Pressure Treated or Not?

[robertwhite]

Need to replace a couple of floor joists in a 60 yr old kitchen. Original joists are oak that is now hard as a rock. Unfortunately, a couple are cracked and I'm not comfortable leaving them.

Joists are 18" above dirt floor (floor has no vapor barrier) and there is tar paper anywhere the joists sit on. Now obviously, by code (even though we don't have codes here), PT is not required. I am however more comfortable with having a PT vs regular lumber just for the dampness factor.

Here's the issue........... If I use PT, when it dries out and shrinks, won't it take my floor with it and pull the floor down?

So do I use regular interior lumber that won't shrink or use PT and take my chances on it pulling the floor down in that one section?

 

[tipsy]

Buy pressure treated and wait 30 days for it to shrink and dry out before installing it?

 

[Milton Shaw]

PT will warp and curl as it dries out. I would use Number 2 construction grade and then if you can put some metal shields on the ends to protect from moisture/bugs.

 

[dutchgray]

Or set them a touch high so when they shrink it ends up level, if you cant wait to do the job. Or just sister on to the cracked ones so it don't matter when they shrink.

 

[CNGsaves]

So . . . . RobertWhite . . . . are you . . WalterWhite's brother ?? . . . from BB ??

You out in desert of New Mexico ???

. . . . . seriously, WHERE is here ??

Update GJ Profile with City/State/Country.

You'll get best advice when supplied with more information.

 

[robertwhite]

Buy pressure treated and wait 30 days for it to shrink and dry out before installing it?

Can't wait, has to be done now.

Or just sister on to the cracked ones so it don't matter when they shrink.

That is what I was thinking, and probably what I will do. The old joist is not rotted, it's just got a long (2ft) crack in the middle, so sistering should work.

 

[Kevin54]

Buy pressure treated and wait 30 days for it to shrink and dry out before installing it?

The only bad thing about laying it out and waiting 30 days for it to dry out, it will be twisted and warped something terrible. I would get it, and fasten everything together the way it is when you get it. It will help eliminate some of the twisting and bowing.

I have a 6x6 post that I was going to use for a porch post, but it has twisted around probably 10-15 degrees from one end to the other, so it will get used as a fence post where I can hide most of the twist. And this post has twisted even though it has (6) 80 lb. bags of concrete sitting on it.

Are you replacing the current joist, or are you going to sister joist beside the ones you need to replace?

 

[Leaflessshadetree]

Use regular construction grade lumber but waterproof it with your choice of sealants.
Pressure treated wood will eat most nails and fasteners.

 

[WVBrady]

Can't wait, has to be done now.




That is what I was thinking, and probably what I will do. The old joist is not rotted, it's just got a long (2ft) crack in the middle, so sistering should work.

I would sister it with the best waterproof glue you can get and draw them together with screws, then use nails for increased shear strength.

 

[rburke65]

I would think you would be better off sistering the joists. Wouldn't it be less wor also?

 

[curliejones]

The only bad thing about laying it out and waiting 30 days for it to dry out, it will be twisted and warped something terrible.

 

[curliejones]

Pick through the stack and get straight grained boards that are cut straight to begin with. Sight down the board and/or place them on a level floor on edge to see if it's straight. Lay it on the flat side when you get home supported at least every 3 ft and place a few concrete blocks on top. Keep out of the sun to avoid drying one side much faster than the other, but make sure the location has good air flow. Move blocks and support every 4 days. Alternatively: try to find KDAT - I understand that kiln dried after treatment is available but I don't know where around here.

 

[Catadj78]

Sister it with pt. Use hot dipped galvanized nails.

Nail it up when you get it, it will be fine

 

[captaindiode]

You can buy KDAT (kiln dried after treatment) pressure treated. You may have to hunt for it at a real lumber yard instead of a big box. Yellawood is one name brand. Also, if you use PT, remember that all fastners that enter the lumber must be hot dipped galvanized, ceramic coated, or stainless. The copper content will corrode anything else in short time.

 

[Cyberbear]

You don't mention the span of the existing oak floor joists, or the size of the present in place joists. Based on the small amount of information, I could suggest the previously mentioned sistering is a good idea. You may have the option of doing both sides, if necessary, as well as putting a couple of ready made concrete piers set on 12" concrete stepping pavers to support the existing floor joists that are 18" above grade. This should more than correct any existing and future settling problems. They also sell economical foundation screw jacks that you can adjust, as needed, over time for another type of quick fix.

 

[Chris705]

And put down a vapor barrier on the dirt!