Reducing the opening size in a masonry wall +

[Ninjahedge]

I have a weird question.

on one project I am working on, there are masonry walls on an old structure that have been extensively remodeled over the years.

Lintels have been placed and windows and other openings added and sealed.

My question lies with one area. The owner would like a smaller opening (with a door) where a large opening now exists. I have read a bit about the notching methods for adding a lintel in a load bearing wall, but what can be used to remove and replace it?

The reason for this is to add to the buildings lateral stiffness by bonding a new section of masonry wall to the remaining existing. Other areas will have new openings placed, and I would like to preserve or improve the buildings stiffness by lengthening the shear walls where possible.

Any clue on the means and methods for this?

TIA!

 

[SLTA]

What's the age of the building? What type of masonry (brick, unreinforced CMU, reinforced CMU, structural clay tile, etc)? How are you analyzing the existing building stiffness?

I'd recommend not removing existing lintels, but working with them and around them. I can offer more advice once we have more information.

 

[MiketheEngineer]

YES - agree slta

 

[Ninjahedge]

Building is turn-of-the century and designated under historic preservation.

It is a three story unreinforced masonry building.

The lintels I am looking at seem to be 8WF's or equivalent spanning approximately 10-15 feet (depending on the opening).

The problem is, I am looking for a way to support the brick and the floor above while infilling the wall and reducing the lintel length.

Right now, building stiffness is evaluated empirically by relative cross sectional area along the line of action (number of wythes and LF of shear wall in the direction under consideration).

It is a single family and is exempt from seismic design requirements, although the NYC code does recommend trying to preserve the original building behavior. I am filling in any unused pocket doors and trying to maintain the same basic net shear area on 1:1 L/H ratio walls or better (if possible).

Thanks for the replies guys. Hope this fills in the blanks.

 

[SLTA]

Best thing then is to put back somewhere else what you take out. Try sawtoothing in the infill brick to the existing brick, and bridging over the existing lintel somehow - perhaps with steel plates, attached from new brick to old brick above the lintel, to support the top of the infill? Be sure to use similar-strength brick (ie weak, on the inside of a building) and probably a lime-based mortar. Modern bricks and mortar are too strong when compared to historic materials, and you'll get a whole ton of other issues to deal with if you use new mixed with old.

NYC has some pretty strict regs on preservation, as I'm sure you know, so just be sure you're not missing any of those. Sounds like you've looked at that.

Good luck!

(ps - I'm not a guy ;D )

 

[Ninjahedge]

slta, thanks again.

BTW, it does not matter to me what you are, you are still one of the "guys" when it comes to structural advice!

Anywho... I read what you were talking about with the Lime base mortar instead of others. I think what they said was the strength and rigidity of modern mortar is rather punishing to the older brick and is also not as in-sync with the humidity/temperature expansion/shrink of the older brick.

i would imagine that using different materials also raises the possibility of chemical interaction, but without doing a bit of research on that, suffice to say I know that it is just simply not recommended.

Steel plates may be difficult in this since they want to keep the brick exposed (to my knowledge). unless we need to thicken the walls out because we have no other recourse, splicing around the lintel is not really feasible.

Also, using the beam itself as a shear transfer is not likely. I do not want to shear stud or attach this steel to the brick for fear of incompatible expansion/contraction cycles that may produce cracking....

The only solution I see is to set the details up and see what comes back from the contractor as to meas and methods....


Thanks peeps! (Especially you slta)

 

[SLTA]

I'd say leaving the lintel in place is more about not messing up any more of the building than need be, than about any shear transfer.

Check out the Preservation Briefs (

http://www.nps.gov/tps/how-to-preserve/briefs.htm),

especially 2 and 41. Also check out the BIA Technical Notes (

http://www.gobrick.com/TechnicalNotes/tabid/7658/Default.aspx),

especially 8, 8B, 11E, 15, and maybe 46, with others as you see fit.

Any book on structural renovation, especually "Structural Renovation of Buildings" by Newman, would give lots of info, too.

Good luck!

 

[MiketheEngineer]

You could possibly shore the building and remove the lintel. We do this all the time.

But with a building this old - I would prefer to just infill and grout over the lintel to hide it.

 

[Ninjahedge]

Mike,

Shoring it would be something I would be interested in knowing the specifics available to hold up the current masonry above the header beam. i know you can poke holes through, but that becomes rather hard to put things back together later.

Is there any way to try and use the portion of new wall under the steel lintel to help with the lateral load? Getting the load down through that lintel into the new wall extension may be limited...