I've never seen clear all heart TP. Just live with the checking, it's the nature of that kind of wood.

Al

Waiting to finish pt outside lumber has been proven to be completly foolish 10 years ago but still it is repeated.

Al is right its the nature of the material,those treads are going to keep doing what they are doing no matter how they are fastened or what finish is used on them. That is the nature of yellow pine laying flat to the sun.

Less movement can be done,glue up say 3 1/2''rips of ipe with tightbond 111,let them sit in the clamps a few days,cut them to fit,install with construstion adhesive and ss screws counter sink/ filled with tt111/ipe sawdust,sand and do it again. Two or so coats of twp.
J

Many thanks to the two posters who responded. Thanks to them, and some other research I've done I came to the following conclusions :

1) There is definitely discussion about whether it is truly necessary, but leaving pressure treated wood to dry before painting is still common practice. The goal is to allow the chemicals to fully dry. Recommended durations seem to range from 2 weeks to 6 months, with 3-4 months the most common.

2) Some splitting and cracking will occur as it will with any piece of wood this size. Causes include changes in temperature and humidity, etc. Ways to minimize it include careful selection of the individual boards used, and being careful to pre-drill holes, especially if they're within a few inches of the ends of the boards. There was another method in a post above that sounds both very effective, and somewhat complex.

So my contractor was right, or at least following common practise, on all counts. I'm going to ask him to replace a couple of the treads with the worst cracks, and all the new risers he put in to replace the cracked ones - all with pressure treated wood - and we'll delay the painting. I hadn't mentioned it before, but he had to replace the previously installed pressure treated risers as he used the wrong dimension of boards (too small, leaving noticeable gaps), and he tried to use kiln dried wood so as to get our painting done quickly. However, I would rather delay the painting and have more longevity on the structure.

Hope this is of value - R.

Rooster,

anytime that you use 2x pressure treated wood in a visible location, you're gonna be sorry (it's only suitable for a substructure...barely). Do you think the replacement treads will be any better than the originals? they'll split and cup, just like ACQ pressure treated wood always does. You should learn from your own experience.

fool me once, shame on you...fool me twice, shame on me.

steve

The need to fasten the tread in multiple location to each stringer only adds to the shrinkage problem.
PT wood (old and new) is not typically kiln dried after treatment.
It is soaking wet in wood terms.
Checking is further increased by the uncontrolled drying that occurs after installation.
Kiln drying of wood is done under pretty tight controls to prevent excessive checking & warping.
Soaking the wood in water based chemicals comes very close to starting the cycle over again under UNcontrolled conditions.
Either a more resistant type of wood needs to be used so PT is not needed, or you live with the checking of PT wood.
A double 2x6 tread will be a little better.

Thanks for the responses.

Steve, I hear you on the likelihood of repeating the checking on the new treads. I'm gambling that since 10 of the 12 turned out ok (small cracks only) that replacing the two worst will improve things. It may not, or may make it worse - I know I'm rolling the dice and am prepared to take the hit if I guessed wrong.

Brickeyee, you described clearly what the underlying issues are - thank you very much for this. My contractor had suggested the double 2x6 tread but my wife has some say in this and aesthetically it doesn't work. Given the damp atmosphere here in Vancouver, BC, I'm more scared of rot and bugs than checking and warping so we're sticking with PT rather than KD. Had we had more money at the start I would have gone with a cedar porch, but $ ran that decision.

- R.