Expansive foam

Is there any guideline on how much of the expansive foam to use? I have a chimney and where it meets the concrete roof tiles the gap is too large for caulk or sealant. As a matter of fact I can fit two fingers along one edge and there is a small crevice under the tiles as well where they meet. Even though I am pretty sure there is flashing underneath I will still feel better if I can fill the crevice along the perimeter.
I thought I would use those foam that expands, however last time I used it I did a poor job of it and underestimated how much to use and it ended up expanding and cracking the surface I put on top of it. I wonder what is the best way to gauge how much to apply.
Thanks,
MC
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You could try and use some backer rod. This is a foam which is tube shaped and available on a roll. You stuff this into your gap first. Then fill up the remaining bit with caulk.
You can get this stuff at Home depot.
http://www.rd.com/content/openContent.do?contentId 689
Best, Mike.
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On Mon, 09 Jul 2007 02:29:27 -0400, MiamiCuse wrote:

Buy the window and door foam (blue cap) it expands about half of what the normal Stuff does.
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Do it right and foam isnt it. Its a job for a carpenter who can also flash it properly
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wrote:

Thanks. I did not explain clearly but this has nothing to do with the flashing. The flashing is installed between the chimney and plywood roof, then a layer of membrane on top, then the cement and concrete tiles.
There is no leakage in the roof either. The tiles were cut around the perimeter of the chimney, and the gap is like a almost two inches wide. Tree leaves fall in there and some moisture will go under the tiles (but above the flashing) and come out in the weep holes at the end. I just want to seal off this gap as well to prevent the leaves and water from getting under, but there is no leak through the chimeny roof joint which the flashing is protecting very well.
MC
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wrote:

That foam will actually absorb moisture and will certainly break down over time. It is not an effective barrier for water, not to mention it will degrade from exposure. Find another option. The foam is easy to apply, but it isn't going to offer any protection from moisture, in fact, it may even collect moisture.
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As Ransley said, flashing is the right way to do it. Here's an article on the way it should be done.
http://www.rd.com/content/printContent.do?contentId 758
I've yet to fix a leaking chimney that was done this way but maybe that's why they leaked, ya think? Ones I've done this way never leaked. Yep it requires time, work & tools.
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wrote:

Foam is not needed, imo. You are doing something cosmetic - I guess. The UV rays will eventually damage the foam...will it last.
Flashing underneath, sounds like my Spanish type tile. Barely nailed on :-))
Fix the flashing if need be, but my guess is the roofer never used foam... any area house...
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
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