tuckpointing foundation

kitokoOctober 11, 2006

Our limestone foundation needs tuckpointing. Any suggestions on how or where to look for a contractor?

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Check your yellow pages for a restoration specialist....if they don't have somebody who does it ask them for a recommendation.....that's how we found the guy who did our chimney.

    Bookmark   October 11, 2006 at 1:07PM
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Not to sound like a commercial, you might want to try ServiceMagic.com They have a lot of pre-screen contractors with different specialties.

    Bookmark   October 11, 2006 at 4:49PM
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-a limestone foundation should be tuckpointed with a mortar mix that includes "type S" lime, also known as "dolomite lime" or "dolime." This mortar mix will comform to the cracks and crevices, and it is somewhat soft when cured, which helps to preserve the limestone foundation blocks.

    Bookmark   October 12, 2006 at 9:45AM
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This is going to sound very nit-picky straight out of the gate, but I'm wagering what you want is not tuckpointing but REpointing. Tuckpointing is actually a type of mortar joint in which the main mortar is the same color as the masonry. A thin groove is then raked out, and a very thin ribbon of a contrasting color mortar is laid into the groove. The result is the appearance of a much finer mortar joint than what really exists. Repointing is the act of raking out loose or failed mortar and replacing it with a joint profile that matches what was there before.

OK, stepping off my soapbox. :) (I can't help it, I try, but I can't). As you screen contractors for historic masonry work, ask them the following questions--and expect similar answers to those I have posted below:

1) What type of mortar mix will you use? "Lime-based, after we conduct a mortar analysis to find the appropriate ratios of lime to sand." If they talk about a typical mason's mortar or Portland cement, send them packing. Those are too hard and can do much more harm than good. The proper mix is a lime putty/sand mix. For most mortars the ratio is somewhere around 3 parts well-graded, sharp sand to one part well-aged lime putty.

2) How would you go about preparing our limestone foundation for repointing? If they mention an acidic cleaner of any sort, it's a red flag. Acid will etch limestone and, worst case scenario, can actually disintegrate it. Also avoid any discussion of any type of "blasting" from sandblasting to high-pressure water blasting or media blasting of any sort. If something is moving at that high a velocity toward your foundation, it can damage it, no matter how soft the media may be.

3) How will you prepare the joints for the new mortar? "We will rake out the loose mortar by hand, then brush out any dirt or debris, then thoroughly wet the wall down so your new mortar is able to retain its moisture as it cures." If they talk about raking out the existing mortar with power tools, question them very carefully about their methods. Power tools can muck up historic masonry in a heartbeat if the contractors are not extremely careful. After the loose mortar, dirt, and debris are removed, the wall must be thoroughly wetted so that the masonry and old mortar don't suck the moisture right out of the new mortar, turning it to sand. The mortar must also be kept moist as it cures.

4) (Depending on what area of the country you're in) How do you deal with cold weather when you're repointing? "We set up a climate-controlled environment in which we do the repointing and in which the mortar is allowed to cure." Frost and cold weather can damage your mortar before it even has a chance to cure. If they're working in cold weather, they should mask off the structure with a tarp, bring in a heater to keep the temperature at a reasonable level, and make sure that, after the repointing is finished, they keep the mortar protected from frost and cold until it is fully cured. Even then, I'd recommend easing the mortar back into fully cold temps by turning the heat down slightly every few hours, and so on.

This is just a little bit of info to get you started. Obviously, you can't know everything or you'd be a contractor yourself. But educate yourself a bit, and make sure to really scrutinize potential contractors. Chances are, if you get folks who are using lime-based mortar, and who know how to properly prepare your foundation joints for their new mortar, you've got someone who can probably do a decent enough job for you.

The National Park Service also has a great technical brief on the care and repair of historic masonry--I can't find my link but if you go to nps.gov and poke around you'll find it.

    Bookmark   October 12, 2006 at 9:49AM
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i see this message is kinda old but check out my web sight.
i specialize in original limestone restoration [ grapevineing] is what its called that the original look back in the 1900's any questions feel free to call.

thank you Rich H

Here is a link that might be useful: http://limestonefoundations.com

    Bookmark   July 28, 2010 at 9:28PM
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Why the heck did they use limestone as a foundation stone back then anyways...It's on our old house. I don't get it. Limestone erodes fast sometimes it's not exactly a solid material for building with. What was the reasoning?

    Bookmark   July 29, 2010 at 2:31AM
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