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I need a good stone foundation ratio.

15K views 112 replies 18 participants last post by  Fancis Casini 
#1 ·
I got tasked with rebuilding a stacked stone foundation from an early 1800's house (I am going to be there forever).

Two walls caved in, so I excavated and tore down the walls, dug down to the cobble trench footer they made, leveled with crushed stone and started building again, but I need a decent mix design.

The Art of the Stone Mason says to use 1-1-7, I tried it out yesterday and it seems a little rich to me, what have you guys used with success on something like this.

Normally on patch jobs I just get bagged Type N, but it's not practical for such a large project.
 
#48 ·
If the stone is a granite or hard stone (not limestone or sandstone) a type S would be fine 1:2:9, lime:portland:sand. or use bagged type S.
I did a mix similar to that but a touch more lime because the bulk of the foundation was a limestone and some serpentine (I think it was anyway ).


For the types of stone that Sit has to work with, I think I would lean towards a softer mix.

Sit, I am familiar with that stone. I have a good friend that moved to Oxford,NY directly east of you and rt 81. He has the same two types of stone in his farmhouse and barn foundations. He also has miles of stonewalls with it too. All the foundations were older than 50 years and had a high lime content....they were in great shape the last time I was there. They weren't pretty either.:laughing:
 
#13 ·
It was raining (snowing actually) so I didn't get to play with any mixes, checking it this morning though I think I need to lean out the sand a little and replace some portland with a little lime.

I might try a small batch of 1/2 Portland 1.5 lime 6 sand, just to see what happens, to avoid giving my helper anything he can screw up though I might just switch over to 50:50 pre-bagged and go 2:6.

I haven't done much stacked stone other than repairs, so I am attempting to find something that won't be too rigid.

The guy doesn't want it dry stacked either, he wants it to match the other two walls (which have been lime puttied about 10 times by now)
 
#15 ·
It was raining (snowing actually) so I didn't get to play with any mixes, checking it this morning though I think I need to lean out the sand a little and replace some portland with a little lime.

I might try a small batch of 1/2 Portland 1.5 lime 6 sand, just to see what happens, to avoid giving my helper anything he can screw up though I might just switch over to 50:50 pre-bagged and go 2:6.

I haven't done much stacked stone other than repairs, so I am attempting to find something that won't be too rigid.
Sitdnwagon,try my mix,thats a bag of mortar,quarter bag of lime and 5 sand..try it I guarantee you ll like it.
 
#21 ·
I think thats the problem with talking about this online, even regionally we have our own terms for things.

By pre-bagged I mean pre-blended type N, portland and lime.

Brixment is what we have locally, makes a great brick mortar with the right sand, not sure how it will do for stone though.
 
#22 ·
I agree about the terminology. Preblended, yes. Carry on sir.

The only suggestion that I would give you is to mix it as dry as you can so long as it still can hold it's form. My test for re-pointing and stone mud is to make a ball and thow it about a foot in the air and catch it. It should crack but not crumble. You may think also of a slightly richer mix say an extra 1/4 type N or so. Just to ensure a real good bond.
 
#25 ·
For load baring stonework I would suggest portland cement with a 2 1/2 sand ratio. 3 buckets to half bag I'd say.. I use shovel amount and use a flat shovel for my measurements. Adding lime will weaken the mix, so bricky alchemy isn't necessary.
 
#26 ·
so you don't use any masonry cement in your mix at all? My mix was in buckets. and just to solve some basic math 5 shovels= 1 bucket 1 bag of portland cement=2 buckets 1 bag of masonry cement"mortar" is 1.75 buckets. that is with a 70lbs bag of mortar and a 90lb bag of portland. when we discuss sand it could be a whole other thread since we would have to break that down to seive anylisis but basicly mortar sand is fine and crete sand is fairly course with fewer fines.
 
#33 ·
I am calling out whoever makes wrist breaker portland mud and throws it out claiming it's unworkable. They have to be clueless when it comes to consistency. It's green for awhile so I'd say mortar flashes faster. The question would have been better if it was asking to add mortar to portland, if you were to recipe with a bag of portland, lime for instance, it would be at a 10-15% ratio off portland. If you can manage your own mud then no you could do your work solo but I can't blame the mud when someone isn't thorough. If you like to use mortar build with culture stone.
 
#35 ·
twice...TWICE did I try to use straight portland and sand...it was **** both times,no offence JD3lta(maybe it works for you).

First time I tried parging with that,it cracked a month later and I re-did it(was playing around on gf's dad's shed). Second time I installed cultured stone on same shed...wet stack...all joints cracked 2 weeks in.

never again.
 
#36 ·
The problem with mix designs and stonework I think is that we won't be around in 150 years to check on it, and by then another better product will probably come along.

The old timers used lime putty/sand mix, not because it is better or worse, but that is all they had for awhile.

I considered a straight portland mix, but was hoping the lime would give it a little softness to accommodate the stone shifting a little. Hard to explain in text, but like when you clean off old rocks, a portland mix will slide right off with a good tap, but you can really hammer on some types of lime mixes and only dent it and make little progress in actually removing it.
 
#38 ·
Right but we canb look back and see what HAS worked for the last centuries. I frequently see stone that has been repoinetd with a hard portland based mix 50, 30 even 20 years ago. Joints hanging tough and stone delaminating and crumblig. Area 3 feet away that wasn't touched is fine. See it all the time.

JD3 I think saying that people who like a workable mix should stick to cultured stone is rude and insulting. Mortar has been a part of masonry for almost it's entire history. In many walls it's 25% of the wall. The guy who dumped the mix works with natural stone day in and day out. He's barely 40 and has about 25 years experience. He can also pick up a wheelbarrow full of mud. No joke. If you want to tell him he's an idiot, I'll try to get you in touch
 
#41 ·
I'm not surprised that everybody has a somewhat different recipe, but I am surprised by how different some of these are.......honestly, if we could see all these next to each other, it's almost funny. I'm more of a NHL 3.5 to about 2 1/2 sharp sand for restoration work. One thing though; I have only heard of someone using a straight portland/sand mix.......what most masons call 'grout'..........I am curious as to what mix bytor uses........
 
#42 · (Edited)
We generally use something along the lines of a 1:1:6 portland/lime/sand. (resulting in a type 'n' mix)
But, that does vary... on our current granite random/rubbly ashlar chimney we are using 1:2.5 type 's' masonry cement/sand mix to lay up the stone and will most likely point with the 1:1:6.

Of course we're not working on an early 1800's house as the OP is... wouldn't that call for a straight lime mortar to match existing? I suppose if I were doing below grade stonework from scratch I would be more comfortable with a type 's' (1:2:9 mix).
 
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