How to Slope a Flat Roof for Drainage

With a new structure in the design stages, you need to know that your plan will work. If you are considering a flat EPDM roof for all part of your work, then a key issue is how water will drain away from the flat surface.

By definition, a flat roof has much less of a slope for the running off of water than a pitched roof system. This creates a kind of challenge when architects and site managers develop plans for their projects because they do not want the collection of water pools in some places and the water pool creating the possibility of a bulge or tear in the roofing material.

Despite this, many flat roofs are still planned and delivered daily worldwide. The reason is that technology has advanced to such an extent that the benefits of flat roofs can be enjoyed without this concern.

Flat Roofs

If you are told that one of the concerns when it comes to roofs is the danger of water pooling and the accumulation of other debris, then flat roofs would be completely avoided – certainly a pitched roof would be better? Thus, waste water would use its own momentum to fall from the roof and into the gutters.roofing

However, this would mean the end of the advantages of the flat roof: it usually works much cheaper at the site of construction than a pitched roof and a simpler design can be used for general construction, because of the foundation required for pitching. In addition, for the space below, you are not wasting any space to the slope of the pitched roof.

One of the reason why the flat roof has become a more viable option in recent years is the emergence of EPDM (Ethylene Propylene Diene Monomer), because it means that the rubber membrane within the roofing material is much harder and has a much longer life. Consequently, wear becomes less of a problem – and the attention can turn to the drainage.

Drainage – What are your Options?

This depends very much on how it is being used. If it is a small building with a flat roof, or a room with a flat roof on the side of a larger building, then the best practice is introducing a light tone to it – preferably a decrease of about 1 in 80 from the back towards the gutter, so that water will glide naturally down the roof and the channel into the gutters on one or more sides.

As far as the EPDM is installed properly, then the liquid impervious surface will encourage liquid to enter the channels, but an important point to note is that a projection at the gutter edge is required. By adding this projection, the water flows through the flat roof and goes straight into your drainage system. If you are not sure how to add this project, look at the cutting edge, which provides perfect drainage of flat roofs.

Normally, this simple flat roof will not be suitable for all applications; Sometimes a flat roof can be surrounded by pitched roofs, a wall leading to a level higher flat roof or other obstruction. Consequently, there is no side to act as the canal, raising the possibility of water pooling.

The solution is to get an angled roof drain or top drain, which act as a kind of plug hole for water to fall. Thus, while the roof can still be sloped slightly, it is intended at a smaller target.