June 9, 2023

How to Design a Flat Roof for Your Home

It used to be impractical to have a flat roof on the house. But the modern construction materials changed that and now they are as durable as sloped roofing. A flat roof is also something you can build by yourself with appropriate materials and knowing some basic information about this type of roofing.

Types of flat roofs

There are two general types of flat roof – warm and cold. There is a third type which is actually the combination of the two called warm flat roof with airflow. Each of them has a different design and you have to know them before you start construction.

The key difference is airflow between the roofing timbers also known as joists. Warm roofs place insulation in every place between the joists where there is airflow. On the other hand, cold roofs allow air to freely move between the joists and they don’t use insulation.

As you noticed, air plays an important role in the construction of flat roofs. That is why you have to create unblocked airflow when building a cold roof in order to avoid condensation. If your roof builds up condensation that can cause the wood to rot and ruin your roof.

Materials for flat roofs

The exterior surface of the warm or cold roofs is made from various materials and using different techniques.

Gravel and hot tar

Gravel and hot tar are the cheapest materials you can use in roof construction. You need to lay down three or more layers if you want to create a sturdy construction. Layers of waterproof material are placed in combination with hot tar and gravel.

Rubber membrane

Rubber membrane is ethylene propylene diene monomer material or EPDM which is actually the same one used for car tires. This is a very durable material that is glued to the roof which also makes it the easiest roof to build and thus it’s perfect to be a DIY project.

Modified bitumen

Modified bitumen for roofing is manufactured in rolls that are laid down in a single-layer on the roof surface. This is enough to create protection against ice and water, but you can apply a mineral-based surface on it to make it stronger.

Lead rolls

Lead rolls are durable roofing materials which can even protect you against radiation and also be used for soundproofing. Lead has a “high resistance to corrosion, durability, and long lifespan” points out Midland Lead, although this type of material will require professionals to install on your roof.

How to design a flat roof

The basic construction of the roof includes lying down of timbers on usually two walls positioned across from one another. A number of joists depend on the size of the roof, so calculate this before you buy any materials.

Then comes the decking or plywood used to cover the joists. Flat roofs are not entirely flat in order to avoid water and snow buildup, so make sure you design a slight incline in its frame. Therefore, when you install the decking take that into consideration as well.

Next step is waterproofing and the most usual material for this is EPDM rubber. It will cover the plywood boards and seal off any cracks or spaces between them. However, modified bitumen, lead, gravel and hot tar are also options you can choose if they fit your flat roof design.

In the end

When the time comes to build a flat roof, see if you can do it yourself or you will need to hire a professional. Even though it may seem like an easy job, the flat roof also needs some specific adjustments in order to serve its purpose. Design a flat roof so it will esthetically fit the overall exterior of your home and be functional at the same time.