Second Roof Layer

Roofing second layer of shingles roofing.

Second roof layer.

This provides added protection against ice dams. Use 1 5 or 1 75 inch roofing nails. A second layer of shingles only complicates the job when a roofer is trying to fix a leak. 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. Flashing around roof penetrations and sidewalls can be compromised. 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. How to shingle over existing shingles and how to shingle a roof how to install roof shingles shingle layout lines h.

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. That helps your final layer of shingles look flat with a proper installation. This will force you to replace your roof earlier than expected.

Add a layer of shingles over the newly repaired area before you install your second layer of shingles. Any more than that and you d have to tear off the old shingles before installing a new layer. However installing new flashings including special drip edge flashings made for reroofing will ensure a tight seal and a long life. Steep sloped roof products such as tile slate metal and shakes only allow one layer.

The savings you re going to see may be in the range of a modest 25. Most people would limit this practice to a total of two layers of shingles. On most flat roofs such as epdm tpo or modified it is perfectly acceptable to two layers of roofing. In fact the extra layer can reduce your roof s lifespan by up to 40.

The standard practice was that you could install a new layer of singles directly over the old layer during a re roof. 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. For many years it was acceptable to put even the third layer. This step is important because it brings the underlying surface back to a level height consistent with the rest of the roof plane.

That second layer of shingles won t last as long. 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. Adding a second layer could compromise the structure of your roof. That in itself eats away at the savings.