Timing of Wood Shrinkage Problems in Mid-Rise Buildings 2

[abusementpark]

How long after a 4 or 5 story wood building is occupied where you can say any problems associated with wood shrinkage would have presented themselves? I am thinking about a year after occupying should be plenty of time, but wondering if the risk is still there beyond that.

 

[JoshPlumSE]

I've seen wood shrinkage issues crop up YEARS later. Granted, I'm talking about checks in relatively large sawn lumber beams.

Also, the concept of differential shrinkage between wood walls and other architectural elements (cladding, drywall and such) seems to be something that also takes a fairly long time. Though it is usually ignored in the type of wood building 1 or 2 stories that I've worked with, I could definitely see it being problematic in a 5 story building that has some windows or cladding that are not designed to acomodate movement.

 

[driftLimiter]

The drying rate is a function of many variables including the type of wood, construction practices, relative humidity and temperature, etc.
Its difficult to have a decisive estimate of the shrinkage time. That is why we see shrinkage take up devices that are designed to move along with the shrinkage continuously.

There are certain effects of shrinkage that might not 'present' themselves until the building sees ultimate loading. For example loose straps or hold down anchors wouldn't be a detectable issue untill a large wind or seismic event, then the effects can be severe.

This document probably gives designers everything they need to address this issue. Link

 

[KootK]

While there are lots of conceivable exceptions, I feel that a year is likely plenty as well. That takes the moisture content of your wood from wherever it started to, hopefully, a state consistent with the conditioned interior of the building. It also gives any exterior brick a chance to see one version of each of the four seasons.

I've only had real world shrinkage problems twice in two decades and both materialized within a few months enclosing the affected portions of the building. Wisconsin for what that's worth.

 

[EngineeringEric]

The majority of the forensic projects that we get involved with are within 1-2 years after construction. Now we have had some that are 5+ years after construction but that doesn't mean the issues occurred and weren't noted or addressed for years later. Date something is seen is not equal to the date it occurred.

We run into the worse issues at brick veneer. brick doesn't shrink and the wood backup does... therefore the window openings have problems and the transition from veneer to siding (siding attached to wood wall and veneer not. you need a 3" gap here during construction to allow for flashing after the building shrinks and brick expands

 

[IRstuff]

My doors took about a year from the time they were installed to when the facades shifted from the cores, as indicated by the splits in the facade paint along the seams of the raised panels

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[abusementpark]

The majority of the forensic projects that we get involved with are within 1-2 years after construction. Now we have had some that are 5+ years after construction but that doesn't mean the issues occurred and weren't noted or addressed for years later. Date something is seen is not equal to the date it occurred.

This is good to know. I understand there is always something that cannot reveal itself until certain conditions are met years later, but it seems like the vast majority of issues would occur pretty quickly.