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Working with treated wood - a few simple questions (I hope)

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Forum topic by BinghamtonEd posted 05-03-2013 01:29 PM 1138 views 0 times favorited 18 replies Add to Favorites Watch
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BinghamtonEd

1453 posts in 1066 days


05-03-2013 01:29 PM

Good morning, all. I have a question regarding wood choice for a project. The project is 2 outdoor gates, one for our deck, and one for the babysitter’s deck, to keep the rugrats imprisoned. To match the decks, I will be using PT wood for each. Since this is something I just want to get done and out of the way, I plan to make a simple frame, joined at the corners using bridal joints, and then screw the ballisters to the outside of the gate (that’s how the ballisters are done on our decks).

Questions -
1.) I’ve done a bit of poking around online, and it looks like a polyurethane glue, like Gorilla glue, would be best for this application due to the moisture content of the wood. Agree/disagree?
2.) Do you think I should be concerned with the wood drying out, shrinking, and the bridal joint coming loose? Wood will be finished with something like Thompsons or Cabot deck stain/sealer.
3.) I plan to counterbore the holes for the screws on the ballisters, and cut some plugs to fit from scrap PT, and glue them in. Sound OK?
4.) Stainless steel fasteners and PT wood play together well, right?

-- - The mightiest oak in the forest is just a little nut that held its ground.


18 replies so far

View crank49's profile

crank49

3466 posts in 1667 days


#1 posted 05-03-2013 02:48 PM

PT wood WILL shrink and twist as it dries out. . . . badly.
Polyurethane glue has very low strength in this application.
i just did a PT fence with it last fall and I can take any board in the fence and just pop it off with a slight twist.
Your bridal joint should be strong enough, if pinned with a large dowel, with or without glue.
Stainless works with PT wood.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

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Tefkar

6 posts in 546 days


#2 posted 05-03-2013 03:00 PM

Stainless is the preferred fastener for ACQ treated wood. Hot-dipped galvanized is acceptable, but will corrode much faster than stainless. Mechanically galvanized is unacceptable. Make sure you use the same alloy for your fasteners and any brackets you intend to fasten with them. So, connect galvanized with galvanized, stainless with stainless, etc.

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BinghamtonEd

1453 posts in 1066 days


#3 posted 05-03-2013 03:06 PM

Maybe I will drive a few screws through the joint as well. I hope it doesn’t twist too bad, I want this gate to still look decent a year or two from now.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View thebigvise's profile

thebigvise

190 posts in 1597 days


#4 posted 05-03-2013 03:08 PM

My choice would be kiln-dried white oak with TB III, stainless steel screws, and perhaps no finish. There is a good article on this subject in the current issue of Fine Woodworking. Go first class on materials.

-- Paul, Clinton, NC

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BinghamtonEd

1453 posts in 1066 days


#5 posted 05-03-2013 03:24 PM

Paul, the big considerations in material selection are matching the existing deck and money. How would kiln-dried white oak stand up to the weather? A few years back we were listed in the top 10 rainiest/cloudiest cities.

-- - The mightiest oak in the forest is just a little nut that held its ground.

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thebigvise

190 posts in 1597 days


#6 posted 05-03-2013 04:08 PM

Well, the author of the aforementioned FWW article on outdoor furniture knows much more than I, so please read his writing on this. My feeling is that outdoor woodwork of any kind is subjected to extraordinarily harsh conditions. The best approach is to accept the fact that your creation will last a much shorter time than, say, a dining room table in doors. But white oak holds up very well outside, and it’s not expensive. I just think that it would be easier to work with than pressure-treated wet, soft pine that will curl and twist and do all sorts of unpleasant things as it dries.

-- Paul, Clinton, NC

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BinghamtonEd

1453 posts in 1066 days


#7 posted 05-03-2013 04:38 PM

Maybe I’ll check out what the lumber yard has for white oak and cedar. I guess, since they’re stained, the difference may be less noticeable. Either one of those options would be exponentially more enjoyable to work and PT wood.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View mnguy's profile

mnguy

162 posts in 2095 days


#8 posted 05-03-2013 05:01 PM

Ed,

I think PT is an acceptable choice, but I could recommend letting it air dry down to ~12% moisture before you do your final milling and assembly. It will warp while it dries, but you can then joint / plane to get straight stock. Not a lot of fun, but I think you’ll get decent results.

I have done an outdoor project in white oak with a simple india ink stain, and it is holding up really well. As long as your gate doesn’t have areas where the water pools and stays wet, and you avoid sap wood, I think white oak will hold up quite well, and it won’t require all the monkeying around that PT will.

I agree with Paul – that FWW article offers good insight (gotta find me some black locust!)

View ChuckC's profile

ChuckC

703 posts in 1632 days


#9 posted 05-03-2013 05:03 PM

I wouldn’t bother with glue. The bridle joint and screws/washers/nuts would be the way to go. If you can, I would recess the bolts into the the wood or use t-nuts so they don’t protrude. If it loosens you can always crank down on the screws.

Don’t pin the bridle joint either.

View Gregn's profile

Gregn

1642 posts in 1680 days


#10 posted 05-03-2013 05:56 PM

What I have done in the past for projects of this nature was to ask if the lumber yard has any pressure treated lumber that has already dried out. Since most of your pieces will be 4’ or less, a lot of times you can find lumber that hasn’t twisted to badly and your able to cut out the straight pieces needed and avoid the drying out and twisting process. You will have to buy more lumber than what is needed, but often times most lumber yards will almost give it away at a really low cost making it and affordable deal.

As for hardware, I have had good luck with galvanized hardware as long as you use fasteners for pressure treated lumber. If your going to glue the joints I would use an epoxy.

-- I don't make mistakes, I have great learning lessons, Greg

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MrFid

550 posts in 601 days


#11 posted 05-03-2013 06:03 PM

Is it spelled “bridal” or “bridle”? We all know what jointing with a bride (or groom) can do to a woodworker.

-- Bailey F - Eastern Mass.

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dhazelton

1221 posts in 993 days


#12 posted 05-03-2013 06:05 PM

I don’t know how large your gate will be but I’d try to add a cross brace of some kind, even if it’s only a turnbuckle and cable. I’ve used liquid nails outdoors with some success. Usually the grain of the wood will separate before the bond does.

View Rick M.'s profile

Rick M.

4204 posts in 1077 days


#13 posted 05-03-2013 07:08 PM

If PT in your area is anything like ours it will be wringing wet, literally. When you drive screws a little puddle of water forms in the hole. So I would buy it well ahead of time and air dry it.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

View oldretiredjim's profile

oldretiredjim

181 posts in 1082 days


#14 posted 05-03-2013 07:20 PM

The big box PT posts I used twisted so bad the cross beams fell out (metal brackets). i have gone exclusively to cedar and redwood for outdoor construction. I had a couple posts twist close to 45*. I had to replace posts for both my gates. The cedar splinters but so does the PT.

View 47phord's profile

47phord

175 posts in 934 days


#15 posted 05-03-2013 07:41 PM

I agree that oak or cedar would be preferable in terms of ease of use, but it will also be 3-4x as expensive as PT. PT usually is very wet when you get it from the yard, but I’ve never had much trouble with warping, though I do try to get the straightest boards I can right from the get-go. I use stainless screws, and to answer your question, I would just skip the glue and use the mechanical fasteners. I also agree with dhazelton on the cross brace idea.

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