If you want to replace your roof, you can save money if you don’t maintain the current roof and install the new shingles over it. However, you should know that a roof overlay (where you have multiple layers of shingles on the roof) comes with a few potential problems. Below are some of those problems.
Roof Overload
Roofing shingles are relatively heavy. One hundred square feet of shingles typically weigh between 150 to 240 pounds, but the weight can even exceed 400 pounds for some high-quality shingles. If you decide to have two layers of shingles on your roof, the roof will have to bear double that weight. The roof will get even heavier if it accumulates snow during the winter.
Unfortunate, many roofs don’t have the strength to bear all that weight. The damage might not be immediate, but the overload accelerates your roof’s wear and tear. In a worst case scenario (say if the roof support structures are weak) the roof might even cave in.
Hidden Roof Damage
A big advantage of a tear-off is that you get to see the condition of the roof structures under the old shingles. That way the contractor can gauge whether the support structures are damaged or can last many more years still.
If you opt for an overlay, you won’t know whether the structures under the roof are intact or damaged. That means the hidden damage can fester for a few more years and prompt premature roof replacement. The hidden damage also increases the risk of injuries to roofers or anyone who walks on the roof; they may fall through the roof if they step on a damaged area.
Moisture Trap
Moisture exposure accelerates the wear and tear or degradation of most roofing materials. That is why roofing contractors install a waterproofing barrier before they install shingles. Unfortunately, you can’t install a waterproofing barrier over shingles that are already on the roof.
Thus, if you decide on a shingle overlay, moisture can get trapped under the top shingles and cause damage. Before long, your roof may develop leaks due to the moisture issue.
Evenness Problems
Shingles manufacturers expect roofing contractors to install shingles over flat surfaces. The shingles need to lie flush on the roof so that they can’t allow water or debris under them and they can’t break easily too. If you decide on shingle overlay, the new shingles won’t lie flush on the roof because the top surfaces of the existing shingles are not exactly flat.
Warranty Problems
Shingle manufacturers understand the heightened risks of damage that roofs with shingle overlays face. Such risks may lead to premature damage that wouldn’t have occurred sans shingle overlay. Manufacturers can’t take the blame for such damages so don’t expect the manufacturer to pay for damage due to a double layer of shingles on the roof.
Future Double Tear-off
If you want a shingle overlay to save money, then you should know that the overlay decision only delays the inevitable task. Since you can’t have more than two layers of shingles on the roof, you will have to tear-off both layers the next time you want to replace the roof. You will use a lot of money for the replacement since double tear-off costs more than a single roof tear-off.
Issues with Some Shingle Type
Lastly, not all shingles qualify for the overlay option. In particular, don’t expect to overlay your roof if you have dimensional shingles; in that case, you must tear-off the current roof.
Talk to Cloise & Mike Construction Inc if you want to replace your roof. We will work with you to ensure you get the best possible roof for your house at a reasonable budget. Since good roofers are always busy, start your roof replacement plans in advance to get the best service.