Crumbling Bluestone on Foundation

lovetogardenFebruary 12, 2012

Hi Guys, I was out in my yard the other day and noticed something strange going on with my foundation. The bluestone slabs that cover the stone foundation seem to be crumbling. Since we've had a really mild winter this year I don't understand why this is happening. Any ideas how to stop it from happening or how to repair it? Here's some pics of how its crumbling and flaking away.

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Sophie Wheeler

Spalling like that usually means a porous stone that moisture has infiltrated and then frozen, creating the flaking. Look at the overhangs on your home to see if they are adequate to keep rain from the foundation,. Check the gutters. Check the weep holes to make sure they aren't plugged. Make sure the grading around the foundation carries water away and it's not sitting there sucking it up like a sponge. Check the actual foundation walls behind the veneer from the interior for any cracking or movement or out of plumbness that might be due to them being inadequately constructed.

If all of those things check out and there are no structural issues, then sometimes spalling just has to be lived with until it's bad enough to replace the veneer. Trying to seal the moisture out will cause more spalling rather than less as the sealers will trap moisture behind the surface.

    Bookmark   February 13, 2012 at 11:23AM
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Thanks Hollysprings, unfortunately, a lot of the reasons you suggested seem to be the case with this house that I just bought in August. I will be regrading in the spring. There are no gutters because where I live in the Adirondacks none of the houses have them. My house has a slate roof trimmed with metal for ice and snow to fall off easier. Fortunately, the blue stone is just an exterior cover for the stone foundation. Most houses around here that have stone foundations don't have that and have to get their foundation pointed ever few years or so.

I was wondering if after regrading I can use a hydrolic cement over the bluestone? Would you have any ideas on that? Thanks for your help.

    Bookmark   February 13, 2012 at 9:44PM
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Sophie Wheeler

You would not want to do that. Address the problems not the symptoms of the problem.

If your foundation is actual stone and not concrete with a veneer of stone, then you want to be very proactive in addressing the moisture infiltration issues that your home has or it could crumble and cease to provide support. Regrading will certainly help, but it needs to be coupled with the sufficient overhang or gutters. Just regrading won't do it. You need to investigate the moisture level under the house and take steps to minimize that. Yearly repointing should not be happening to your neighbors homes unless they too have moisture issues. Dry well affixed mortar will go decades between needing repointing.

    Bookmark   February 14, 2012 at 11:07AM
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The relatively mild winter is precisely the reason why this is happening. When the temperature is above freezing, water seeps into the minute spaces between the layers of which bluestone is composed. Then, when the water freezes it expands and causes flaking of the surface. This doesn't happen in winters where temperatures consistently remain below freezing.

With due respect to hollysprings, I would not follow her advice about gutters. There's a reason why your neighbors don't have them. In a really cold climate like you have in the Adirondacks with temperatures routinely in the -20 to
-25 range, gutters encourage ice dams on the roof - even metal ones - which are potentially much greater problems than the flaking bluestone.

By all means regrade if water does not run away from the house and keep an eye on the foundation from the inside, but I would not worry over much about the bluestone. It is, after all, a protection for the actual foundation and will endure minor flaking like this for a century or two. Putting anything on it like hydraulic cement is unnecessary and undesireable.

I'd also suggest that annual repointing of foundations is just common sense maintainence in a severe climate like yours - it doesn't mean that water is infiltrating the foundation - just moisture from condensation can damage mortar at -30 degrees.

What I would be careful about is making sure that no water is getting behind the bluestone. Trapped there, it could do some harm to the actual foundation and would eventually pry off the slabs.

All in all, your neighbors and other people who have lived in the Adirondacks - one of the most beautiful places on the planet - are your best source of information about what to do and not do.

    Bookmark   February 15, 2012 at 5:25AM
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