Aligning Engineered & Conventional Lmbr
BuildSmartNJ
| Posted in Construction Techniques on
Just had an addition put on the back of my house, approximately 21×30. The architect called for the main beam of the first floor to be a doubled micro-lam (~3x 9 1/2) while the rest of the floor was 2×10’s – some hung off the micro-lam while others were run in parallel.
Now that the conventional lumber has shrunk I have a dip of almost 1/2 inch over a 6 foot span in my kitchen floor where the 2x10s parallel the micro-lam. Is this an avoidable problem? Do I blame the builder or the architect? How do you tie together engineered and conventional framing materials?
Thanks
Replies
As a framer I often see plans specifying that we hold the conventional lumber 1/4" higher than an engineered beam when flush framing. We have come to adopt that in recent years as SOP. Who's fault? I really dunno. If it wasn't specced on the plans you could probably point a finger at the architect.... but he may have assumed that the builder would know better. Tough call.
1/2" seem like a lot to me. Were the 2x10's green or kiln-dried? Exceptionally wet? I recently saw a similar situation on a buddy's job where the floor system consisted of steel beams, conventional lumber, and LVL's all in about a 10' x 10' area. That floor dried into a bit of a mess in that area. He ended up tearing up the subfloor and ripping tapered shims.
>> I have a dip of almost 1/2 inch over a 6 foot span in my kitchen floor where the 2x10s parallel the micro-lam. << Are you sure that one or more joists were not crowned properly? Crowning is the process where the carpenters look at each floor joist during installation and put the "bow" up. A trip underneath with a long strate edge, string line, etc, would tell you real quick. I really kind a doubt that the 2x10s shrunk a 1/2" in height. Unless there was, say a 1/4" low spot to start with...
Edited 10/27/2005 6:37 am ET by Matt
BuildsmartNJ,
Saw this a few days ago and meant to get back to it but never did. I'm going to take leap and assume that the NJ at the end of your name means you live in New Jersey?
I have to assume that since some of the joists parallel to the LVL that they are running the (roughly) 21' direction?
For some reason soaking wet green lumber seems to get used more in New Jersey than anyplace I've ever worked. Don't know why and can't explain it. I've gotten loads from a yard that were so wet that spreading a dozen floor joists on the foundation would ensure that you were soaked from shoulder to waist. Even after a dry spell of a few weeks or longer.
I have also seen floors such as you are talking about where even with the joists crowned properly, the combination of less than high quality lumber that is still wet and an LVL running parallel will result in just what you have on your hands. The LVL will not shrink and the joists will. Add to the fact that the span is almost 21'. And pile on top the fact that it's green lumber?
Before you start gathering up everyone involved and shooting them out behind the porta-john, does that LVL run a clear span or is it supported by post or pier in the middle? If it is it might be pushed up thereby making your floor seem worse than it is. If not? Wish I knew what to tell you. It's probably no conselation to know that there are plenty of floors out there just like yours for the same reason.