Retrofit Lintel in CMU wall with Loose Fill Insulation

[Guastavino]

All,

So interesting problem here. A client wants to create a larger opening (existing 3'-0"x7'-0" door in 3'-4"x7'-4" masonry opening). They want to go to 5'x7' (5'-4"x7'-4" masonry opening), IE (2) 30" doors. It's a single wythe exterior 8" CMU wall with #6 bars at 48" o/c and (2) each side of opening (I bet they only installed one in the field, but the drawings called for (2-#6) each side of openings). Anyway, it also has LOOSE FILL insulation, (Fun times!) Wall is just painted on the exterior. Also, it is load bearing, but not much.

A few questions arise:

1. Typically, I like steel lintels for retrofit, but here I'm thinking a 16" deep bond beam with one more course toothed in. Anyone successfully tried this before? Channel above as "temporary shoring". Reason I'm thinking CMU lintel is the insulation issue.

2. I'm concerned that all the loose insulation is going to pour out of the wall during construction (after they take out the CMU to install the new lintel). Has anyone found a good way to prevent that?

3. I think this is an egress door, and I'm not sure that (2) 30" doors will cut it. I'm somewhat putting on my architect hat here, which I don't want to do, but I also want to advise the client that he needs to maintain egress requirements. There are only (2) exits (this is one of them) and I'm thinking you need (2) accessible for retail space (2009 IBC here), which I think means a 3'-0" door. Anyone dealt with this?

4. Lastly, I'm thinking "flashing". I've never been a big fan of block-filled and painted CMU as the only waterproofing, but it's done a lot around my parts. Especially if I go the steel route. Any ideas/thoughts?

I'm at the point where I may tell the client it's could be a bit more involved/expensive than he had hoped, because he was on a somewhat tight budget, albeit reasonable. Thanks to all!

 

[KootK]

If you're going with a new masonry lintel, I'm not sure that you need the temporary channels. You've got substantial contiguous block on all three sides. The mason can likely just remove the block in the load triangle above the new lintel and fill it back in once the new lintel is in place.

The core fill is a tough one. My gut tells me it wouldn't fall out but I've no anecdotal evidence to substantiate that. I suppose you could use HY70 screen tubes without the anchors to block off the cells but that seems like a lot of effort to go through to preserve insulation in an area where the door frame will be a pretty significant thermal break in its own right.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Guastavino]

Thanks KootK. I may make them drill a "pilot hole" and see how loose it all is. I've heard these things can leak out a lot, albeit I haven't seen it first hand.

 

[KootK]

Check this out: Link. Perhaps what is lost could be restored. Although I'm not sure how you'd go about establishing where voids had been created if some but not all of the insulation leaks out. Maybe you could pressure fill from the lintel up and from the deck down and call that good enough.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Confirmation of tendency to leak but perhaps hang up on page three: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

Maybe slide a piece of sheet metal in your saw cut before you remove the CMU to block off the insulation. Remove and point once the lintel is in.

 

[Guastavino]

So I think I'm going to do a 16" Bond beam and take out (3) courses of block. 16" bond beam because I don't trust the contractor to get the grouting/consolidation right on such a shallow grout placement in tight quarters. Then, if all the insulation falls out, they can inject new foam insulation back in.

As for the door, I'm just planning to advise the client to look into with an Architect as needed.

 

[BAretired]

I believe the loose fill will leak out if you don't plug the cells of the block. One idea which may work is to break out the face shell, then shove crumpled up newspaper up into the cell before the insulation has a chance to leak out.

BA

 

[OldBldgGuy]

If the loose fill insulation is vermiculite, it will flow out a mouse hole. You will have an awful time stopping it. I hate exposed surface-mounted angles, but despite the lousy appearance you can make them weatherproof with flashing & caulking. What about 2 angles inserted into the block joint from each side of the wall, toes touching, before removing anything?

 

[allgoodnamestaken]

If the loose fill is vermiculite, you will probably have to do some asbestos remediation if you open up that wall.

 

[EngineeringEric]

Just let the loose fill insulation escape.... the building doesn't have a good thermal value as is. After you do the repairs have them break open the top face shell and fill it with something (loose again or maybe SPF? or something)

You can use an IR thermal camera and see voids if needed if only half the height empties.

building a bond beam like that is not easy... if it even accomplishes your intent of keeping the insulation in place

 

[Guastavino]

Client decided not to do it, but I still got paid. I was going to go with the install a new bond beam approach. I know it wouldn't have been easy, but it would have been the best option by far in my opinion since it's a single-wythe wall.

Thanks to all!