Laying Flat Roof Felt the Right Way

Lead Image
  • 1-4 hours
  • Beginner
  • 250-750
What You'll Need
Roofing felt
Roofing hammer
1/2 inch Roof nails
Utility knife

When you have a flat roof is it important to put your roofing on correctly. The type of shingles you use should be laid down perfectly in order to keep water, snow, and ice from penetrating into the roof sheathing and rotting it away. The actual underlayment can help prevent a lot of problems. Laying roofing felt on a flat roof should be done in the correct manner as a preventive measure. Here is a step by step method for laying roofing felt the right way.

Step 1 - Clear Roof

Before you begin laying out the roofing felt, you need to make sure the roof is completely clear of any obstructions or debris. Use a push broom to sweep away any dirt and make sure you move any tools or materials out of the way of the felt.

Step 2 - Start At One Corner

Begin laying out your roofing felt by starting at one corner. Lay the roll of roofing felt on the corner and let it overhang by three inches on each side. Roll it out along the edge, keeping a three-inch overhang. Once you get to the edge of the roof, or when the roll runs out, start nailing the felt.

Step 3 - Secure Felt To Roof

After the roofing felt as been rolled along with the roof decking, you can begin to secure it to the roof. Use a W nailing pattern when nailing it off. Start in the corner and from there go in a diagonal six to eight inches from the previous nail and drive in another. Follow this pattern along the length of the felt.

Step 4 - Trim off Excess

Once you get to the edge of the roof again, cut the felt from the roll with a sharp utility knife. Finish nailing the end piece to the edge of the roof. Go around the edge of the roof and trim off the excess roof felt. Make sure it is secured tightly along the edge.

Step 5 - Continue Installing Roof Felt

After the first course is laid down on the flat roof, the rest will go pretty quickly. Start again in the same corner you started previously. Overlap the second course by four to six inches and secure the corners with roofing nails. Roll out the felt in the same way you did with the first course, keeping the same amount of overlap.

Step 6 - Cut Around Pipes

When you come to a pipe, or a vent, cut a straight line into the felt from the top and drape the felt around it. Once that course is completed, go back to the obstruction and lay a small piece over the area you made the cut. Spread out some roofing tar to make a seal.

Step 7 - Finish Roof

As you continue to lay out the roofing felt on the roof, continue with the overlap. This is the most important part of the process. The overlap of roofing felt will help protect the wooden sheathing underneath in case water does back up from the shingles. Trim off the excess on the edge of each course, and continue until the entire roof is completed.