Roofing Your Shed: Flat Roof Construction

Lead Image for Roofing Your Shed:  Flat Roof Construction
  • 8-16 hours
  • Beginner
  • 1,800-2,500
What You'll Need
Asphalt rolls
Roofing cement
Roof paint

A flat roof shed is the most common type of outdoor storage shed design. The flat style roof is often considered to be the most manageable form of shed roof construction and uses asphalt rolls as its roofing material. A flat roof shed will only require re-roofing every 10 to 20 years if it is maintained appropriately. Before any work is carried out, ensure that the shed roof is dry and clear of any debris such as protruding nails.

Step One – Underlayment

Start by placing a layer of underlayment over the shed roof. This will act as a protective membrane and provide an additional barrier against the weather. Underlayment can be made from polythene, fiberglass or even felt.

Start at one end of the storage shed roof and lay the underlayment material onto the flat roof surface, making sure that there are about 2 inches extra on either end to hang over the edges of the shed’s flat roof. The underlayment will not need to be bonded to the roof, as this will allow for movement without causing damage to the asphalt.

Step Two – Size

The asphalt rolls will need to be cut to the appropriate length. This will vary depending on the length of the storage shed, but it is important to make sure that the rolls are cut longer than required. The most effective way to achieve this is to measure the length of the roof, then cut a series of lengths from the roll. The asphalt will need to be overlapped during the application, so make sure that there is enough to complete the entire roof.

Step Three – Application

Start laying the asphalt rolls where the underlayment was first placed and leave an extra 2 to 3 inches hanging over the edge of the roof from all sides. This will provide a form of drainage for rainwater, which is essential to avoid a build of water on the roof. This could cause bowing or the shed roof to collapse. Overlap the asphalt. This will prevent any gaps being created in the shed roof construction.

Step Four – Securing

Tack the rolls into place. When the entire flat roof has been covered, use nails to secure the asphalt into place. The nails will need to be between 4 to 6 inches apart. Use roof cement along the edges of the asphalt for an extra layer of security and support.

Step Five - Protection

Cover the entire roof with roof paint. This will often be a tar-based solution and will ensure that the asphalt will last its maximum lifespan and is fully protected against the harshest of weather conditions.

Step Six - Maintenance

Inspect the shed’s flat roof either twice a year or after any bad storms to optimize its lifespan. Pay close attention to the seams of the roof where the asphalt has been lapped over. If there any gaps, fix them with roof cement. Also, make sure that there isn’t any build-up of water on the roof as this will become heavy and cause the roof to collapse.