Second Roof Layer

Use 1 5 or 1 75 inch roofing nails.

Second roof layer.

Add a layer of shingles over the newly repaired area before you install your second layer of shingles. Flashing around roof penetrations and sidewalls can be compromised. Some roofers install a layer of waterproof shingle underlayment wsu over the existing shingles at the eave end as would be done for a roof laid on bare sheathing. Install the second layer.

Most people would limit this practice to a total of two layers of shingles. For many years it was acceptable to put even the third layer. Place the top of each starter shingle firmly against the bottom of the shingle immediately above it and even with the eaves then nail it into place. How to shingle over existing shingles and how to shingle a roof how to install roof shingles shingle layout lines h.

Steep sloped roof products such as tile slate metal and shakes only allow one layer. Another issue is that when you add in the second layer it can add extra weight to your roof. Often there is a problem with the first layer of shingles that was not apparent before the second layer was added. The second layer is also more difficult to install properly compared to new shingles.

This provides added protection against ice dams. That helps your final layer of shingles look flat with a proper installation. This step is important because it brings the underlying surface back to a level height consistent with the rest of the roof plane. Doing a second layer right means a lot of prep work goes into the overlay anyway and flashing which remember is the most vulnerable point on your roof is harder to guarantee.

In fact the extra layer can reduce your roof s lifespan by up to 40. This will force you to replace your roof earlier than expected. Adding a second layer could compromise the structure of your roof. Any more than that and you d have to tear off the old shingles before installing a new layer.

Plus depending upon the size of your roof you ve added multiple tons of weight which could pose a big problem if there is significant snow accumulation. A second layer of shingles only complicates the job when a roofer is trying to fix a leak. The standard practice was that you could install a new layer of singles directly over the old layer during a re roof. Asphalt shingles typically can have one more layer added over the top two roofs total.

On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing. That second layer of shingles won t last as long. The second layer of shingles will trap heat which can result in the decomposition of both roof layers. The savings you re going to see may be in the range of a modest 25.