Cutting new opening in thick masonry wall 1

[bhiggins]

Hi Guys and Girls,

I have a remodel project where the architect wants to create a new 12 ft opening in a 2 ft wide limestone block wall. I'm trying to come up with the most practical detail for a new lintel. For thinner walls I've done pinch beam lintels, but I don't think it would work well for a wall of this thickness.

I'm thinking a series of HSS6x6x tubes stitch welded together would work but never used this detail in practice for a retrofit. Here's a detail I've come up with. I'm wondering if anyone sees any constructability issues with this detail or if there is just a better way to detail this opening:

A steel loose lintel angle that works for this span is a L10x10x3/4 each side of the opening. I feel like this size is not practical.

 

[OldBldgGuy]

Use a couple of W8s inserted from each side with 1/4" plates on top. You didn't say anything about the masonry units: random ashlar, regular ashlar, rubble? Regardless, with slight variations allowing for the material, you can cut a slot for a beam from one side 12" deep, grout a decent bearing pad at the ends, insert the beam and plate, then grout for bearing of the masonry above to remain. Repeat from the other side. Then remove the masonry below. Weld a plate on the bottom of the beams afterward and lay in salvaged stone to hide the lintel. It would be pretty unusual if the wall didn't have enough integrity to hold the stone above in place while you do this, and I've seen it done to a lot of walls of widely varying conditions and masonry unit sizes with no trouble.

 

[TehMightyEngineer]

What's the environment like? I don't like all the hidden surfaces if there's corrosion potential in the wall.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[bhiggins]

Here's a photo of where you can see the thickness of the wall, the new opening will be at the second floor. I really like the option of inserting W8X beams without shoring. I don't really understand how they would insert a bearing plate after everything is installed and grouted, do they jack everything up to slide in a plate? Do you bolt the bearing plates to the masonry and weld to the plate both sides? or leave 1 side unwelded to allow for movement?

The project is in Texas with a decent amount of humidity, but the building will be used for offices only. I'll rework the detail and post later.

 

[bhiggins]

Here's a revised detail, what do you guys think?

 

[CANPRO]

I like it. My only comment is that it will be difficult if not impossible to drill a 6" deep hole within that 8" cavity. You'll need at least a 6" long drill-bit of course, which doesn't leave room to drill. Maybe a hybrid of this detail plus your previous one where you had the bearing angle and the horizontal anchors.

 

[TehMightyEngineer]

Typo: Step 1 says ±8' and ±12' instead of " (inches).

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[OldBldgGuy]

I would probably keep the beams to the exterior a bit more and cut down the facing stone to suit, but you've pretty well got it. And it really does work in the field even though there seem to be some questionable things. Before you put the beams in you look after the bearing; I wouldn't get too bent out of shape about the length of the anchors, you're working with stone. Get something in there that holds and can be installed, don't worry about the exact dimension. You can't drill into small/odd shaped/close to edge pieces.

 

[EZBuilding]

Maybe consider specifying hot-dipped galvanizing of the beams?

 

[OldBldgGuy]

Here in Canada I might, and deal with field welding and touch-ups for the bottom plate, but I wonder if it's necessary in Texas. I don't live or practice there though.

 

[kipfoot]

Regarding the details: I'd skip the top plate and use a bf = 8" wide flange beam and leave 2" or so between them. I think the 3" overhang will be okay and make for a cleaner finished mortar joint. As others have said, it'll be tough getting those anchors in.

This is one of those comments that doesn't answer your question: When I look at this building in google earth view, it doesn't seem like the parapet wall between 1204 and 1206 is as thick as the 24" pier that you've dimensioned, and a 24" thick wall seems very thick for a two story building. Sometimes I like to double check the obvious before sending a detail out.

 

[OldBldgGuy]

Yes, the top plate is always a question, that's why I noted that there was no info on the size of the stones. If it is random rubble, a few inches of overhang could be a problem, but the photo posted later shows nice large ashlar pieces which would easily sit on a narrower beam without a plate. The thing is, you can't count on an interior or demising wall being built like an exterior wall, and as kipfoot says, you can't count on it being built like the end face you see, either. You won't know until you physically investigate the actual beam location.

 

[bhiggins]

Thank you everybody for your input, this has been super great and helpful. The demising wall already has some openings so we were able to observe and measure the thickness of the walls. The walls in the space were covered in plaster so we didn't get a good look at their composition or quality. This detail pertains to only one new opening so I am fine with being a little conservative if the site conditions do not match our expectations.