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Metal roofing over asphalt shingles---furring strips, then metal????

prout35's picture

A few weeks ago I asked about applying metal roofing directly over asphalt shingles and was given reasons not to do that. Now I am still trying to avoid the task of removing the ashphalt shingles. There is no apparent leaking of the existing roof but the shingles are getting old.

So, can I nail furring strips to the existing roof over the asphalt shingles and then attach the metal roofing? Opinions please. Thank you.

I think you got a pretty good (post #202921, reply #1 of 1)

I think you got a pretty good answer here from your previous post:

Laying metal directly over

by seeyou in reply to prout35 [original] on Wed, 03/09/2011 - 05:59

Laying metal directly over shingles is a bad idea. The metal will move some from expansion and contraction and can rub the finish off of the back from grating against the shingle aggregate.

The typical solution to this is to lay a grid of 1X over the shingles and furring the grid straight. But this makes the eaves and rakes taller and can ruin the appearance of the structure and adds cost to the installation and makes future walking access a little tricky.

Tearing off the shingles allows for inspection of the roof deck at which time any rotten sheathing can be addressed. Also, it's tough to find any future leaks you might have since water that gets by the metal can run for a while on the shingles 'til it finds a hole.

Leaving the shingles on is false economy, IMHO.

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