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KD vs PT

6K views 6 replies 4 participants last post by  J L 
#1 ·
Thoughts.

I'm building some outdoor patio bench made out of two by fours. Each will be milled down and made square for the box joints.

So here is my question

I can use PT or KD white wood

PT is of course treated for outdoor use but come soaking wet. Making the lead time to build the benches 60-120 days depending on moisture %.

KD white wood come dried but isn't PT.

Both will be painted with a stain and sealer with a 5 year warranty.

So I know PT is preferred but would KD white pine be ok painted for at least several years?

I don't have KD PT in my area.
 
#2 ·
What I normally do with pressure treated is buy the wood a few weeks prior to doing the project and stack it up with sticks between it and allow the wood to dry first. Then it works as well as any wood. Sometimes if you go to a little mom and pop lumber company they will have pressure treated wood that has been there for months and is dry enough to use right away.

Whitewood is going to be very prone to rot. You would have to be especially careful to thoroughly paint the bottoms of the legs to slow this down but it will still rot. Cedar or redwood would be a better wood than whitewood for this however it won't be near as durable as pressure treated.
 
#4 ·
Some boards are going to twist and bend regardless if it KD or PT. It has more to do with the tree and where the boards were cut from that tree than being treated. What gives treated a reputation of bowing is the wood is stacked tightly into a bundle and then put in a pressure treatment tank and saturated with water. Once removed from the tank the wood exposed to the outside dries faster where exposed to air than toward the inside of the bundle and causes the wood to bow. This is why I suggested re-stacking the wood out of bundle with sticks between the boards so air could circulate evenly and allow the wood to dry in a more stable manor.

The lumber companies are starting to wake up and do something about this phenomenon. I haven't seen this in the stores yet but a type wood know as KDAT is being made. The initials stand for Kiln Dried After Treatment which means they pressure threat the wood first and then send it to the dry kiln. This makes the treated wood just as stable and ready to use as the KD wood.
 
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