Mystery Bulges Under Siding


Old 07-07-15, 09:30 AM
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Mystery Bulges Under Siding

Our 1961 home has developed bulging areas under its asbestos cement shingle siding. They are on the north and south sides in a horizontal line that coincides with the first and second floors. They are not all the way across. One was here, although less severe, when we purchased the home 17 yrs. ago but wasn't in the inspection report. That spot (photo below) was the site of cable installation and I'd guessed it was that. Now another has pushed a shingle off (above) and the protrusions are hard not spongey. There are hot water baseboard heaters along these areas but when I asked the plumber if they could be a cause he laughed it off as impossible. Before somebody goes tearing into the walls either from outside or inside, does anybody have an idea what it could be?
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Old 07-07-15, 09:59 AM
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Hi Mary and welcome to the forum,
The pros will be along shortly, but my first thoughts are moisture as you have already mentioned. I installed that old asbestos siding many years ago, but I don't remember if it had a left to right spacing requirement. Some materials will expand and when installed a small gap is required. Do the shingles that came off appear to fit the vacant space or are they a tight fit, side to side.

But that still leaves the question about the rim joust between the floors, why just there?

I'll watch to see what others suggest.

By the way, when an opportunity comes along it would be good to replace that (asbestos) siding. Just an 8 letter word you don't want attached to your house.

Old 07-07-15, 12:59 PM
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Fixing this will obviously involve removing the siding, so rather than beating around the bush or asking for opinions I would suggest you bite the bullet and just remove a few pieces, and see what's going on there. Removing the siding without breaking it is a little tricky. 2 methods: 1). Get a nail puller pliers and try to get on the heads of the nails and gently rock the pliers to loosen the nail... but support the pressure of the pliers by slipping a 6" wide flat putty knife (or similar) under the siding. If you have to nip the head of the nail off, so be it. 2). Use a multi-tool with a bimetal blade to get under the lap of the siding and cut the nails off from behind.

If you are really careful, you won't break the siding. My guess would be that a board used as sheathing is warping from moisture, especially if that piece of siding above has been missing for long. The fact that it's directly above this area is no coincidence.

Similar replacement shingles can be purchased from Home Depot, it's called GAF Weatherside.

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