How Much Should Roofing Felt Overlap

Roofing felt is required to overlap 2 inches over the lower felt course.

How much should roofing felt overlap.

Ensure that the felt lies flat and smooth before securing it. Work up the roof to the peak and fold felt over the top overlapping at least 3 inches and fasten it on both sides. The overlap of 3 8 should be followed consistently for a smooth look once the shingles are installed. In other words if the height of the roof drops by 2 inches for every 12 inches in length you will need to use sealant to strengthen the overlap barrier.

Tack the roofing felt down with 1 4 staples using an air compressor with a pneumatic stapler a hammer tacker or a staple gun every 12 inches. A conventional roll of felt is enough for 432 square feet. Some roofing felts are actually glued down. Take your second length of felt.

However you must allow for overlaps on joints. These applications are ideal for flat roofs or protective surfaces under roof level decks. Make sure you have enough roof felt you don t want to have to stop mid way through the project to buy more felt. Therefore a 2 inch overlap provides redundancy at the edges where the barrier is weakest.

Do the other side of the roof the same way also with an overlap at the peak. One roll of conventional 15 felt covers 432 square feet 40 1 m 2. Must be installed at the rakes and eaves of the roof. The drip edge should extend at least 2 inches on the roof.

Using a downwards brushing motion firmly press the top layer of roofing felt onto the adhesive taking care to ensure that the strip of felt does not ripple or crease. Position this strip so that it overhangs the top of the first sheet by 75mm. Purchase an extra pack of felt in case you need more or end up damaging your first roll. The overlapping felt creates a secondary barrier for moisture and wicks water away from the shingles above and the sheathing below.

If lap sealant is used simply apply a bead of sealant on top of the underlap ridge going all the way down the length of the ridge before the overlap ridge of the next panel is placed on top. The bottom course of felt on a roof called sarking felt ensures that all of the rainwater is correctly channeled into the gutter by protecting the eaves from any wind driven rain. The vertical leg of the drip edge should be at least 1 5 inches wide and extend at least 0 25 inches below the sheathing. Trapped behind the guttering or if it is badly weathered it needs to be replaced.

Since you will have overlap between rows this works out to a total coverage area of 400 square feet the dimensions of a 20 x 20 roof. Nail along the top of this strip at 500mm. Where the sheets overlap apply roofing sheet adhesive using a disposable brush. Adjacent pieces of drip edge should overlap at least 2 inches 51 mm.