Stupid question about nails and wet wood
I just built a garden shed, used PT in places, and that stuff was wet! So, now we are entering colder weather…I’m guessing there’s going to be a freeze/ thaw cycle in the wood because of the high moisture content…
I used rafter hangers at the ridge and hurricane clips at the top plate to secure the rafters.
So, besides the compressive forces of the wood freezing around the nails (in effect making the nail hole larger when the wood thaws, causing joints to open up) , do I have to worry about the nails in the rafter hangers backing out with some sort of frost heave effect?
Secondly, I noticed when I was cutting that the treatment in some of the 2x’s was only about 1/4 inch deep…you could see a clear band in the center of the end grain. Do I need to seal the end grain of treated lumber?
Replies
Firstly, if you used joist hanger nails, (teco's), in the hangers then you shouldn't have any problem with the nails backing out. Your biggest problem could be cracks and splits. Secondly, yes you should treat the ends of pressure treated cuts. The treating chemical is only designed to permeate 3/8"-1/2", so sometimes you get a 1/4". Jasco makes a good product for this.
I wouldn't expect frost heaves (also called frost jacking) in nails.
In piles and wells, the upper frozen soils can freeze to the pipe. Ice lenses form in the deeper soils as winter progresses and push the upper soils up, bringing the pipe with them.
Later when the upper soils thaw and settle down, the pipe does not settle because it is held in place by deeper, frozen soils that have a several month lag in their freeze/thaw cycles.
I have had enivronmental monitoring wells move up 3 to 4 feet in a couple of years. Weirdest dang thing to see wells going up out of the ground as the years go by.
A real bummer if your house was constructed on improperly installed piles. Houses can get a foot or two out of level from one end to the other.
But I don't see it happening with nails. A 2x10 or 4x4 is going to freeze and thaw essentially all at once. And the wood does have not any silty soils in it to form an ice lens. Every cut a 4x4 in half in the winter and found a ice lens inside? Nope.
Arctically,
I am alwayse more concerned about the sun than the cold as it applies to the connections of my lumber. I still remember one job we were to install a seamless steel roof over wood trusses installed by a framer. The centers had to be on 2' from one end of the building to the other. ( about 120') Somehow they got off and we called them in to fix it before we would put on the roof. They arrived just before we were going to go frame up a small garage. His first comment to me was that the last 3 days had been sunny and hot and warped all the trusses out of line. They just need to be pushed back into there centers. My only comment before I drove away was I had seen the sun pull a nail... but never drive it back in.
Scott T.
Here in non-freezing Southern CA I've seen nails back out of wood on a totally unused deck. I drove them back down, and a few months later they were backing out again. There must be some kind of moisture/temperature thing going on, but I don't have a satisfying explanation of exactly what.
-- J.S.
I'd suspect humidity/water causing the wood to shrink and swell. Nails through decking into joists? Or through joist hangers into 2x stock? Probably not vinyl coated, right?
If you want to do a science experiment, paint one section to help stablize the moisture content of the wood. And compare the nail movement from one section to another.
Does anyone make ring-shank joist hanger nails?David Thomas Overlooking Cook Inlet in Kenai, Alaska
Yes, galvanized thru decking into joists.
-- J.S.
I'm imagining a process like frost jacking, but in which decking swells with water, pulling up the nail. And later locks the nails in their new, higher position. Might be minimized if a large fraction of the nail's length is in the joist.
The 3-1/2" screws on my deck haven't been going anywhere.David Thomas Overlooking Cook Inlet in Kenai, Alaska
---"David Thomas Overlooking Cook Inlet in Kenai, Alaska"---
You get "Country" magazine? It's opening story and beautiful pictures are about Kenai, Alaska. E-mail me your address if you are interested in it.
I guess that you may know about frost cycles and their effect on any materials, living up there.
dthomas(at)alaska.net
A course in Arctic engineering was required for comity of my Civil Engineering PE. A very interesting course. Most students were newbies to the great white north. The instructors and I had great discussions because I was building my own house and already thought about many of the issues.
"Alaska" magazine. Plus Science News, New Yorker, Nat'l Geo, Outside, plus New England Journal of Medicine, JAMA, etc for my wife.
David Thomas Overlooking Cook Inlet in Kenai, Alaska
Ok, I will e-mail you the question of your snail mail address, silly.
I don't know how small your corner of the world is but doubt that your signature will fly at your post office. It would here, because our town has about 120 people, most living out in the country, so we go get the mail at the post office itself every few days.:-)
Try adding Wilson Quarterly, Atlantic Monthly, Scientific American, Cerebrum (Dana Forum on Brain Science, very basic)...
Interesting about the nail. We have some wooden stock pens left, built in 1950 and some of the nails do come out slowly over the years, even the big, corkscrew ones that you can't pull out. I thought that it was from cattle hitting the boards but wondered how they could hit the high ones enough to cause that.
Now I know why.
Oh, that address! Sorry, had e-communications on the brain. 247 N Fireweed, Suite A, Soldotna, AK 99669.
Is "Country" for back-to-land, grow-your-own-wheat, raise-your-own-chickens hippie farmer types? A friend up here wrote a few pieces for such a mag.
Atlantic Monthly would be on the list if I was all caught up with the New Yorkers.
Sci Amer is an odd one. Not hard science like Science or Nature but not fluff for the unwashed masses like Popular Science. I'll scan them at friend's houses and borrow when there's a good overview of nuclear proliferation, international slavery, etc. Their country by country and regional summaries are nicely done.David Thomas Overlooking Cook Inlet in Kenai, Alaska
---"Is "Country" for back-to-land, grow-your-own-wheat, raise-your-own-chickens hippie farmer types? A friend up here wrote a few pieces for such a mag. "---
No, is a farmer's magazine of nice pictures, no ads, stories of regular farm families doing their stuff. Vacuous but with beautiful scenery.
Atlantic Monthly is uneven, sometimes has good articles, other issues are not worth the time it takes to read thu it. Of course, we can learn from all, never know when something will connect the dots for us.
Scientific American is not for the hard science but for the science news (and games).
For hard science, books are better.
Will slow mail to Alaska. Guess that pony express doesn't stop there?