental parameters such that the membrane surface temperature is at least 3°C higher than the dew point.
- Clean the damaged membrane area from dirt using household chemicals, then rinse thoroughly with water.
- Mix the special Primer PVC (Primer TPO) primer with a low-speed drill and apply it to the areas to be repaired using a brush or roller.
- After the primer has dried, the repaired section of the membrane sheet is covered in one or two layers of Hyperdesmo polyurethane mastic (Hyperdesmo System), using a roller or brush to apply it.
Conclusion
Most often, repair work is required on the surface waterproofing of unexploited flat roofs, which is damaged when utility services clear the roofs of snow. In pitched roofs, the most hydraulically vulnerable places are the fastening points of the individual coverings.
The main materials for restoring the waterproofing of flat roofs are bitumen and polymer mastics. The final coating of pitched roofs is usually repaired with adhesive tapes.
