HELP - AIR SEALING a Continuous Stone Interior/ Exterior Wall

I just recently audited a home that had a blower door number of 11,684 CFM50 and/or 11.81 ACH50. And of course one of the main air infiltration culprits was a stone face wall that was continuous on the outside and inside of the building envelope. The basics as I see it is this: the 1/4" stone joints allow air to freely flow into the house.

Does anyone know of any good methods to seal a high-end stone wall air leakage like this? 


Below are some photos:

PHOTO OF HOUSE Stone Wall Located Bottom Right

CLOSEUP PHOTO OF HOUSE Stone Wall / Back Exterior Door (OUTSIDE)

INFRARED/ ACTUAL Stone Wall/ Back Exterior Door (INSIDE)


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At first, I thought that maybe there would be a core wall of CMU, and thus possibly a way to reach the interior top of the wall to find a way to block airflow from passing over it, and eliminating at least part of the problem; maybe even filling the wall with a self leveling cementitous product that is thick enough to not pour out the joints; or possibly do so with a very fine dry sand. But apparently, the builder did go with the old-fashioned way of building a stone wall, with a skilled mason. Looks beautiful.

I would check with a masonry supply house to see what products or methods they have, but clearly there are air gaps in the grout material that will be impossible to specifically locate. Considering the appearance of the wall, I'm not sure I would trust someone to do a clean job using caulk or foam. Maybe use backer rod and stuff it into the joints? I'm not sure how effective it would be, but it's a fairly inexpensive material for a first attempt. 

Dry stacked or is there mortar holding it together? If there are actual mortar joints you can see about getting a mason in there to fix all the B-holes - if it is dry stack then they will not like the fix (and no it does not involve mortar or caulk) & just concentrating on fixing the soffit areas, recessed lights, etc...

While that is a lot of leakage, is it all coming from that wall surface alone?  Wall leakage is a big issue, but what if you concentrated on all the other leaks could you bring the exchanges down enough to warrant not having to do this part?

Only sealants I am aware of are for moisture and will not stop air flow transfer such as this. I would simply concentrate on the other leaks in the house assuming they have more and inform the owner that they will have to live with what is going on on that wall surface.

There is a web site where you can make an inquiry about this. It is the brick industry site.  Perhaps you will find the information your looking for there.

Good luck, keep us posted on how you make out with this one.

Maybe Zone Pressure Diagnostics could of been done to determine where the significant air leak spots are.  If dry stacked, air leakage could be more significant in walls than in attic.  

During the audit, I wonder if the walls felt very leaky.  If comfort is an issue, air sealing direct leakage to indoors is a high priority.  The Mean Radiant Temperature or the average radiant temperature of the room is significant to the comfort and if direct convective paths are present, the wind chill will significantly reduce effectiveness of thermal boundary or insulation if present.  

Hello.  I have a large basalt stone floor to vaulted ceiling tall fireplace that also leaks. I have reduced my ACH to 8 from 12 and am now working on the fireplace. My plan is to caulk/foam (may be more economical)  the whole dang thing from the attic/basement side first and see what that gets me.  Foam would be unsightly for you, I think, so clear caulk??

As an aside, based on your numbers, I calculated the the house in question to be about 2, 337 sq. ft. with a volume of 58,420 cu. ft.  Is this correct? I am far from an expert in this stuff but am trying to learn.  Thank you.  John


Is it possible to cover the wall adequately enough to isolate that air leakage? Even if you covered the wall exterior and interior with plastic sheeting, or covered the exterior, and built a plastic wall on the interior, you might be able to verify a quantity of air leakage from the wall. Given the pictures of the house, it looks custom built. Before you go intruding on the mortar joints, (or voids, if a dry laid wall), you might want to verify the wall is the biggest leakage site. If it is, try backer rod or injected foam from the outside into the joints, covered with a clear siliconized caulk, and recessed as much as reasonable. It may be quite a time consuming project, another reason to verify the culprit.

Finished Floor Area: 5,460 sf / 59,340 cf / 4 Stories / Half Slab - Half Crawlspace

Are you saying that there's not a block or poured concrete wall in the middle of all that stone? That's almost inconceivable to me in modern construction, but I suppose it's possible... in which case you would have to grout the entire thing, probably on all sides. I would call a commercial stone maintenance/restoration company if you have access to such a thing--those are the guys who know how to put mortars and sealants into gaps and make it look good.

