# gaps in masonry foundation, expanding foam or mortar



## LMHmedchem

I am currently working on my basement and am in the middle of  re-pointing my the 120 year old granite foundation. Much of the mortar  has turned into something that looks like plaster dust, so I am removing  and replacing it. After removing some of the old mortar, there are some  large gaps inside between the blocks, like that I can put my arm into. I  guess they didn't do much dressing of the blocks on site but just  stacked them up and mortared them into place. I have used some great  stuff to fill some of the gaps, but I think I need a much larger volume  product if I'm going to fill all of them.

There has never been any issue with water in the basement, and some of the gaps are obviously continuous to the outside, so the drainage must be good enough to prevent leaks. Even so, I think  it is a good idea to fill these gaps since I have it all open. It will  also be allot easier to re-point if the bigger gaps have been reduced  considerably.

I have added some pictures below.

The first picture is a section of the wall I am working on. All the the loose mortar has been removed.

The second picture is of a common gap I am seeing. This vertical gap  runs for about 2 feet and is about 1-3 inches wide and about 1 foot  deep.

The third picture is of a horizontal gap that is 1 foot deep 18 inches  wide and about 5 inches tall. There are two loose pieces of granite  sitting at the front of the gap. In the last picture, I have removed the  loose pieces and you can see all the way into the gap.

There are two places where there is an ~8x8 inch gap that runs all the  way through. I can see the underground dirt on the other side. I have no  idea why there isn't water coming in here, but there is a cantilevered  section of the house over that area and the grade slopes away from the  house pretty well. I guess the overhand is keeping it dry enough to keep  the water out. There are some signs of moisture in this area though,  but nothing like standing water.

I found this video
[ame]http://www.veoh.com/watch/v17334188sxcp6K25[/ame]

by a group near here called the mended wall. They do allot of  conservation/restoration of homes much older than mine. The video shows  Andrew doing most of the same things I have been doing, removing loose  mortar and stone, using a vacuum to remove dirt and debris, etc. He just  filled all the gaps with a mixture of sand mix and type N lime. He  didn't specify the proportions, so I'm not sure where to go with that.  These are also restorations that aim to preserve the historical  significance of the home and I don't know if that affects the techniques I would want or not.

This article,
http://voices.yahoo.com/adding-struc...558.html?cat=6

advised what I was thinking about, which is to inject closed cell  expanding foam into the gaps, which would be much quicker. The article  didn't specify the type of foam to use or where to get it.

I have also thought of just shoveling concrete into the large areas to  fill as much as possible and then using standard mortar mix to finish  the pointing, or using cement to fill as much as possible, adding an  inch or two of spray foam to seal and insulate, and then pointing. One  of the problems is that some of the gaps have narrow openings, but get  fairly large as they go back. It would be pretty difficult go get any  kind of mortar back in there without some kind of pump. I also know  there are other expanding hydraulic cement like products that are used  for filling and sealing applications.

I don't really know if this wall need structural reinforcement or not.  It has been where it is for more than 120 years with no shifting, so I  suspect that it does not need much more than would be provided by  replacing the loose rock and re-pointing enough to fill the gaps. Adding  additional structure isn't going to do any harm however, and it would  be nice if this remained stable for another 120 years.

There are allot of possibilities and I am a bit in the weeds here, so I would really appreciate any suggestions.

This site seems to have a reasonable selection of expanding foam,
http://www.energyefficientsolutions....amproducts.asp

If I do use foam, I'm not really sure what to get, 1-component, 2-component, fire block, etc. I'm not sure which of these would qualify as "structural". The products at this site range in price from $90-$800 and I don't want to spend allot   here unless it is really necessary. It is hard to tell how large the   largest gaps are, but I can always make repeat applications if   necessary. Most of these things are advertised as waterproof, but I   don't really know what that means in practice.

I'm not really sure what to get, or where to get it, so suggestions   would be appreciated. Is there a standard for this sort of application?

