Author
Nigel Payne - Flat Roof Specialist
What Falls Does My Flat Roof Need?
Falls in flat roofing refers to the slight pitch which is almost invisible to the naked eye. The minimum fall for a flat roof is 1:80 which means that for every 80cm along the roof drops 1cm. To achieve a fall of 1:80 you may need to create a fall of 1:60 or even 1:40 since you may lose some of the falls to construction tolerances such as deflection in a tapered insulation scheme.
Why are flat roof falls important?
The purpose of falls in a flat roof is to ensure effective drainage and prevent ponding. Poor drainage and ponding can lead to deterioration of the waterproofing membranes, potentially effecting the roof’s longevity. Ponding water can also cause a build up of dirt, leaves and debris which can cause further issues if the gutters and drains become obstructed.
How to create falls on a flat roof?
There are several ways of creating a slight pitch in a flat roof. Firstly, you could create the falls at deck level by installing screed to falls or timber firrings. Screed to falls is a variable thickness screed that can be laid on top of the roof slab to give you the required pitch to direct rainwater off the roof. Timber Firrings are tapered pieces of timber which can be installed on the roof joists or the existing deck before installing a new timber deck on top. Alternatively, you could create the required falls by installing a cut-to-falls or tapered insulation scheme. Usually this will involve a site survey and design work to ensure the desired drainage outcome while also achieving the required u-value.
How can Bailey help?
Bailey technical representatives will check that falls are sufficient during a roof survey. If the falls are insufficient we will put forward the most efficient rememdial solution. Get in touch to book a free, no obligation survey to analyse the falls in your flat roof while also checking the overall condition of the existing roofing system.
