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Siding unlocking / popping out at 2nd floor level of 2 Story

Siding unlocking / popping out at 2nd floor level of 2 Story

We have been seeing this more frequently:

Determine cause of loose/unlocked siding. Mostly aluminum siding but some vynl siding on 2 story homes usually a 2 story gable end wall with few openings. The siding is popping out or coming loose at the rim board. This is frequently only the panel at or near the rim board.

The rim board is shrinking more than the stud wall and thus pulling the siding panel down and popping it loose. Over driven nails (they should be installed loose) are also contributing.

Any other thoughts or references that discus this? Is there a standard installation manual?



RE: Siding unlocking / popping out at 2nd floor level of 2 Story

I think you are considering the right issues with fairly concentrated band jst. shrinkage.  Lack of openings means more extended surface of the mat'l. with little flexibility offered by shorter pieces around openings, etc.  Is there any consistency in the opening joint's location or nail line location w.r.t. top or bottom of the rim jst. or sill pl. and top pls., all cross grain shrinkage?  What about a gable wall which is balloon framed?  Loose nailing is all important.  Maybe pay attention to season or temp. at time of installation; if hot and expanded siding, install slightly loose  vertically  because you know the siding is going to contract, but not very loose or you get what you are seeing.  The opposite thinking and considerations when installing in cold weather.  I think I have that right.  Maybe the nail line at mid height of the rim jst. would distribute any movement to two rows of siding mat'l.  Note that south and west facing walls see much more movement of the siding.  The siding gets much hotter than the framing, and the coef. of expansion & contraction for aluminum and vinyl is several times that of the constant temp. wood.

RE: Siding unlocking / popping out at 2nd floor level of 2 Story

I agree with shrinkage issue too.  Rather obvious.

Then I would have to assume that solid sticks were used for the floor joists rather than TJI's?

Mike McCann
MMC Engineering

RE: Siding unlocking / popping out at 2nd floor level of 2 Story

well...I really think it is just poorly installed siding otherwise I think you'd see it more often than you do.

I can recall being called back to a house in the spring that we built in mid January. The siding on a gable end was a damn mess starting at the bottom of the gable. Below that it was fine as was evident that all the siding matched up around the corners. The proper expansion of the siding was not allowed for where the siding was cut and fit into the j-channel going up the gable. This is very difficult measurement to get just right in any weather and is especially hard on low pitched roofs where the angle cut on the siding is very "long". As the siding expands in warmer weather, it pushes into the j-channel and the slope pushes the siding down and it comes unhooked.
We pulled the siding down and by time we re-worked it to the top, we had an extra course left over (really just  a small triangle piece). ....point being a little adds up to a lot.

Another huge issue is gable end frames that are built using gable trusses. IMO these are junk as they are made from 2x4s going the flat direction and are notorious for warping badly. The verticals are only 2'-0 on center usually so the carpenter often only nails into the osb sheathing which does not hold siding nails very well. As the truss warps, the nails and siding pop.  

RE: Siding unlocking / popping out at 2nd floor level of 2 Story


Toad makes a good point here.  Just want to clarfify though...  Is the siding popping at the 2nd floor wall top plate at the junction with the endwall truss, or at the bottom plate that is sitting ovefr the rim board at the floor level?

Mike McCann
MMC Engineering

RE: Siding unlocking / popping out at 2nd floor level of 2 Story

Reminds me of another issue...some carpenters take the term "rough framing" to new levels...

I have seen where the junction of the first floor top plate, the second floor rim joist and second floor wall bottom plate were all out-of-wack so bad that the siding in the area was bowed outward....predisposed to popping.

might be what M^2 is getting at.  

RE: Siding unlocking / popping out at 2nd floor level of 2 Story

Or another scenario...

This could also happen if the rim joist is an LVL, but the floor joists are solid sticks.  The rim joist would not want to shrink like the joists causing differential shrinkage at the outside wall, possibly affecting the siding?

Mike McCann
MMC Engineering

RE: Siding unlocking / popping out at 2nd floor level of 2 Story

Thanks guys. Good feed back.

I think that improper installation is part of it. It is mostly witnessed at the first floor top plate / second floor bottom plate at the rim joist. But there has been some at the 2nd floor top plate and attic now that I look more closely.

I tried to think of why we/I don't see it more if it is a shrinkage issue:
1.) Usually a freeze board is placed at this location.
2.) If properly installed (loose nails) may not occur.
3.) Use of engineered lumber as opposed to sawn.
4.) Adjusters have paid for this as wind damage.

As far as engineered wood vs sawn wood I think this is an unknown. As many times we can not see the floor framing. Mike what did you have in mind regarding differential shrinkage?


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