For dimensional shingles being installed over a layer of existing dimensional shingles you should always use a 1 1 2 inch roofing nail.
Roofing shingles over old.
Although many metal roof systems can be applied over an existing roof layovers are more commonly done with asphalt shingles.
Step 3 cover the old shingles.
Adding new roofing over old sometimes called a re roof is possible only with asphalt shingles also called composition shingles.
Beveled wood pieces called horsefeathers must be laid along the thick edges of the shakes to make a fairly flat surface.
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.
As long as it s done right and under the right conditions installing new shingles over old ones can last as long and look just as good as a complete re roof.
The felt should be secured every six inches with nails or staples.
You can t do it with wood or slate for example and you should never mix materials such as laying asphalt shingles over cedar shakes.
All shingle manufacturers honor the warranty whether their products are used for a reroof or a new roof.
Manufacturers will still.
Looks just as good and lasts as long.
In fact the only pro to a shingle over is it s cheaper and cleaner.
Although it sounds like a good idea we can assure you the cons heavily outweigh the pros.
When contemplating a new roof many people hope to simply do a shingle over and avoid the extra cost and mess of tearing off the existing roof and starting from scratch.
But before we get started one thing must be clear.
Choose a shingle style with the same dimensions as those on your.
Before you reshingle a roof read our step by step guide for adding new shingles over old ones.
Installing a new roof over shingles takes less time than tearing off the old roof.
Damaged shingles should be removed to check the decking for problems.
Asphalt shingles can be laid over cedar shakes or shingles however this is a roofing project best left to pros.