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First Project- Should I have used PT? I used Douglas Fir.

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Forum topic by kenbass4 posted 877 days ago 1195 views 0 times favorited 16 replies Add to Favorites Watch
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kenbass4

5 posts in 877 days


877 days ago

Ok, I built this using Douglas Fir. I keep going back and forth…should I have built it with PT? I need some piece of mind because Im driving myself crazy. How long will this last if I keep it treated? What should I use to treat it? I was thinkin about wrapping the bottoms with tyvek or tar paper to protect from moisture. Thoughts?

there are 2 swings on this now. I want to add a deck and slide to this at the end of the summer or next year.


16 replies so far

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thebicyclecafe

23 posts in 883 days


#1 posted 877 days ago

Douglas fir can stand up to mouisture quite well- so for the most part the studs should hold up quite well. However it’s not rot resistant, so where the studs touch the ground are of concern. At this point, maybe you can just try your best to encase the bottoms with latex paint, or seal it with a thick layer of polyurethane?

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brtech

664 posts in 1556 days


#2 posted 877 days ago

There is no black and white answer.

PT will last longer

Some of us worry about kids and chemical contact with the PT treatment. The newer stuff is better than the old stuff.

Dunno if tyvek or tar paper will do anything for you. I’d probably just build up a good exterior finish poly with some UV inhibitor in it and renew it every year. One idea that I saw in another thread for this is to get clear base paint (no tint). It has loads of good stuff and dries clear. Weird to get, but very cost effective.

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kenbass4

5 posts in 877 days


#3 posted 877 days ago

Thanks for the tips. How long would you expect DF to last if I maintain a good Poly with UC inhibitor? Roughly?

View Jeff in Huntersville's profile

Jeff in Huntersville

399 posts in 1828 days


#4 posted 877 days ago

In my experience your kids will grow out of it before the studs rot.

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kenbass4

5 posts in 877 days


#5 posted 877 days ago

phew…that makes me feel better. Everyone keeps saying i should have used PT.

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BlankMan

1487 posts in 1986 days


#6 posted 877 days ago

No matter how safe they say PT is I don’t know that I’d use it for something kids may be climbing on. I don’t even use it for my raised gardens that I grow vegetables in, I use cedar for those.

Depending where you are located you may not want to use polyurethane. Large temperature and humidity swings could cause it to crack, it’s not flexible enough. I built a bird feeder probably 10 years ago now, been outside ever since, the pine is still yellow, shows no signs of weathering. I sealed it with Spar Urethane, it’s more flexible then polyurethane and seems to have done a good job. Haven’t put another coat on since it’s been out there in our Wisconsin winters.

-- -Curt, Milwaukee, WI

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Mainiac Matt

3898 posts in 962 days


#7 posted 877 days ago

As mentioned, the new ACQ PT (which is all you’ll find for retail sale) is much safer than the older CCA PT(copper, chrome, ARSENIC)... Of course the CCA preserves much better, as evidenced by it’s continued use for marina pilings, and other industrial projects.

None the less, I wouldn’t use either one on something that little kids play on, as they often can’t keep their hands out of their mouths.

If you’re really worried about it, dig a 12” diameter hole about 6” – 12” deep at the location of each post and fill them up with 3/4” washed stone (the kind they use in septic tank leach fields). That will keep the feet from being in contact with wet soil all the time and go a long ways to extend the life of the timbers.

-- Pine is fine, but Oak's no joke!

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bondogaposis

2493 posts in 985 days


#8 posted 877 days ago

Your kid will outgrow that little toddler seat much faster than DF will rot. Also PT lumber isn’t the best structurally due to knots etc. You did good.

-- Bondo Gaposis

View Mainiac Matt 's profile

Mainiac Matt

3898 posts in 962 days


#9 posted 877 days ago

if you feel that you must treat it with something…. let it whether for a few months b4 doing so.

-- Pine is fine, but Oak's no joke!

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WDHLT15

1100 posts in 1109 days


#10 posted 877 days ago

Get the feet out of the dirt. The washed stone like ssnvet says is good or set them on some concrete pavers.

-- Danny Located in Perry, GA. Forester. Wood-Mizer LT15 Sawmill. Nyle L53 Dehumidification Kiln

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oluf

256 posts in 1673 days


#11 posted 877 days ago

Cut the tops off of four gallon milk bottles. Set the legs in the bottles and fill them with quickrete. They won’t rot off.

-- Nils, So. Central MI. Wood is honest.Take the effort to understand what it has to tell you before you try to change it.

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TopamaxSurvivor

14726 posts in 2309 days


#12 posted 876 days ago

Get the feet out of the dirt and keep them up where moisture will drain away from them. Either paint or use high quality 99% UV protection like Log On and it will last long enough for the kids to out grow it ;-)

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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felkadelic

193 posts in 1173 days


#13 posted 876 days ago

There was an article in one of my magazines (I think it was WOOD) that discussed using an epoxy to seal the areas where the wood would contact moisture from the ground. Might be worth looking into—let me know if you’d like me to try to find the issue number.

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tomd

1750 posts in 2404 days


#14 posted 876 days ago

Cut four small squares out of PT wood and screw to bottom of legs this will keep it off the gound and will not rot, also I would just paint the rest.

-- Tom D

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doughan

96 posts in 1225 days


#15 posted 876 days ago

what ssnvet said …..sealing the ends won’t do much to the rate of rot but speed it up…...it will still get wet and the sealer will hold the moisture in as well.

ask restoration carpenter what happens to fir beams that are painted.the paint wearout on top before the side and bottom allowing moisture in and then it won’t dry because of the paint.wet wood rots faster.
set it on rock and seal the whole piece of wood or don’t seal at all.sealing just the bottom and a little up the sides would be like wrapping it in a plastic bag.once the water is in it will stay

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