Re roofers have tricks to lay new roof shingles over old so that the same step ups between courses are maintained but if any old shingles are cupped curled or otherwise misshapen those defects will telegraph through to the new layer.
Roofing over existing shingles.
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.
The rest of the shingles are full width.
Why installing new shingles over old shingles can be good.
However installing new flashings including special drip edge flashings made for reroofing will ensure a tight seal and a long life.
Leak around a dormer which the homeowner never knew about long term effects of shingling over shingles.
Let s start with the good.
Its front edge is even with the front edge of the drip edge.
In a reroof job a special type of drip edge flashing is installed at the eaves and rake to wrap around the existing shingles.
When roofing over your existing shingles can be a good idea.
The starter course or strip is rip cut so it butts up against the third courseof the existing shingles.
All shingle manufacturers honor the warranty whether their products are used for a reroof or a new roof.
This can lead to increased rot mold and decrease the structural integrity of your home.
Add a new layer of shingles which means that the old roof will not be removed teared off.
Roof over shingle over has its place there are always factors to take into consideration before starting a project.
Many arizona homeowners with shingle roofs do decide to roof over their existing shingles because.
In a shingle over if some of the decking has buckled and warped over the years it likely isn t going to be noticed and fixed.
Plus the hours of labor go down and less equipment is used which lowers the cost even more.
Hope you like it.
Roofing over an existing roof is also called reroofing or an overlay.
If the job is done correctly with the new layer of shingles laid flat over the existing shingles the old roof cushions the new one and serves as a secondary barrier should wind or water ever break through the new shingles.
When you should tear off your roof and start from scratch instead.
This provides added protection against ice dams.
You can save money because there s no dump fee for removing your old roofing and there s no need for additional felt paper over the old roof.