Retrofit foam adhesive masonry veneer ties

[shobroco]

I read an earlier thread in which Ron stated that he has used expanding foam adhesive to tie masonry veneer to its back-up when the original ties had failed. I have never heard of this before and had the same initial reaction as hokie66, but I am interested in learning more. I frequently deal with heritage masonry buildings that require remediation of the ties between inner & outer wythes & we usually use drilled-in helical anchors. Stone walls with failed inner cores are usually grouted, but the possibility of using foam in them offers the added benefit of insulation. I am looking at an 1830s building with this problem right now. Has anyone ever done this?

 

[concretemasonry]

Putting something in the cavity between the back-up and the veneer can severely compromise the life of the wall and increase the possibility of water penetration.

If it is a wall intended to be be a multi-wythe bonded wall instead of a veneer, that is a totally different situation.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[shobroco]

This is an excerpt from the previous thread that explains his application a bit better, but I'm wondering about replacing grout with foam.

Ron (Structural) 13 Jul 10 17:55
I have used expanding foam adhesive for similar application of a historical building of about the same era. Works fine, you just have to be careful to control the foam's volumetric expansion so that you don't blow the bricks off the wall.



hokie66 (Structural) 16 Jul 10 22:58
I have used the screened adhesive anchors for brick veneer, and think it should work for stone. I don't like Ron's idea of filling the cavity with foam, but he generally has good reasons for his suggestions.



Ron (Structural) 17 Jul 10 16:10
hokie66...the cavity is not filled. The foam is injected in dollops at about the same spacing as you would normally have wall ties. The locations are offset so as not to impede drainage or air flow.

 

[Ron]

shobroco...

I'm a bit confused by this comment...

I'm wondering about replacing grout with foam.

The foam does not replace grout or mortar. It adheres the back side of the brick to the face of the substrate, assuming the substrate is something amenable to an adhesive, such as masonry, cast in place concrete, or in older buildings, structural clay tile.

As noted in the other thread, it is placed in dollops of about 6 inches in diameter, a little more perhaps, but not much less. Insertion points are typically through holes drilled in the mortar joints, preferably at an intersection between the vertical and horizontal joints.

Try a small area on the building. Play with the expansion rates and application rates. We did our mock-up testing on brick against concrete, in an effort to keep from pushing the brick out from the wall.

This method is being proposed on an existing building at a local university. The building is less than 10 years old, is 5 stories of brick veneer over masonry and cast-in-place concrete. I will post if I hear on the acceptance of the method.

Good luck.

 

[shobroco]

Ron:

Yes, I understand how you are using it but I am wondering if it could be used in a stone masonry wall that was built with inner and outer faces of dressed stone and a rubble core. This is a common 19th century wall and the core is frequently full of voids after a century or 2 of the poor lime mortar leaching away. We usually grout the core with low-pressure, low-strength grout injected through ports in the mortar joints to consolidate the core and rebond it to the faces. If low-expansion foam were used instead, it could do the same job as well as adding some insulation value, but I have never heard of anyone trying it. What do you think?

 

[Ron]

Not sure of the extent of your grout replacement, but keep in mind that foam is not a replacement for grout. Its properties are primarily in tensile and shear adhesion...not compression.

 

[dik]

... and bonding to rubble may be a bit of a challenge

Dik

 

[Ron]

Good point, dik!

 

[dik]

Ron:

I assume the expanding foam adhesive is a urethane product; do you have a particular product that you have used. I've not used method this but have heard of it being used.

I know about the rubble problems; many old timberframed barns have rubble filled walls and have reinforced a few...

Dik

 

[Ron]

dik...I believe the one we tested was "Polyfoam". Yes, it is a urethane material. I'll see if I can dig up the old report and see what we did.

Ron

 

[shobroco]

My shoring will be completed on Monday for a partially bulged and failing coursed stone wall 32' high on an 1834 house. We will then remove some of the failing face wythe (assuming it is a wythe & the wall has not been built as a 24" thick monolith) and see what the core looks like. If it looks possible to do some bonding with foam, you'll hear about it. Bonding foam to rubble would depend mainly on how clean it is; the shape of the cavities and the masonry units make foam more likely to fill & bond than any other material. At this point our intent is to rebuild the deformed area & stabilize/strengthen the rest. Of course the deformed area has 20' of wall above it just to make it interesting.

 

[Ron]

shobroco...thanks for the follow-up...let us know how it goes.

Ron

 

[shobroco]

This is the building, and the wall; not exactly one I want to screw up. The failing section is just out of sight at the end of the arrow.

 

[Ron]

shobroco...here's another shot of the building...I believe this is the wall to which you referred.

Most likely multiple wythe. Any consideration to using vacuum extraction to remove debris/rubble?

 

[shobroco]

The wall started to fail at the southwest (left in your photo) corner from about the main floor window sills down, with the biggest displacement of about 6-8" laterally at the height of the belt course. You can see the tie rods, I don't know when they were put in, but there have been historic problems. 2 or 3 years ago horizontal timbers were bolted through the wall to sandwich it & hold it in place. That's how it was when I first saw it (see attached photos) and it is too far gone in this immediate area to stay in place. We only want to rebuild the minimum necessary for structural stability since it is a national historic site & disturbing original fabric is to be restricted as much as possible. I'll update as we go.

 

[shobroco]

I attached 2 photos, only one showed up. Here is the other.

 

[Ron]

Yep! You gotta problem!

From the small reconstruction area, you can probably determine how best to proceed with the remainder of the rework.

I'm not sure of the thickness of the exterior veneer, but if it is more than 4 or 5 inches, I wouldn't consider the foam to be viable without some supplementary tie backs as well.

 

[dik]

Thanks for the photos and you have an interesting project ahead...

You may have difficulty with the urethane type of adhesive. It may tend to creep; you have a slight curvature to the wall with an outward compression component. YOu may want to look into stainless steel spiral ties. They may perform better under tension.

The alternative of removing the curvature from the wall is fraught with difficulty. The wall will act as a 'Jack' arch if you try to compress it inwards. Incredible forces will be required.

It may be possible to provide a temporary support for the upper portion and reconstruct the curved part. This is very expensive and great care must be exercised. It is also the most 'correct' way to restore it.

Care must be chosen in repair mortars notwithstanding the manner of repair, and a detailed analysis of existing mortar *must* be undertaken and a new similar mortar batched. There are specialist Architects and Engineers that you may want to consult with and the US Parks Board has specialists in historic restoration.

Dik

 

[dik]

Forgot to add:

Have you determined why the wall has bowed outwards?

As the curvature increases, so does the force tending to push it outwards (trivial comment).

Dik

 

[shobroco]

Ron:

I was initially looking at partial rebuilding along with grout and helical ties when I saw your previous thread about foam, which led me off on this path. I have dealt with historic buildings and masonry for a lot of years and never heard of the foam method before so I was curious. Believe me, it won't be used unless I think it will work and be appropriate and then I'd have to convince a few other people.

Dik: I have specified historic mortars for quite a few projects and am pretty familiar with them. This is about the 8th or 9th Canadian national historic site I've worked on. The wall is continuously supported now at the upper belt-course and I have movable shoring that is in shorter lengths and will be placed to allow removing the outer face in 5-6' widths down to grade as required. Once we remove the face we will see better why it has bulged out; the interior face is more or less where it started. The wall is really more like a set of piers: there are interior recesses so the thickness under the windows is only 8" & it is 24" beside the windows.