Thanks, 

*LMHmedchem

*


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## BridgeMan

I wouldn't use any type of spray foam to fill those gaps.  Won't properly seal when the time comes, and certainly provides no structural strength.  Stick with mortar, and maybe consider Type S if you want it to be stronger.


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## LMHmedchem

BridgeMan said:


> I wouldn't use any type of spray foam to fill those gaps.  Won't properly seal when the time comes, and certainly provides no structural strength.  Stick with mortar, and maybe consider Type S if you want it to be stronger.


Is the use of type S going to present any problem in painting it (on the inside)? I guess I would have to let it cure and dry for at least a month before painting.

Is there some reason why I can't just fill the large gaps with concrete? I'm not completely sure on the difference, other than different proportions of sand, gravel, and Portland cement. I was thinking about spray foam because I don't think that these large gaps have even been filled with anything. The mortar was only about 1" deep and just held the small stones in place and sealed the gaps. I thing that there have always been large internal cavities. I thought that foam would be better than nothing and would provide a decent water tight seal. There are some foams that are considered "structural", but I don't really know what that means.

I can certainly fill everything up with mortar, but it will take longer. I'm also not sure what to do with the large gaps the have very narrow openings. I could always break out the diamond grinder and open the gaps some, but that is no fun. Also, how clean do I have to get the rock before re-applying mortar. Do I need to clean with water and detergent, or will just a dry brush be alright?

I have attached a picture of what this looks like on the outside. It's surprising how much cleaner it looks on the outside, thought I'm sure it was re-pointed at least once.

*LMHmedchem*


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## LMHmedchem

Well I guess I am going to be using type S mortar, since there have been no other suggestions. What is a good ratio to use? I would guess 1 part type S to 2-2.5 parts mason sand, but I could also see using sand mix instead of just sharp sand. If I use something like QUIKRETE type S Mason Mix, would I add anything or just use it straight?

Any suggestions on this?

*LMHmedchem*


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## mudmixer

Since you are trying to fill the voids and hopefully do some sealing foam is a wast of time.

Use mortar or masonry grout to fill the voids. Obviously concrete will not work. A wet, soupy grout (Portland cement and sand) would be best if you can contain it  since it will fill all voids.  A second choice would to use a lower strength wet mortar that you can force into the voids and keep it there. It will seal somewhat and provide great stability and work well since you do not have a leakage problem, any minor shrinkage would not be a problem. As in all masonry, you use the lowest strength mortar possible (Type N), since mortar strength is really immaterial, especially with you situation.

Type N masonry cement is not as readily available as Type N premixed mortar, so you could use either Type S cement or just  Portland and sand, depending on your learned skills.

Dick


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## LMHmedchem

mudmixer said:


> Since you are trying to fill the voids and hopefully do some sealing foam is a wast of time.
> 
> Use mortar or masonry grout to fill the voids. Obviously concrete will not work. A wet, soupy grout (Portland cement and sand) would be best if you can contain it since it will fill all voids. A second choice would to use a lower strength wet mortar that you can force into the voids and keep it there. It will seal somewhat and provide great stability and work well since you do not have a leakage problem, any minor shrinkage would not be a problem. As in all masonry, you use the lowest strength mortar possible (Type N), since mortar strength is really immaterial, especially with you situation.
> 
> Type N masonry cement is not as readily available as Type N premixed mortar, so you could use either Type S cement or just Portland and sand, depending on your learned skills.
> 
> Dick


I started using type S because this is below grade, but that is just a guess. The easiest thing for me to get was the QUIKRETE type S Mason Mix. I also have Portland around and sand. I have been basically skim coating the old "moon surface" concrete floor with a 2-1 mix of Portland and play sand. I have mixed it to the consistency of drywall mud and applied it more or less the same way, pre-treating the old concrete with concrete adhesive. The results have been very good so far, but I am only able to so small sections at a time.

