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HB's formula for a lime mortar mix for tuck pointing

Tue Apr 25, 2006 10:18 pm

Help! I have an old stone home built in 1864. I wanted to fix the place up but noticed that I can see daylight around the window frame in the attic. Should I get it repointed first or can I do the window repair and then repoint. I am concerned that the stones might give way during the repair process.

Wed Apr 26, 2006 8:44 am

It's kind of a tricky proposition with these old stone houses. What I've found is that the stones generally are locked into place and can't move too much, even if there's pointing missing. The old stone masons generally didn't allow the header of the windows and doors carry much weight either since they knew the wood headers weren't going to support all that weight for long without serious deflection. In a lot of areas you'll find that the stones over a door or window are wedge shaped and laid in such a way that they are forced together by the pull of gravity. It's usually not a full blown arch with a keystone, but if you look carefully you'll see a pattern.

That being said, I'm chicken and I would first repoint the area to give it some additional strength.

Here's my repointing recipe that seems to work.

Type "S" dry hydrated lime - (White powder)
Playbox sand, or any relatively fine sand with sharp edges. (Not river sand)

Mix the lime with water until you have a consistency something between cream cheese and sour cream. I use a drill (GOOD STRONG DRILL)with a paddle attachment and do the mixing in a 5 gallon pail. Just add a little of each into the bucket as you go. WEAR GOGGLES AND GLOVES. It's bad for your eyes and it'll give you the worst dishpan hands ever if you have too much skin contact with the lime.

I would make up about half a bucket to start. Once you've reached the right consistency, smooth out the putty in the bucket to make it level and then pour just a little water over it to cover it. (1/2 to 1/4 inch)

Put a lid on the bucket and let it sit for at least a week.

After the lime putty has aged for a week, you can mix it with sand to prepare your pointing mixture.

First pour off the water from the bucket of putty into a spray bottle. You'll nees this to wet the surface you're pointing. The lime in this water helps the mortar stick to the stone.

The recipe that I use is 2.5 parts sand to 1 part Putty (by volume) I use a coffee can and spatula to measure the stuff out.

Dumpe that stuf into a mortar pan or dishpan or something like that and then mix it up using a garden hoe. It should wind up the consistency of cookie dough. It's hard work and it will seem like your not getting anywhere for a while and then suddenly things will look a whole lot better.

The key thing is that the more you work it, the better it will be. It's one of the strange properties of a lime putty based mortar.

Now, vacuum out any loose stuff from the gaps that you're pointing, and physically knock out all mortar to a depth of about 1 inch from the face of the stone. Then spray the areea thouroughly with your lime water and start packing the mortar in place using a tool or your fingers, whatever. Try not to make layers more than one inch thick cause it will take a long time to dry. Make sure you pack it as deeply into the crevices betweeen the stones as possible.

When you're done, any leftover mortar and putty that you ahve mixed up can be stored indefinitely as long as you keep it from exposure to air. I seal mine up in a five gallon pail with a wet rag laying on the putty or mortar and the lid sealed on the bucket.

Keep in mind that the color of the mortar will depend on the sand you use. You can probably also get some tinting colors at the masonary supply store.

It's been my experience that Lowes or Home depot have nice 5 gallon pails, but that neither in my area carry the lime. Look in the yellow pages under masonary supplies for a supplier.

Good Luck - post back with any questions.

HB - lime geek in his spare time.

Wed Apr 26, 2006 9:55 am

Thank God for geeks.

Wed Apr 26, 2006 11:37 am

Does your lime puttyformula work for old brick? I need to do a fair amount of repointing on the foundation of my home.
PS I lived in Neffs, PA for abut 5 years, 11 years ago.

Wed Apr 26, 2006 2:12 pm

It should work for brick, but I don't know for sure.

I DO know that it's softer than the brick, so it should act properly and be the sacrificial part of the wall instead of the brick itself.

I also know that it's vapor permeable, so it won't keep moisture in the wall like a cement based mortar would.

At some point this summer I plan to lay up a brick foundation for a chicken coop and this is the recipe that I planned to use, but I do a lot of my learning through trial and error.

HB - best advice his father ever gave him was "Son, the lord hates a coward....go ahead give it a try, if we have to, we'll just do it again."

Wed Apr 26, 2006 7:58 pm

HB, great info. Lime putty is something I need to learn more about.

Will the lime water stain the stone, or, is it easily brushed off when dry?


Wed Apr 26, 2006 11:45 pm

Thanks HB, wanna help? You're not to far from me, Allentown PA. I will have to check back once I try this. I would like to at least try and then if I can't? Who ya gonna call! I will probably have to get a pro. I figured I could at least do the bottom 5 feet and then get my kid or someone taller to work their way up the wall. How about spiderman? Anyway thanks for the tip and I'll let you know how it works out.


By the way dennis I read that the residue is easily brushed off with a stiff nylon brush and not use metal on stone.

Thu Apr 27, 2006 6:44 am

I think that you're supposed to start at the top and work your way down. That way, if there's a rain storm, the water doesn't get into the wall and sit on top of your new pointing.

And don't get over aggressive when raking the old stuff out of the joints either. 1 inch into the joint is PLENTY from what I've read.

As far as the lime water staining the stone, I don't think it'll be that much an issue. But you'll want to protect the new pointing from the weather until it sets up properly. Best way to do this is to hang a canvas tarp over the area. You should spray down the canvas with water to keep the whole area damp so that the pointing doesn't dry out too quickly and crack.

As for a pro to do teh work, there's a fellow in Quakertown or Doylestown by the name of Degruchy. He is a mason that deals entirely inhistoric homes. From what I've heard he's very good. I doubt he'd agree with my recipe since he likes to use actual quick lime instead of the dry hydrated stuff, but there's two different schools of thought out there regarding that issue - besides, I can't for the life of me find the quicklime anywhere. :roll:

Good Luck!

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