Subscribe or Renew Membership Subscribe Renew

Must one use pt wood for framing a deck?

Howard_G_Page's picture

*
My contractor started building our deck and is not using
pt wood for the framing. He claims it is unnecessery
here in the California Bay area (near San Francisco).

I would guess one should at least use pt wood for the board
that is bolted to the house.

Any opinions in this matter are greatly appreciated. Thanks.

(post #170326, reply #1 of 14)

*
I live in the east bay hills. Unless you do not care about rot, you should use pt wood or redwood which is naturally rot and insect resistant.

(post #170326, reply #2 of 14)

*
Howard. PPT wood is guaranteed against insect infestation. PT wood is not immune to ultraviolet degradation,or moisture damage. The ledger board bolted to the house must be carefully flashed to keep water from penetrating by capillary suction between the PT board and the house.

(post #170326, reply #3 of 14)

*
Howard, I don't know how things are done in CA., but here in TN if I built a deck out of standard framing lumber I would be completely rebuilding it in a year. Moisture has the same damaging effects on nonweather resistant anywhere in the country. As a licensed contractor I suggest that in light of this severe lapse in judgement of your builder, you also have the rest of your house inspected by a qualified third party.

(post #170326, reply #4 of 14)

*
I agree with Michael. You should use PT wood, Redwood, or Cedar. Standard Construction Grade Fir just won't cut it. For outdoor wood which will not be subject to direct sun or water, you can get away with douglas fir. But I assume your deck is not covered, and that water will reach the joists.

This guy must be low bid. Since most of the expense of the deck will be labor, please re-consider, and have this done properly, unless you are moving soon. Good Luck

(post #170326, reply #5 of 14)

*
Hey call me a hack but I just completed two decks that were framed with Hem/Fir joists that were treated with a couple of spray coats of Olympic sealer. The ground level deck is off the ground at least 12" and supported by PT 6x posts on concrete posts with footers. Decked with 2x6 RW and has a roof, faces E/SE. The upper deck is also framed with Hem/Fir and is approx. 9' off the ground and is uncovered and decked with 2x6 RW. I live at elevation in Colorado and decks that I have done 10 years ago here the same way are in great shape. Any wood that is in contact with cement/concrete should be PT or RW. Any wood in contact with the ground should be made so it is not in contact with the ground! Use galvie fasteners for exterior.

In other words if it works in your area, go with it. Your building inspector should be able to tell you if your contractor is doing you right, give him a call.

(post #170326, reply #6 of 14)

*
Hey call me a hack but I just completed two decks that were framed with Hem/Fir joists that were treated with a couple of spray coats of Olympic sealer. The ground level deck is off the ground at least 12" and supported by PT 6x posts on concrete posts with footers. Decked with 2x6 RW and has a roof, faces E/SE. The upper deck is also framed with Hem/Fir and is approx. 9' off the ground and is uncovered and decked with 2x6 RW. All connections to the building are flashed to prevent water going behing the rim at the house. I live at elevation in Colorado and decks that I have done 10 years ago here the same way are in great shape. Any wood that is in contact with cement/concrete should be PT or RW. Any wood in contact with the ground should be made so it is not in contact with the ground! Use galvie fasteners for exterior.

In other words if it works in your area, go with it. Your building inspector should be able to tell you if your contractor is doing you right, give him a call.

(post #170326, reply #7 of 14)

*
Folks -

We just sold a house in the NorthWet (Bellevue, WA) that had a deck made of cedar, about 20 years old - and it was going, going... We just kept chasing rot from one 2x4 to another. (How I Spent My Summer Vacation.) It had a fir and hemlock a few feet away and a constant rain of needles. I was surprised it lasted as well as it did.

I think design has a lot to contribute to deck rot. Where does the water and the debris wind up.

The materials were fine, but this deck had 16d. board spacing and butt joints. Both too tight. The needles that rained down could not fall through, but could collect and trap moisture between adjacent 2x4s and work on the ends at the butt joints. It was getting down into the supporting joists.

