"In-Ground" Pressure Treated? UC4A, UC4B, UC4C...

Old 11-17-22, 08:13 PM
Thread Starter
Join Date: Jul 2014
Location: usa
Posts: 252
Received 0 Likes on 0 Posts
"In-Ground" Pressure Treated? UC4A, UC4B, UC4C...

ok so I found this quickly:

Ground contact wood levels
  • UC4A = Ground Contact, General Use
  • UC4B = Ground Contact, Heavy Duty
  • UC4C = Ground Contact, Extreme Duty
Yes, not all ground contact is the same. Dry ground requires less treatment. But more importantly is how the wood will be use. The more extreme the use, “duty,” the higher the treatment level it should have



Didn't I read on tags before some say 'above ground' or 'ground contact' but also 'In-Ground"?

Maybe 'In-Ground' I saw was UC4B or UC4C, and at a lumber yard or something already built, because I don't think Lowe's or Depot have anything greater than UC4A.

I'm building a shed on 4x4s beams set on 3" tall concrete blocks with fortifier etc in the concrete to make it stronger and the blocks will be about another 3" below grade set on gravel.

The area isn't too wet but does get saturated after very heavy rain and has fence close up to 2 sides of the shed and the house on the 3rd side about 10 feet away , so air flow won't be the greatest.

I know the foundation and beams are going to kill the shed eventually, that'll be what rots out in IDK maybe 65 years and the shed taken down despite the walls and roof etc should be fine or easily replaced instead of having to knock the whole thing down. Come to think of it worst case scenario maybe I'll just write a note in the shed once the foundation rots to have fun with it and just take it apart and rebuild the foundation, but really I'd like it to last as long as possible.

You think it's way overkill and overpriced to source UC4B or UC4C?

Keep in mind not only the 4x4s but also all the treated 2x4s which I'm putting about 12" OC for strength and the treated plywood (likely ply would rot first actually), and all these I want to additionally paint on preservative like coppercoat.

16 foot x 8 foot shed , running three 4x4 beams that cost $30 each as 16 footers. So I'll check the price of stronger threaded lumber plus all the 2x4s and plywood so I'll see if it's way too expensive, plus I get %10 off lowes also but not at lumber yard. Plus maybe coppercoat will bring it to a UC4B or C level.

I know CCA is stronger but illegal for most uses if you can even find it, but would consider that if possible, but on the other hand I'm not super worried about it now I can write in the shed something like just rebuild it with same materials minus the foundation in 80 years or something, or possibly it could be jacked up and reinforced from below but doubt anyone would do that.
Old 11-18-22, 06:27 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 28,330
Received 1,627 Likes on 1,461 Posts
In all that you asked one question. Did I miss one?

"You think it's way overkill and overpriced to source UC4B or UC4C?"
That's up to you and your location to decide. Higher level of treatment should last longer. At the beach house I used the highest rated for the boat dock and seawall because of the harsh environment. Still, after 10 years the wood was still good but definetely showing the signs of being in a saltwater environment. Inland I have old, standard treatment level CCCA posts that still look better than ones at the coast half their age so your environment can have a huge impact.
Old 11-21-22, 11:44 AM
Thread Starter
Join Date: Jul 2014
Location: usa
Posts: 252
Received 0 Likes on 0 Posts
well, I called two local lumber yards, which aren't small yards, and neither have anything above UC4A, both said maybe it could be special ordered but didn't sound familiar with it so it seems uncommon, same with if I could get CCA through them withotu a special permit or something for salt water use or whatever.

I'm just going to build it with the UC4A lowe's stuff, it should be cheaper than lumber yard prices.

I think doing the whole deck (4x4s, 2x4s and plywood) in greater-than-UC4A is going to cost almost double or something so I think it's overkill and really I just hope when the whole shed needs to be replaced in say 65 years that at least the roof and wall lumber any anything else can be repurposed or built into a new shed.

Another option which would last longer than any super-resistant treated lumber and cost less is pouring a 8" thick concrete pad and keeping the sill plates a good few inches above grade like a house, but that's a bit ridiculous for a shed and costly for a 8x16 shed plus I'm doing this in the cold and it would freeze (the concrete blocks for the posts I'm pouring in the garage in plywood forms 5 at a time then immediately brining inside to cure for a couple weeks before putting outside. I'm not using pre cast cinder blocks because I'm afraid they'll rot out sooner being lesser quality concrete with more filler, and I'll be using waterproofer bonder fortifier etc in my mix.

I estimate if a 8" thick pad 8x16' would be 143 80# bags @ about $5.50 each = $858 in concrete plus wood for forms but can re-use that, plus should have rebar/mesh a couple hundred more and maybe fibers mixed in.

A deck with 2x4s 12" OC (I want strong..), 4x4 posts and 3/4" treated plywood would costs about $400. Plus maybe $100 more for a second non treated layer of plywood. Plus about $65 in concrete to make posts.

If I got the concrete poured with a hot mix from someone who knows how to do cold weather concrete, I assume the cost would be much less than $858 if I poured it myself with bags so I'll look into that but for now not going to worry about it and ok with building a deck.

Thread Tools
Search this Thread
Ask a Question
Question Title: