Pressure-treated wood Corrosion Warnings

[Ryan Grimm]

I was reading the forum topic on roof decks, and someone asked about using Pressure Treated wood for it.

I feel the need to warn people about the increased corrosive action that the new ACQ PT has on steel, even galvy-treated and/or painted stuff.

Simpson Strong-Tie and other building/joist hanger manufacturers are warning about the failure of many galvanized fittings and fasteners used with ACQ, as the corrosive values are about twice as high (IIRC) as the old CCA PT.

I myself have have been called in to do repairs and replacements of deck hardware when the structures failed due to the nails, screws and hangers themselves rusting away.
Many people build with the new ACQ wood nowadays, as it replaces all the old CCA stuff, and are not taking the precautions of using double-hot-dipped galvy or stainless steel fasteners and hangers.

Be warned and aware of this potentially dangerous problem.
It would also be very embarassing to have a deck peel off at highway speeds, tire rubber is scary enough for me whan I ride my motorcycle.

Thanks for reading.

Please check your vehicle if you use PT, and post here with any problems you may find, or just your commentary.
Pull a fastener or two to make sure.

[captainkf]

I had asked about the presure treated wood. Thank you very much for reminding me of that. I had seen somthing about this on a tv show a while back but had totally forgotten.

What about using the "plastic composit" lumber. I have heard great things about it in applications where moisture is a concern. I know it's twice the price and not paintable, but to use as the base that connects the deck surface to the bus seems like it might be a good option. One could do an entire deck possibly.

Just wondering. -Richard

[Ryan Grimm]

Depending on the brand and style of composite decking material, it can be very heavy if it's the cheaper stuff, or very expensive if you want the lighter stuff.

One caveat to stuff like Trex or Timbertech, etc. is weight, and the fact that it sags if left unsupported. It has to be carried (laid) on 2x material on 16 inch centers, IIRC, it's been a couple years since I've used it.
Colors are very limited, as well.

And again, some of it's HEAVY!!! Do you really want to add all that weight to the top of your vehicle?
I'd rather go with 5/4x6 wood decking, if I could afford it I'd go cedar or redwood (light, weather resistant), it would afford drainage in heavy weather, and will add cooling shade in the summer sun.

There are hollow extruded plastic composite decking materials, but again you pay a price for the extrusion process.

You CAN stain Trex and some other deck materials, but if you do so, how do you keep it from getting all over the bus?
And NO synthetic deck material, to my knowledge, is considered to be safe as a structural material, in other words, you can only use it for decking and maybe post/railing material. A structural deck frame has to support it.

I recommend contacting the manufacturers and dealers for more info that's up-to-date on recommended applications and color choices.

Synthetic deck materials have been covered in articles by Fine Homebuilding magazine, The Journal of Light Construction, and many others. Google synthethic decking.
You can also check the resources list of This Old House (pbs.org) for their uses of these products, with an index of suppliers.

BTW, speaking of deck design, how about placing flush tie-down rings on/in the deck, to allow for lashing down loads? Just make sure they're rated for lashing.......

[captainkf]

Thanks for the suggestions. -Richard