If it's just the gaps between stones at places where door and window jambs are let in, then it's hard to see how it's responsible for all that leakage, although we can't see the extent of the stone in the few shots you posted. 

Question about your manometer setup. You appear to have your indoor references teed together and piped away from the manometer. What's the reason? And, you appear to have -43pa at ~5250 CFM, so how did you come up with the 11,000 number?

Thanks everyone for your input. The test was a two blower door test (that only got up to -43 Pa) - we had to add up both manometer readings and use the Can't Reach Fifty factor. The wall is a facade about 3" thick (with concrete masonry on ext. and wood insulated framing on int.) that is made to look like a dry stack wall - mortar is used in the back for stability. 

Below was a recommendation by another co-worker that I think I am leaning towards using:

Because the original construction process was mismanaged and the masons installed the rock prior to other finishes, your options are somewhat limited if you are to maintain the dry stack appearance.  I would recommend that you seek to limit the air leakage in the following manner.


  1. Obtain a piece of the mortar used to “seal” between the door and the rock.  This sample can be used to “color match” a terpolymer rubber adhesive/sealant such as Solar Seal #900.
  2. Drill 3/8” cores in each horizontal “mortar” joint ( I will call them mortar joints even though it is dry stacked) as close to the door jamb as possible.  The proximity of the hole to jamb will depend on the final finish used to bridge the jamb to rock transition which at present is the vertical mortar joint.
  3. Install the terpolymer rubber adhesive/sealant in each of these cores.  This will provide air sealing points at each of the major contributors at the most critical point.
  4. Final finish: Option 1) assess the color match and blending of the existing mortar and terpolymer rubber adhesive/sealant to determine if further finishing is required.  Option 2) Apply new mortar.  Option 3) Score rock 5/8” along door jamb into which a color matched Aluminum angle trim 1/2”x1/2” can be installed.  This angle transition can be adhered to the rock with the terpolymer rubber adhesive/sealant used in the cores.  It can be sealed to the door jamb with a color matching sealant.
  5. Repeat process for interior side of jamb.  May want to test progress of exterior prior to.
  6. Test with blower door and smoke pencil to assess improvement and locate problem areas.
  7. As to the soffit to rock transition.  I would recommend scribing the rock prior to removing the soffit.  Based on the thickness of the soffit and the amount of rock that protrudes there are a couple of options.  If the finished soffit material is thick enough, then a new piece which will extend beyond the rock can be planed and installed.  If the finished soffit material is not thick enough, then the rock can be cut to allow for the finsished soffit to extend beyond the rock.  If there is insufficient room to cut the rock, then it may be necessary to either remove the top row of rock to be reinstalled to fit under the finished soffit or consider continuing the Aluminum trim across the soffit behind which other potentially unsightly air sealing measures have been applied.

It looks to me like the main leakage is from the intersection of stone and conventional framing,  not necessarily directly through the wall. 


In the second picture, is the stone i see that appears to be interior actually a reflection?  I suspect it is.  in the shot with the recessed lights, I am looking in from outside too, right?  if so, does the stone wall pass through those features and continue inside?  If not, why not cut away the interior sheetrock finishes and approach the Butt end of the stone wall in the interstitial space with foam?  Do the same at the soffit.  Then do a blower door test and use smoke to identify any leaks you may have missed at these transitions that are ininterstitial space and seal those.  Then put the sheetrock back up and refinish it. 

I had a similar issue with an exposed historic brick wall in a condo I was testing. We couldn't find the leak with our eyes or thermal imaging becuase the leak was EVERYWHERE. We confirmed this when we taped a sheet of poly over the wall and when we kicked on the blower door, the poly ballooned like crazy at the slightest pressure change. The owner sealed every mortar joint with silicone caulk and then painted the wall (~20' x 10') with several gallons of a transparent sealer. The porous brick guzzled the paint like crazy. It was very important to the owner to have the urban loft feel of the exposed brick. Sealing just this one section of one of the four exposed walls reduced air infiltration from 14 ACH@50 to <7 ACH@50.

Hi Jonathan,

I have the same problem after the catastrophic result from Blower door test 30-35 ACH@50Pa of two stone built houses in mountain. I and my team developed air sealing technology for stone walls without mortar.

After the air sealing we achieved major success to reduce the Blower door test results more that 3 times!

Sorry for my poor english!

Here is some thermograms, videos and photos from this project:


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