How To Install Flat Roof

How To Install Flat Roof System

Like any part of a building’s exterior, flat roof installation should be constructed to withstand natural and human forces with the minimum of attention. In a flat roof installation, the waterproofing is always supported by a structural roof deck. This is usually a timber boarding of some type, which in turn is supported on joists. The ceiling, if any, is fixed directly to the underside of the joists.

Some specialized insulations can also be placed above the waterproofing, but this sort of construction is commonly confined to commercial and industrial buildings and has very seldom been used on residential buildings. In almost all cases where RBM has been installed, the surface of the waterproofing will need protection, both from ultraviolet light and from fire from external sources. The Building Regulations lay down the degree of protection required in the case of fire. This can be achieved by adding a layer of mineral chippings bedded in the compound to the surface of the roof, or by using a mineral surfaced layer of RBM as the top coat, or ‘Capsheet.’ Liquid applied and Single layer systems have this protection built-in and do not require additional protection.

Types of Flat Roof Installation Systems

  1. BUR.
  2. Single Ply Membrane.
  3. EPDM.
  4. TPO & PVC.
  5. Modified Bitumen.
  6. Metal Sloped Roofing.


The following general guidance can be confirmed by the specific membrane manufacturer.

The Protection from the Wind 

­ All roofs, including insulation and membrane, should be constructed to resist wind forces. ­

An experienced contractor will be able to advise. Seek his advice if your roof is particularly exposed.

The Protection from foot traffic ­

Materials should be selected to suit roof usage. If regular foot traffic is expected a surface protection must be provided. ­

If the use is changed, e.g. to a roof terrace, the structure may have to be strengthened.

The Protection from Fire ­

Consult your local authority if you are planning a new flat roof. ­ Most flat roof systems will meet the Regulations, but check with your roofing contractor.

The Protection from elements of Rain and Snow ­

The finished roof should have a slope of at least 1 in 80. To achieve this, a design fall of 1 in 40 or 1 in 60 is advised. ­

It is best to drain the roof to one or two edges. ­

Conventional gutters are better than internal outlets. ­

Internal outlets should be adequately sized to deal with storm conditions and be fitted with leaf and gravel guards. ­

The waterproofing should extend up adjacent walls at least 150mm (6in) from the roof surface in all situations. ­

The top edge of the waterproofing system should be protected by a cover flashing appropriately to the membrane.

The Protection from the Sun and Frost ­

It pays to insulate: heating bills are lower throughout the year and rooms are cooler in the summer. ­

Insulation of new flat roofs must satisfy the Building Regulations. Since April 2006, this also applies to the refurbishment of flat roof install.

Bitumen membranes should be protected from the sun.

The Protection from Condensation ­

It is essential that cold roofs include adequate through-ventilation of all joist voids etc. ­

Warm roofs always require a robust vapor control layer (VCL), bonded directly to the deck.

Flat Roof Maintenance

WTorres Roofing Company Recommend: ­

Limited access unless the roof is designed for it. If random access is required, e.g. for window cleaning, make sure that temporary boards are used unless the roof surface aims to accept it. ­

Inspection twice a year, in the months of March and November. Try to do one inspection soon after rain; it is best to see how well the water is draining away.

Before attempting any roof inspection, please ensure that access is entirely safe and that if a ladder is necessary, it is well secured. If you are unsure, call a professional roofer. If you are uncertain of the condition of the deck, do not step onto the roof and call us.

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Contact us today to learn how a roof service can revitalize your property. We proudly serve commercial, industrial, and residential customers throughout Dayton, Beavercreek, Kettering, Bellbrook, Oakwood, Centerville, Fairborn, Huber Heights, Miamisburg and throughout Montgomery County, Greene County, Warren County and Clinton County areas.