pressure-treated wood for deck joists?

beiley

We've hired a contractor to replace our collapsed deck with a new Trex deck. I'm wondering whether we should be using pressure-treated wood for the joists and supports? Our contractor said that we did not need to use pressure-treated wood because it isn't in contact with the ground. (The support posts have concrete blocks to stand on.) Hopefully my contractor knows what he's talking about, and we don't need pressure-treated, but I was looking for some confirmation or advice.

Thanks,
Mark

CrossWorks

About 22 years ago I built a deck for my soon to be Farther-in-Law. Last summer I replaced the decking "only" and the PT framing was still as solid as "Day 1". When a contractor says what yours said, I suspect two things:

#1. He didn't figure it in the price.
#2. Or the deck is fully under cover and out of the elements reach.

There have been a handful of decks and porches built prior to the "PT Lumber age" that I have taken down over the years, and the number one location for rot to occur is where the nail drives into the wood. It makes a perfect wick for water to get in and do it's damage. So I suspect your contractor may be one of two: Young and inexperienced, or middled aged and not so honest. Then again...who am I to judge.

Just be prepared that if you insist on PT (which imo should of been the first approach by the contarctor) then expect to pay more for the job. How much more??? It all depends on the pricing in your area. But just to give you an example; Here in Maine I pay these prices:

• 1- 2 x 6 x 8' Spruce $4.43
• 1- 2 x 6 x 8' PT Lumber $5.97
• 1- 2 x 8 x 12' Spruce $7.68
• 1- 2 x 8 x 12' PT Lumber $11.45

So now you have an idea that the difference should not be to bad.

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Gary in WA

Where I live, all outdoor - open to the weather- structures have to be pressure treated. I would contact your local County Building Department for answers. Find out before it is too late. It depends on locality.

They do not "have concrete blocks to stand on." Here is their site:

http://www.coconino.az.gov/uploadedF...20Dwelling.pdf

Frost Line – Frost line Depth shall be thirty (30”) inches in Coconino County with the exception of Oak Creek/Sedona, Marble Canyon, and Greenhaven, where depth shall be twenty-four (24”) inches.
EXCEPTIONS – Detached accessory structures located in residential zones for private use, sized less than one thousand (1,000’) square feet, single story, and may have a foundation depth of eighteen (18”) inches into undisturbed soil. Be safe, GGBAR

beiley

Thanks for the info. The deck is not covered. It is in northern AZ, where a lot of snow falls. It sounds like it should be built with PT joists/posts. My contractor stated in their initial bid that the under pinnings would be built with "standard or better Doug Fir". Unfortunately, I used this bid to get reimbursed by my insurance company, so if the job price goes up now I guess I have to eat the difference...

Scuba_Dave

Water will collect under the edges of the decking & rot out the joists

PT is a must

I hope Trex has improved their product

curapa

You need to stop your "contractor" right away and find a new one that knows what he's doing. The cost difference between PT and untreated fir is not that much. If you do decide to keep the same "contractor" on the job I would make him eat the cost, it is after all, his fault.

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Scuba_Dave

GBAR makes a good point
If this is attached to the house then it needs footing below the frost line

How many estimates did you get before going with this one?
Why did the last one collapse?

Caddyshack

Curapa is right.
Check the building codes. PT is probably required. If so, then your contractor is building in violation of code and should be liable for most, if not all, cost difference to PT. He shouldn't be in business if he's going to quote un-treated when PT is required.

Good luck.

beiley

Wow, thanks for all the advice. Now I'm rather nervous. I already paid him 1/3 the cost of the job. He is in the middle of removing the current deck that collapsed. This contractor built my neighbor's house, and was recommended by my neighbor. He was very happy with him. I trust the recommendation, as I know my neighbor quite well. This contractor is from the area, so I would think he should know the regulations. There hasn't been any talk of a building permit. Do I need one to replace an existing deck, with one the same size?

The current deck collapsed because it didn't have enough supports in the middle. There was a section that was only supported at the edge, and at where it connects to the house. It broke off where it was connected to the house under a heavy snow load. The contractor quoted that he would provide supports at 8' centers on the replaced deck. These support posts are currently on concrete slabs. I'm not sure of the right terminology, but they look like they are in the ground, and not just sitting on top of the ground. They look like they are about 16" on a side. I have no idea how far into the ground they are.

I will call the Coconino county building office to ask about PT.

Thanks.

Scuba_Dave

If building without PT & it is called for by code they can make you take it apart & fix it. Might not happen, but not really worth the problem to go with reg wood VS PT. If a building permit is required & one is not pulled they can fine you

Knowing the regulations & following them are 2 different things

Posts need to be secured to the metal brackets
Then the metal brackets need to be secured into the concrete
If the posts do not go below the frost line then freezing & thawing will stress the connection to the house. Possibly causing failure

beiley

I called the county, and the rules here are that anything 6" or more above grade are not required to be PT.

curapa

Required or not, PT is needed for exterior applications. I would call him on it, you do not want to be paying someone else for the same project in a few years.

Check out these sites by professional deck contractors, all framing is PT.

http://www.builtbymac.com/

http://www.winchesterdecks.ca/

http://www.decksetc.ca/

http://www.alscustomdecks.com/

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beiley

Thanks for all the help and advice. I am planning on using PT. I will pay for the difference though, as his initial quote didn't include PT, and was within building codes in my area. I am spending a lot on the deck and Trex, so I want the joists/supports to last the same long time.

CrossWorks

Not sure if you've every heard of CorrectDeck decking, but the product is made here in maine and I designed and built this deck a couple years ago using the CX Decking which has intergrated deck fasteners. Is guaranteed to not have any mold or they'll replace it.

Check it out: Yarmouth Deck


And the entire frame was PT. Oh...and here's the site on the decking

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Mop in Hand

Let's not confuse pressure treated with treated lumber, there is a difference. Your contractor is right "pressure" treated lumber is not needed because it is not in contact with the ground, however at the very least "treated" lumber should be used.