When reroofing a trailer should you remove the first layer of shingles?

Building code allowed putting a second layer of shingle on top of old shingle .

But it is a bad practice.

The shingle price is only half and the labor is the other half.

2nd layer shingle would have much less life than 1 layer shingle. 2nd layer shingle are more likely to leak, curled up because the second layer trapped all the heat and curled up the shingle. Uneven shingle which is prone to leaking.

Right before we bought a 4-plex . the previous owner pay somebody to put a 2nd layer of shingle.

There is always a leak on that roof. and after 6 years of keeping trying to fix the leak from below the roof. we finally have the shingle torn out and changed.

SO in essence the 25 year warranty shingles only last 7-8 years because it never worked right for us. and the second layer shingle curled up badly because of the trapped heat caused by the extra layer of shingle.

my advice. just tear it down and reshingle the roof in 1 layer.

Always remove the old shingles. Besides all that extra weight, how would you ever know if there was a bad spot where the plywood might have gotten wet.

Yes, you definitely want to remove the old. That way if you want you can put down the new layer of black sheeting that can go under the sheeting. IF you do it above, it will be less even, and less likely to stop leaks - plus in the future if the bottom layer starts to peel up, your top layer would then also pop off....

we had a metal roof put on ours, and we didn't remove the shingles because its good for insulation