Your Re-Roofing Options

Renewal of the roof covering may be necessary due to normal ageing, bad design, inadequate materials or poor workmanship: whatever the cause it is an ideal opportunity to consider improving its performance.

We have prepared this guide for householder’s and homeowners with minimal roofing knowledge. By providing information on the design, materials, construction and maintenance of successful flat roofs; we hope it will assist you to a satisfactory completion with your roofing project.

Renewal of the roof covering may be necessary due to normal ageing, bad design, inadequate materials or poor workmanship: whatever the cause it is an ideal opportunity to consider improving its performance.

Please Note: Refurbishment of a flat roof is likely to be reportable to the Local Authority Building Control (LABC) and approval must be sought unless the contractor is a member of CompetentRoofer (see page 13). Part L of the Building Regulations may require additional thermal insulation to all re-roofing projects where the roof underneath is heated e.g. a kitchen or bathroom. The required ‘U’-value is 0.18W/m2K. You should discuss converting to a warm-decked roof with your contractor and LABC. Here are some examples:

  • You have a cold roof and want to improve the insulation

The preferred option is always to convert to a warm roof by applying a vapour control layer, rigid board type insulation and new waterproof covering above the deck. Any existing roof ventilation can be closed off.

However, if there is existing insulation above the ceiling ideally it should be removed. If it cannot be the contractor should calculate how much new insulation is required above the deck to avoid condensation.

If there is no evidence of condensation, extra insulation could be added above the ceiling by removing part of the deck during the work. The thickness of the insulation will be governed by the depth of the joist and this may not allow sufficient insulation to meet the regulations. However, through-ventilation must be maintained and the clear space between the top of the insulation and the deck must be at least 50mm (2ins). It may be preferable to convert to a warm roof.

  • You want to reduce or remove ponding on the roof

Renewal of the waterproofing will not stop puddles forming on the roof. The best way to remove these is to re-fix (or renew as necessary) the deck on tapered timber strips called firings. Alternatively, if the deck cannot be disturbed, tapered insulation is available to create drainage falls on a warm roof.

  • You want to use the roof as a balcony or terrace

Such a change in use will increase the loadings on the roof and so the structure will have to be checked and improved as necessary. Seek specialist advice before proceeding with this option.

  • The existing waterproofing is reasonably sound but you wish to renew it in good time

Provided the roof drains and there is no evidence of condensation or structural movement, it may be possible to prepare the surface and cover (overlay) it with compatible materials without exposing the roof deck to the elements.