BTW - the fastners were 16d hot dip galv. finish nails and they were in great shape after all those years. I've used electroplated on shed roofs. Bad Career Move. You get about 6 months, not 20 years out of them.

If I had to rebuild that deck, the spacing would be far more open, the whole thing would be PT wood, back primed, ends dipped, double joists to allow space in butt joints rather than having to break on one joist, and 15# felt strips laid over the joists to divert a bit of water (might help, can't be worse than what was happening down there, out of sight). There were some interesting pockets of rot getting into the joists.

J Wells

With the new recipes for PT (post #170326, reply #14 of 14)

With the new recipes for PT (ACQ), you should also use stainless steel nails/screws/bolts, or some of the new coated screws guaranteed for use with any kind of PT wood. The higher copper content of the non-arsenic pressure-treating formulas is said to eat up galvanized fasteners--even hot-dipped.

 

============

". . . and only the stump, or fishy part of him remained."

PreviewAttachmentSize
P4038644crw1.jpg
P4038644crw1.jpg285.3 KB
P4038643crw1.jpg
P4038643crw1.jpg249.06 KB

(post #170326, reply #9 of 14)

*
Howdy neighbor. You've got some good advice and now here's my experience: I've seen a lot of old decks over here in Marin built before the widespread use of PT lumber and the framing has always been the part that fails first. No matter how well built, certain points are subject to moisture and rot. Once a weakness is created, bugs move in fast and then move on to the rest of the wood. Our climate is perfect for termites, beetles and carpenter ants. I hate to promote toxics, but I highly recommend using PT to lengthen the life of your deck, especially at the ledger and areas that cannot be accessed later. If it's too late, careful application of a preservative will help if repeated every few years.

(post #170326, reply #10 of 14)

*
Everybody: Thanks for your thoughtful replies.

I convinced the contractor to replace the
board bolted to the side of the house (ledgar board?) with a pt one.

(post #170326, reply #11 of 14)

*
My contractor started building our deck and is not using
pt wood for the framing. He claims it is unnecessery
here in the California Bay area (near San Francisco).

I would guess one should at least use pt wood for the board
that is bolted to the house.

Any opinions in this matter are greatly appreciated. Thanks.

PT wood (post #170326, reply #12 of 14)

I would greatly recommend he use pt wood. I myself am a deck builder and by experience I can say that all these contractor decks start falling apart in about 3 years. Especially if the screws and nails aren't galvanized or stainless steel. And for the ledger bolted to the house like it was metionned in a previous post, it is important to add a piece of flashing to cover it even if its pt wood

Patio Deck design ideas www.patiodeckart.ca

Max (post #170326, reply #13 of 14)

welcome to Breaktime. 

Eventho the post you replied to is close to 15 yrs old, I hope you'll stick around and add your expertise to the discussions. 

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


(post #170326, reply #8 of 14)

*
The short answer to you question is NO; it is not a "must".

Regrettably, the question is "should" and the answer to that is YES.

Decks I've built in Northern CA do not require PT for non-soil contact. (need a 6" standoff to soil). Also, I see lots of decks on the little concrete piers sold at HD directly on soil. These are not adequate without a poured footing underneath.

A previous response suggests asking the inspector, which is good to find out what the local code is, but beware: Inspectors are woefully inadequate in guiding you to building a quality project. Lots of junk gets inspected.

Keep in mind that there are different grades of PT. The native lumber used will dictate your strength, affecting sizing and spans. Hem Fir is inferior to Doug Fir. (RW is also not as strong as Doug Fir, and to complicate matters, much RW is sold ungraded ie "all red", etc)

The pressure treating process also differs. If I am going to the expense, I use 0.40 PCF, which is a measure of the percentage of the preservative remaining in the wood. The typical varieties are 0.25PCF I believe.

Remember, rot starts on the ends, and when you cut a piece this leaves the end grain totally unprotected. If practical, I'll sit the end grain in a pan to let it pick up preservative (like the Green Copper stuff). Tedious stuff

BTW, just built a 1300 sqft deck with TREX, using the Deckmaster brackets...tricked out design, lots of angles and not a single nail/screw head. Looks great, and expect it'll last 20 years.