If I can buy straight type S cement, what ratio would I use with the masons sand (I wouldn't use play sand here)? What is the difference between type S cement and portland? I was trying to avoid getting into the more complex mixtures of cement, lime, and sand, even though that was traditional. I'm not sure what the difference is between these mortar mixes and cement. I have always just thought there were different ratios of ingredients.

I did another part of this earlier, but it was in much better shape so I didn't have to remove as much of the old mortar. I did use some spray foam to fill some of of the cavities that I couldn't get to. I believe that these cavities have always been there (empty), so I thought that adding some insulation couldn't do any harm. This part of the foundation has an edition with a full basement on the other side, so it's not exposed to whether any more. I just used bagged mortar mix to re-point where the mortar was loose or missing. That part turned out really well, at least it looks good. I am going to be painting this in the end. I probably would have done the same here, but this part is in bad shape and needs a much more complete treatment. It was behind the oil tank at one point and I think the rest got redone, and this wasn't.

At this point, I have 4 bags of QUIKRETE type S Mason Mix and 1.5 bags of Portland. I can get pretty much anything else if I am going in the wrong direction here. I guess I will be skipping the expanding foam, but that would have been really fast compared to using mortar. Fast isn't that helpful if it's the wrong method I guess.

I do have a grout bag that I could use to get a wet mix back into some of the places that have large cavities with narrow openings. Would there be a problem using more than one thing in combination, since I probably won't be able to fill all the voids with a single solution?

This stone is granite in case I didn't mention that at some point. I know that sometimes the material has an impact on the kind of mortar to use.

*LMHmedchem*


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## LMHmedchem

mudmixer said:


> Since you are trying to fill the voids and hopefully do some sealing foam is a wast of time.
> 
> Use mortar or masonry grout to fill the voids. Obviously concrete will  not work. A wet, soupy grout (Portland cement and sand) would be best if  you can contain it  since it will fill all voids.  A second choice  would to use a lower strength wet mortar that you can force into the  voids and keep it there. It will seal somewhat and provide great  stability and work well since you do not have a leakage problem, any  minor shrinkage would not be a problem. As in all masonry, you use the  lowest strength mortar possible (Type N), since mortar strength is  really immaterial, especially with you situation.
> 
> Type N masonry cement is not as readily available as Type N premixed  mortar, so you could use either Type S cement or just  Portland and  sand, depending on your learned skills.
> 
> Dick


Well I am moving along a bit, mostly trying to get the  technique right. I have been filling up the outside joints with the  smaller pieces of granite that I removed with the old mortar and filling  about 3 inched in with mortar. I am using the quickerete type S mason  mix. After that sets up, I have a well behind it that is contained by  the new mortar. I have been using the same mix, but making it wetter,  about twice at thick as paint. Then I have just poured that into the  open well behind the replace mortar. Some of the voids lower down are  large and I have poured many gallons of this mix into some of them.  Eventually they fill up and top off the well. Even though the mix is so  wet, it seems to set up reasonably well just overnight. I am working  along the wall, starting at the bottom. By the time I have gone all the  way across, the wet mix will have had several days to set up and I will repeat for the next level up.

I am planning on painting the wall, but with all the water in this mix I  guess I would want to wait at least 2 months or so before doing that.

It would be helpful to know if I am in the process of turning my foundation into the Okefenokee Swamp, so I would really appreciate it if someone would let me know if they think I am.

I will try to put up some more pictures for the next round of filling I do.

*LMHmedchem*


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## NickS

LMHmedchem,

Hi, I found your posting in my search to address exactly the issues/questions that you describe.  I have a granite foundation (house built in 1835), where I need to fill lots voids behind the first layer of granite, followed by pointing, and wondered about using foam for the voids.  This thread has been quite helpful, particularly the conclusion about using a wet-soupy mix of type S mason mix, poured into the voids.  I'm wondering now, seven years later, how this has worked out for you?  Seems like the perfect solution to my problem, as injecting foam into the voids just doesn't sound that effective (as discussed in this thread).    I suspect I will also require gallons of mix to fill the voids in my wall.


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