The new shingles are applied over the existing layer of shingles.Â While overlays save on time, labor and disposal costs, they can only be done if certain conditions are met.
First we remove all the old shingles from the roof.Â Then we inspect your roofing deck (the wooden base over your rafters) and replace or seal it as needed.Â We then completely re-cover your roof with new underlayment and shingles from top to bottom.
If there are already two layers of shingles, an overlay is NOT an option, as Nevada County only allows up to two layers.
If you only have one layer, the existing roof is in good condition, lays flat (no bumps or rolls) and has no leaks or any problems with the underlying roof deck (soft spots), then an overlay may be the best option for you.
However, a tear-off will probably be necessary if:
The condition of the existing shingles is so rough and distorted that it would not be practical to flatten all raised areas enough for the new roof to lay flat.Â Installing shingles over existing shingles that aren't flat can make the new roof look bumpy and make it harder for the new layer of shingles to form a seal.
The roof structure shows signs of sag across the ridge or truss lines.Â If the roof does not look straight and feel solid, there may be structural defects.Â Shingles are heavy, and adding a new layer over an existing roof adds weight to the rafters and to the structure in general. Older roofs, sagging roofs or substandard rafters may not safely bear the additional weight.
If spongy areas are noticed when walking on a roof, or an inspection of the deck reveals rotted/warped wood or large gaps between the deck boards.Â Any rotten or damaged boards must be replaced before applying the new shingles.Â Deterioration can occur when there is delamination in the plywood due to glue failure.Â Dry rot is wood rot caused by certain types of fungi and if it isn't taken care of, it can spread. If there is any suspicion of bad decking, then a full tear-off should seriously be considered, as these conditions are not always evident until the roofing is removed.
Lastly, if you are considering the benefits of the Owens Corning Preferred Protection Limited Warranty, a tear-off is required to qualify for the warranty.
The experts at Gold Country Roofing have decades of experience installing quality roofs, both overlays and tear-offs.Â Contact us today for your free roof estimate, and we will give you our recommendation based upon the condition of your current roof.