Repair of racked / laterally displaced wood framed building

[Labs763]

Hello,

I recently performed a site study of an existing building that is racked / laterally displaced up to about 4 degrees from vertical (for a client looking to purchase it). It is an old building, probably around 100 years old, with several renovations and additions over the years. It is not large - two stories, maybe 2000 sq ft total. It was likely a house that got converted to a 1st floor commercial, 2nd flr residential building.

My primary findings determined that the two longitudinal (exterior) walls exceed allowable slopes that would be considered acceptable for a wood framed structure that was not designed to handle this situation. Additionally, there are 4ft tall masonry stemwalls that have a different slope than the wood stud walls that bear on top - a hinged condition that likely has negligible attachment. It is possible this used to be the first floor elevation, and then it was removed and a concrete slab on grade was installed at grade. There are a lot of other issues going on that contribute to the leaning (differential foundation settlement) or are independent (roof leaks, no rafter holddowns even though a completely new roof and roof sheathing were installed, etc).

The owner of the building has submitted an engineering report to contest mine. This engineer has overseen the renovations of at least two other renovations dating back to 1999. He has established that the building is currently stable and adequate. The owner submitted previous reports from the engineer that do indicate he knew the lean was a problem. From what I can piece together (there is no set of repair drawings, just a few crude hand sketches and emails), he added transverse walls with Simpson CS16 diagonal straps (no plywood/osb), and just generally said that would hold it. These transverse walls were simply placed on top of the presumably 4" concrete slab with negligible anchorage.

This forum has discussed the usage of CS straps for lateral bracing in the past, and I believe the consensus is that it cannot be established they will hold any notable load. Especially when there are no gusset plates at the corner (which there are not in his sketch), we are talking maybe several hundred pounds of resistance from the nails at the top corner in the top plates. Attachment at mid-height interior studs do not offer resistance.

So on to my ultimate question: repairs of racked buildings. My recommendations are to remove interior and exterior sheathing (gypsum and any plywood/osb they might find) and mechanically replumb the building. Not only can the CS straps not adequately restrain against wind/seismic (this is a hurricane region), they also cannot restrain against P-delta forces that could develop from a max live load on the second floor. Could anyone offer differing opinions? Hypothetically, could one justify that plywood shearwalls can restrain against wind/seismic and long-term lateral P-delta forces without releveling? My originaly opinion was that they cannot, but I guess that is what TJI joists are doing.

Thank you for the help.

 

[XR250]

So that is about 16" over 20 ft of height? That is a lot! it is hard for me to imagine any engineer saying that is ok and using CS straps to make it stable. Probably gonna be a pissing contest between all involved, however.
Not a job I would personally take without a pretty tight contract limiting my liability.

 

[phamENG]

I have a client who had a similarly racked building. We designed a replacement.

The trouble is that as wood deflects and deforms like that over time, it creeps and deforms permanently. If you try to undo even 10 years of severe deflections in a week you'll probably end up fracturing lots of important stuff and ripping apart more than a few connections.

If the second floor is in decent shape, you'd be better off shoring the second floor (steel beams with cribbing tight to the underside of the joists) and replacing the first floor walls altogether.

I agree the CS straps are not adequate for this. You have 200 or 300 lbs of capacity in that strap maximum...and you cant increase it for wind load since it's trying to restrain out of plumb induced lateral live and dead loads, too.

 

[Labs763]

Correct, you can easily see the lean with a naked eye from the street. I was surprised, but I have both a report from several days ago confirming that the building is stable in its current state, and the repair "notes" that indicate what work was performed in the past.

To clarify, my scope at this point is to provide a feasibility assessment. I agree with you XR250, and will certainly not accept any sort of design role in the future without what I would consider adequate repairs. In all likelihood, my client is going side with the other engineer if they decide to purchase it so that they can avoid IEBC upgrades when they start interior renovations - but that's how things go. I was hoping to find someone on here to explain why I might be wrong or overly conservative.

 

[phamENG]

In theory you could probably justify some sort of plywood shear wall to take the P-delta and wind load to call it stable, but I would be very hesitant to do so given your description.