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How to Build a Flat Roof

Posted by BC Profiles on

If you’re looking to construct a flat roof on a property, it’s important to know the scale of the project, materials required and the process involved. Building a flat roof isn’t as daunting as some may expect and if you decide to take on the challenge yourself, we’re here to help ensure you have everything you need.

Please note: It’s always best to get the advice of a professional roofer before undertaking any project.

Right, let’s get started!

How to measure flat roofing

To find the square meterage of a flat roof, the width and the length of each plane on the roof should be measured and the figures multiplied together. This figure is the total area of each plane. If more than one plane is required, simply add the final calculations together and this will provide the overall size of the flat roof. Remember, the more accurate the measurements - the less you will waste in materials and costs!

Flat roof tool list

  • Roofing timber
  • Plywood
  • Steel joists
  • Exterior covering
  • Water-based adhesive
  • Foam with a fibreglass backing
  • Insulation

How to build a flat roof

The construction process begins by laying roofing joists across two upright items, typically the walls of the property or structure. These joists will provide the required stability for the roof and they are usually found in at least one wall. The distance between the to joists is around 400mm, although this does depend on the type of material that is going to be applied and the size of the roof itself. It also helps to reduce the amount of pressure that is placed on top.

The next stage is covering the joists with plywood, with the width in-between this determined by the weight that is placed on them as too much weight can lead to an unstable roof. Flat roofs should also incorporate a small incline in the design, this is added through the use of a frame and will ensure rainwater is sufficiently drained.

Decking and joists are them slotting together using tongue and groove fitting, this further enhances the stability of the roof and increases the integrity of the materials used.

Boards used for flat roofing must then be waterproofed with an additional layer of material used with a sealant to protect the inside of the building.

For advice and guidance on the tools needed for your flat roof construction, contact a member of the BC Profiles team today. Remember, we sell a wide range of roofline products including roof ventilation, roofing membrane, roof shingles and more, all in stock and at low prices.