Flat Roof Condensation Risk Analysis

With a cold flat roof construction it is critical that a minimum of 50mm of cross ventilation is provided underneath the roof deck.

Flat roof condensation risk analysis. This is something we do for all our new roofs as well as part of our design service. Factors to take into consideration when designing out the risk of condensation include. Avoidance of gaps in the insulation. As long as the roof accords with good practice then a more complex calculation method should not be necessary.

Avoidance of cold bridging. If the dew point is within the buildup you have a problem. Each of these constructions have draw backs to the building designer. In order to predict any potential condensation before installing insulation a condensation risk analysis can be performed.

Determining the risk of interstitial or surface condensation in a building depends on the components of the assembly the order in which they appear in the construction the building s use and its geographical location. While a flat or low slope roof can offer a long service life 20 years or more a small mistake can lead to a big leak. Flat roofs and low slope roofs also face potentially serious condensation problems that can in turn lead to costly rot or mold damage in buildings. A flat roof should be designed to minimise condensation and a condensation risk analysis should be undertaken taking into account positioning of insulating materials vapour control layers ventilation thermal insulation and the choice of materials.

Because the waterproofing layer constitutes a vapour control layer on the cold side of the insulation there is a high risk of harmful interstitial and surface condensation on the underside of the deck or the upper surface of the insulation. Condensation can substantially reduce the performance of insulation and could affect a building s integrity. This is to minimise any risk of harmful condensation. This type of roof has normally been used over small extensions to dwellings using timber joists and plywood deck.

Get an interstitial condensation risk analysis carried out. The analysis will determine the dew point and you can check where the condensation is happening in the report. This can be calculated using computer programmes. This takes into account winter condensation and summer evaporation.

If anybody is to make a judgement on the levels of workmanship and whether it makes the construction method any more acceptable for a particular project it should be the designer building inspector or end user.