Lateral load transfer into existing multi-wythe brick exterior wall

[TroyD]

Please refer to attached illustration for building layout with proposed addition. The addition is small so the additional lateral load is insignificant, and the sidewall is lengthy for absorbing the load, but the existing building is c. 1880 brick construction, in good condition. (Your typical small town main street building). I have sketched a suggested connection using threaded rod penetrating thru the existing wall and fastened to the inside with a large steel plate and nut. The owners are keen on the industrial look of the exposed steel plate, painted black. I am proposing a total of four rods - two along the bottom chord, and two along the top chord to maintain stiffness.

Just looking to get some input from others who may have more experience with transferring lateral loads into existing brick. Any info you can provide is appreciated.

-Troy

 

[sticksandtriangles]

Troy,

No additional information on my end, but what you have shown is my standard detail as well.

For discussion's point, at what point do you begin looking at the existing brick wall for the increased lateral load? I am not too familiar with the IEBC, but I think I remember something of the tune of if you increase the load to the wall by more than 5% ~ 10% (can't remeber the number) you need to evaluate your brick wall?

I am also remember something in the code regarding evaluating the demand capacity ratios of the existing brick wall to see if they change by a certain percentage. Given that this is unreinforced masonry, this feels like a somewhat difficult task in these typical "shot gun type" existing buildings.

I am in a lot of renovation work right now and may even open up a separate discussion on this as I have definitely side tracked the conversation.

-S&T

 

[DaveAtkins]

How are gravity loads supported?

I think the truss supplier will use a double vertical member at the brick wall, with the vertical member closest to the wall supported on your ledger, and the other vertical member continuing down to the bottom chord of the truss.

Also check the ledger for the gravity loads, since they will cause the bolt to act perpendicular to grain.

DaveAtkins

 

[OldBldgGuy]

I think Dave has highlighted the bigger concern: vertical load on the ledger. 2 rods aren't enough for that in 22', especially through a small ledger such as you show. Through bolts are the way to go because anchorage of expansion or chemical anchors in old soft brick is questionable at best, but check the bearing of the rods on the brick and the capacity of the ledger with the bolts acting perp to grain. I'd ask the truss manufacturer to use a wider vertical web at the brick wall and shorten the bottom chord 1 1/2" so the ledger effectively sits in a notch in the back end of the chord.

 

[TroyD]

Thanks for the responses. Regarding the gravity loads, I propose a LVL girder beam offset approx. 2 ft from the brick wall. (The roof trusses for the addition will have a 2 ft cantilever at the existing wall). (Refer to attached illustration).