Glass Brick in CMU Wall? 1

[ChorasDen]

Greetings,

Performed a home inspection several days ago (home was built around 1960) where the first floor walls were constructed with CMU brick with glass bricks framed within this wall to provide light into the first floor. This wall supports a 2-story gabled end roof, with the second floor joists running perpendicular to this wall. I've never dealt with glass brick like this before (in one of the photos, you can see one side of the glass is broken, and the interior is hollow), does anyone know who may have manufactured these, or what loads they can resist?

 

[SwinnyGG]

Pittsburgh Corning is, to my knowledge, the only manufacturer of glass block in the US. PC specifically states in their literature that their products are not for load-bearing assemblies. As such, they provide no structural ratings at all (and in the past, when I've asked, they will refuse to provide them) beyond a maximum panel height for each type. For standard 4" glass block, which that appears to be, max panel height is 20 feet I think.

That looks an awful lot like a CIP basement wall with a cast opening which was then infilled with CMU. Are you certain there isn't a header above that opening, buried in the wall?

 

[ChorasDen]

Thanks Swinny, that helps a lot.

I agree about the CIP walls with the infill.

I am certain a header is not installed overtop. the floor framing is rough sawn 2x8 that bears onto the double top plate overtop the glass block. There is rough sawn 2x8 rim behind supporting the wall above, without hangers, see attached images. The double top plate concerns with tension perp is another discussion that I'll address later, but I was mostly curious about the glass.

 

[structSU10]

There may be a rim board behind the joist that spans over the glass block. It would likely take a pretty decent member to do that though.

 

[IRstuff]

Are the exposed studs in the first photo original or something new? They look ad hoc, since it looks like the ceiling drywall is interposed between the top plate over studs and joist in the ceiling in the 4th photo.

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[SwinnyGG]

I think 'ad hoc' is a good description for most all the sh*t in those photos.

 

[ChorasDen]

They are relatively new. Currently have an electric water heater in this closet area. Previous owner used this area as a bedroom, likely wanted separation in the room from the water heater and electrical panel. This partition wall was dry walled just prior to my visit.

Previous owner also installed double layer gyp below the floor joists, which I found very interesting.

 

[XR250]

Any header would have to have basically zero deflection unless a gap exists.
As such they are likely acting as load bearing elements. They probably have a fair amount of capacity - even though they are not rated.

 

[hokie66]

Glass block should be treated like any other window, just as an opening in a structural wall.

 

[MIStructE_IRE]

The dogs dinner you see in those photos is all too common and the main reason I don’t do residential inspections anymore.

 

[dhengr]

ChorasDen:
Alternatively, that glass block has apparently been there and performed pretty well for about 60 years, so what’s the question? The broken glass block is in a fairly precarious position and was probably hit by a snow shovel, heavy object being moved up the conc. steps, or some such. A good mason can replace that broken glass block. It is a bit of a cobbled detail, but you aren’t required to fix the world, when it ain’t broke. Why not study the entire wall detail in that area and come up with a reasonable explanation of why it has worked all these years, and then leave it alone, as there is (if there is) no indication that it is a structural issue. If the ext. conc. slab has a good slope and caulking at the wall, that helps keep the wall dry. That looks like a fairly protected wall area from above, in the ext. photos. Although, the int. photos may show a little water intrusion, at the bot. of the window, over the years. Do a detailed and complete cross section through that wall and the glass block. There are likely several sill pls./header pls. above the glass block, the 2nd. fl. joists framing onto them, a rim jst. (maybe a couple) over the 8’-8” window opening, and the 2nd fl. wall framing above the fl. framing platform. Is there any indication of vert. movement of the fl. jsts. (w.r.t. the rim joist) over the window, and indication that they are not being adequately supported. What’s the makeup of the upper wall, sheathing, etc., many times they will easily span that kind of opening, acting as a deep beam, a bit of a box beam, or a shear panel beam. The wall sheathing might be 1x6 ship lap which is not as strong as plywd. sheathing might be.

 

[ChorasDen]

dhengr - I agree about the continued performance of this wall since original construction. This post was really just a "What am I looking at here, and can this product be used as originally prescribed?" type of post. I had assumed this product was used outside the manufacturers guidelines, and further comments above have reinforced that idea.

I'd argue that it is a structural issue, however. This home is located in a high seismic area, and the brittle performance of this glass may cause further unexpected performance. (I might add there is little/no lateral detailing across the entire structure, so the glass is not the only area to be concerned for seismic performance).