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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  • Lots of interesting ideas.  Typically in the North East we would have just skinned stone on a masonry wall. You could mortar the joints. Obviously you could seal it an close it.  I would seal it with open cell spray foam, Keep the permeability between 3 and 10 perm.  Then air space and interior surface, like green board on steel or timber studs.

    I hate to cover it.  The answer for the 100 year old stone foundation in a cheap farm house would be drylock on well prepared surface.

    I liked the suggestion to look elsewhere.  You know where the air is coming in, so try to stop the air getting out.  Also, put some nice french doors inside these doors to separate this space from the rest of the house.  Obviously large open vertical columns of air, create their own motivating pressure.  But if you can seal the top, it will slow the infiltration in the bottom. 

  • I've drilled wood window and door jambs on double wythe brick walls and then dense packed.  Helped a lot.  Dunno if that applies to your job.

  • Air sealing a wall like this must be done with a vapor diffusive material or you will get spalled stone faces from sealing materials holding water. I recommend mixing hydrated lime with local clay soils, this is the way they have been sealed for millenia. Vapor open and beautiful. Do not use cement based products to fill the gaps as these are not vapor diffusive.

  • 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:



      • Try log cabin chinking.

  • 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. 

  • 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.
  • 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?

  • 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

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