Mortar Type for Old Stone Foundation
Hi – I’m new to the forum and need some advice on how to repoint the stone foundation on my approximately 100 year old Victorian style house. I’m talking about repointing from the inside of the basement not the outside. The problem is that the old mortar is crumbling and falling out. If I use some type of tool (e.g., a long screwdriver) to scrap out the loose mortar how far in should I go and what type of mortar should I use? What is the best way to get the new mortar in? Obviously, I have no idea what was originally used or how important it is that any new mortar be compatible with the old. Do I need to use some type of waterprooofing mortar? Any advice or tips on actually caring out the job would also be appreciated. Thanks for the help.
Chuck
Replies
I buy bagged modern mortar for that same purpose. I have a fieldstone foundation. I think conventional mortar will be functional longer and easier to use than the old lime mortar.
Scrape out a bit of a cavity. Point with the mortar. That will seal the old lime mortar and keep it from further disappearing.
It's been a while with no reply, so my relatively unknowledgable reply will serve to keep your question fresh for others to see and respond. To my way of thinking, with stone, the hardness of the mortar shouldn't be an issue--I know that old brickwork can be harmed if repointed with hard mortar that has less lime than the old stuff, but stone should be okay with just about anything. I've even seen cement used (even with brick, but that's not a good idea). I'd think puttting in as deep as possible would be best--maybe even use one of those squeeze bags. Once the mortar's in, push it in with a repointing tool or just about anything that will fit. There are mortars modified with acrylic and latex and even, I think, epoxy. One of those sounds like it would be more flexible, adhere better and last longer than just regular mortar. But wait and see what the people who have more experience say.
what i'd guess you have is a lime mortar... basicly lime & sand... has about a 250psi and yes over time it turns to dust...
since you are inside and it won't freeze and at the most you'll only be in the house for another 30-80 years I'd use a type 1 white portland 1 part lime 1 part very fine white golf course sand 2 parts... add a little dish soap and some (very little grey portland if you need to kill the white some).... i'd try to get at least 1 inch deep (clean'n out the old soft stuff) and use'n a grout bag and and the mix a little on the wet side... just squeeze it in and wait til it sets and strike it off... you will be amazed how much material (mortar) this will eat up...
pony
Thanks for the response, you've peaked my interest with the dish soap - what is it for? How much working time do you have with the mortar once it is mixed. I'll have to try to figure out how much of a wall section I can effectively work with. Thanks again.
Chuck
the dish soap seems to help it "slide/squirt" out of the grout bag... you can trim the end of the grout bag to get the size/amount of mortar you want come'n out... but work'n with it all day the soap will make your arms/hands a little less tired...
we usually mix 1- 5gal bucket of portland 1-5gal bucket of lime 2-3 5 gal buckets of sand depending on how fine the sand is... if you get large sand or any rocks it really clogs up ur bags and wastes alot of time.... to this mix to knock the bright white out we add about a coffee cup of grey portland... and maybe 4 oz of dishsoap dollar store brand is fine... i use a "half bag mixer" for this mix and thats about full for it... (you can make 5gal bucket fulls with a big drill and mixer...) with this much lime in the mix you can re-wet it ....if it becomes stiff with no ill effect.... if your joints are clean and your gaps (joints) are large you sometimes want to fill em in 2 steps ... one person should be able to use up this amount in 2 hrs or so... stop'n joint your fills... after i joint i use a cheap $1 broom to come back a "sweep" the joints makes it look like it's "been there" and cleans em up pretty good too...
i fill my grout bag by step'n on the tip to close it... one hand hold'n the bag open while i use my trowl to fill the bag... about 5-7lbs best to refill a light bag alot vs try'n to hold up a 20lb one all day
pony
Pony: What kind of coffee cup? Dunkin'Donuts? He! He! He!Don, of D Mix infamyThe GlassMasterworks - If it scratches, I etch it!
You're going to get some varied answers to this question. I just dealt with the same issue in the spring.
It's lime mortar you've got there, and for repointing, the mixture I used (after asking LOTs of knowledgable folks) is 6-2-1:Sand-Lime-Portland. If asthetics are an issue, you'll want to use a sand that's as course (or fine) as what you have in there.
I found the mix above dries to a fairly light gray (I went a little heavier on the lime) when using a standard Portland. I might try that earlier suggestion of using white with a touch of grey this spring, though.
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As you indicated the answers are varying. What was the working time for the mix (6-2-1) that you used. Thanks.
Chuck
I mixed in small batches. Literally 6 shovels of sand, 2 lime... so I never hit the hard end of the working life of the mortar. I mixed it fairly stiff, but workable. Based on my experience on a cool day, and indoors... it was probably about 40-60 minutes... maybe longer. I've always been taught never to add water to mortar after it's mixed, so I'll remix a new batch rather than use stiffening mud._____________________________HomeBase______________ LLC
if it was "regular" mortar or concrete you really wouldn't want to "re-wet it" but with a high volume of lime it really isn't an issue since the stuff you are replace'n was 250psi max ... in the old days when it was strictly lime & no portland you could keep the lime mix for weeks since it really was a dry'n effect that made it turn hard... vs a chemical reaction of the portland... with the high percentage of lime I have never had a problem remix'n it... i hate waste'n anything... but i will save the really large cracks or voids for when the mortar sets some and hand pack em with the stiff mix... oh yeah wash your hands often if ur not use'n gloves (use gloves if you can) the lime is hard on your skin & open wounds
pony
I get my lime from farm supply stores or co-ops in 50lb bags for about half the price they charge at the brick place... just in case that helps...
If it was me.....I'd try and get all the loose stuff with the screwdriver, being careful not to dig and make loose any more stuff than necessary, by that I mean don't try and make anymore loose than already is....then use a grout bag (about 4 bucks) from HD or Lowes..it'll get it back in the cracks farther than trying to "tuck" it in and should be easier and faster, even with constant refilling of the grout bag.....then follow up a few minutes after pushing it in with the tucking procedure.....
If you aren't one of the one's I'm talking about,you shouldn't have any complaints....