Materials and methods

We repair and replace all types of flat roofs.

Flat roofs usually have a shorter life than slate or tile roofs. The cause of the failure is mostly due to cracks opening up in the felt surface joints. How big a repair depends on how much rainwater has penetrated the structure and for how long. If the roof has mineral wool thermal insulation this becomes soaked. The support joists may become rotted or deformed.

If there is no significant damaged to the roof deck the cheapest option for repair is to over-board it with 11mm thick OSB sheets (Oriented Strand Board) and then apply a new surface.

If the existing deck, usually plywood, has been damaged by long-term water penetration, then a new 18mm OSB deck is required. It may not be possible to ascertain the extend of damage to the roof timbers until the old deck has been removed.

When replacing the deck it is a good idea to also check if new mineral fibre thermal insulation is required.

The first choice for new surfacing is now EPDM Rubber. This is available in wide rolls so, on most roofs, there will be no joints, thus reducing the chances of future failure. EPDM Rubber is guaranteed by the manufacturer for up to 25 years.

Where it is not practical to use EPDM 2-ply or 3-ply torch-on felt will be used. This is laid with staggered joints between the layers to minimise the risk of joint failure in the future.

On roofs where there are steps or upstands and/or objects penetrating the roof (such as pipes, vents or roof windows) GRP (Glass Reinforced Polyester) may be the best option because of its drape characteristics. GRP coatings are made up of a sandwich of polyester resin and glassfibre fabric shhets. GRP is the most costly roof covering because of the materials and amount of labour involved.

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