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MC Changes & Wood Movement Due to High Humitity3/3
Being in the custom moulding and trim milling biz, I'm always concerned about my wood and trim's MC content. Even though my shop does everything we can to keep things in line, the problem is after its delivered and before the warranty expires.
Last spring I milled and delivered a rather large trim order. We delivered and stacked it into the new construction house where the trim carpenters (not my guys) would do the install. Now I find out that because of lack of room, after delivery the trim is moved outside and covered loosely with a tarp where it stayed, loose packed for a month as they used it.
In the spring, in a high humitity enviroment, loose packed and barely covered, how much MC gain do you think unfinished poplar would gain in 30 days??
Well, now guess what????
Looks like you need to add another line to your warranty. Must be stored in a conditioned area. Outbuildings and outside void the warranty.
If they admitted they stored it outside I'd just use that as the reason to void the warranty. Any carpenter worth his salt knows that you need the moldings to acclimate to the normal conditions in the house before you start the install. Flooring is the same way.
I used to run into this all the time when the housing market was exploding, and registered idiots were building 2m McMansions. They would put the trim in the garage. The one with no door.
There were too many jobs to track, so I learned to read the miters after install and the real house HVAC was turned on. Open at the toe meant it was swelling, gaining MC. Open at the hell meant if had absorbed MC, but was now giving it back.
We merely added a doc to all estimates and ship tickets that explained proper molding storage. The lumber salesmen were then trained, so they could give warnings to the alleged builder.
Do they store the hardwood flooring outside too? Tell them it needs the same treatment. Wood is wood. And because this was the way I first read the title, I'd like to petition for the title to be changed to; "due to high humility"!
Sorry to hear about this issue you are dealing with. That's a bummer. Sometimes it's a fine line between keeping the customer happy, keeping your reputation and not having to accept responsibility/loss $.
I would caution that just saying,"material needs to stored indoors" is not enough.
Thanks for the responses and info, but:
What do you think would be the MC gain in poplar trim sitting outside in a spring, humid southern state for a month????
I realize this would be a guess, but if I can come up with something close, I can then use the worksheet in Woodweb to determine the amount of swell/swrinkage
What did it start out at? The drier it was, the more it will gain. Naturalization of wood outdoors would be in the area of 12-16%MC. Indoors it's suppose to be 6-8%.
IN a month I'd say you could gain 2-4% points.
In some sections of the country, during the rainy season, I bet the outer boards will gain 10% or more. Some will likely have water sitting on them.
Thanks again for all the info and replies. Seams like everyone is on the same page.
Anyone have a good disclaimer they would share concerning this problem that they put at the bottom of their bill or invoice???
My rule of thumb is most species of flat sawn wood will change 1% in width for every 4% change in moisture content (MC).
If you delivered the wood at 7-8% MC that means your shop was 40% relative humidity (RH) at 70F.
The big unknown is what were the conditions when the wood was stored outside. You can go online and look up charts on average temperature and RH in your area. But the conditions that month could be much different.
If the RH was 75% at 70F , when stored outside, the MC of the wood would increase to approximately 14%. That is a 7% change in MC. If wood moves 1% for every 4% in MC that is about a total of 2% change in width. Therefore a 12" board would move about 1/4" (12"x.02=.24").
I don't know if that helps, good luck.
Lots of issues
See attached; they don't sign something similar we don't deliver.
If 30 houses fail and 30 home owners sue, cost to defend is huge, insurance may not defend,
IF the GC does an liability wrap that covers everything then the indemnification and insurance may not matter.
Click the link below to download the file included with this post.
I was thinking this:
"Central Humidification Systems are highly recommended when extensive millwork is being installed."
You suggest adding humidity? My experience is the opposite. From plaster or drywall mud drying, curing basement concrete, gallons and gallons of latex paint, etc....Humidity around home construction is sky high!
Yes, sometimes I think the humidity needs raising. We know the humidity needs to be between 45 and 55%. I've seen some houses where the humidity was 30%, and this was in Arkansas.....
I would visit all the jobs as trim was being delivered - within a day or two. I'd mention to the carpenters that they were "mitering at their own risk" since no matter who gets blamed, they would be doing the reworks and fighting to get paid. This was after the paper explanation of not putting finished wood products on site before the site had dried out sufficiently.
I would use a sling hygrometer and a moisture meter and record info as I walked around the job.
This would send the carpenters to the builder or project manager. They would mention the hardwood guys - checking subfloors for moisture contented waiting until the real HVAC is on and the place drops below 40% RH. They would mention me and my 'instruments' as one put it.
If the carpenters did not do my work for me or were somehow ignored, I would then send my temp and RH data to the builder, framed in a simple scientific format, and could easily show that they were inviting problems. This always did the trick. I did have angry builders make calls and get all upset because of this. I would point out this was not a subjective call on my part (made to cause him problems), but an objective call based upon fact.
I became 'the expert' on the topic and was asked about flooring, tile and other things I knew nothing about. I did keep on hand a couple of mitered joints that had each failed - one to shrinkage, one to expansion - as a pass around that easily explained what I had discovered. This was considered the final step - tell them what you are going to tell them, tell them, then tell them what you told them.
No one had ever had anyone pay this much attention to their projects, so they became loyal customers. And the miters were tight, so the carpenters and everyone was happy.
We have three masters to serve in this work: the Owner, the Builder, the Carpenter. Each has their own goals and demands. Pleasing all 3 makes for a very successful project.