I am re-shingling my house. I have decided not to remove the old shingles since they are in good condition. Should I apply the felt underlayment before applying the new shingles? Thanks!

 

If you plan to use the same size shingle, metric or standard, don't bother with the felt. Just butt the top of the new shingles to the bottom of the old ones if they run straight. This will make your second course a little low but from then on they should fall right in line. Butting them keeps the roof smoother by laying the new shingles flat. If you are going to install a different size shingle, say metric over standard, you won't be able to butt them. In this case the felt is a good idea to give a smoother surface. To make it easier stick with the same size shingle. Some contractors prefer using T-lock shingles to roof over existing shingles. They are harder to find and more expensive but will not show irregularities from the roof underneath.

 

In fact, I'm using standard shingles over standard shingles. The old shingles are 3-tab, and the new ones are the architectural shingles. The old shingles are in decent shape, and laying flat. No leaking roof problems, so I guess I can just nail the new roof directly over the old shingles without using the felt. Thank you for your help!