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Question DetailsAsked on 1/13/2014

building new deck, use composite or K-dat/pressure treated wood. Saw many complaints on fading and mold/mildew?

saw law suits for Timber Tech,Aztech,etc & reccalls on composite too?

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I have seen enough problems with composites that I recommend against all of them. The pure plastic products are longer lived, but have the usual problems with plastics exposed to sun as vinyl wondows have - warping, cracking and "grain" lifting, fading, softening of the surface, and scaling and peeling of paint.

My recommendation for decks is ground-contact rated ACA/CCA/ACCA/ACQ family copper chromate or copper napthalate or napthenate treated wood (the green all weather wood). In my experience, the brown "Wolmanized" treatment is useless - I have seen it start rotting in a couple of years, and leave it laying on the ground or even in stacks in a lumber yard and the protected side will start fungusing in short order. ACQ is better but not as heavy a dose, so appears to be much shorter lived protection, though it can be recoated with copper napthenate solution to rejuvenate the protection. Unfortunately, they have eliminated the last "A" in the listing for residentiall use - the arsenic, which really made this wood insect proof, so now many brands are proving less than proof against high-determination breeds of carpenter ants and termites and boring centipedes - found a termite nest bored inside a large bundle of new treated timber at the lumber yard a few months ago, apparently infested at its manufacturing location and shipped in, since we do not have termites where I live. They had bored right through a foot or more of treated wood to get to the center where the nest was. The copper and chromium compounds protect against fungus and mold and bacteria growth. In addition, all the product I have seen in the last 5 years or so has had very poor penetration - probably because they are mostly using a water based solution rather than natural gas carried - get the natural gas solvent type is at all possible. The water based is a joke - makes absolutely no sense if you think about it, because not only does it swell the grain thereby limiting the very penetration you want, but wood cells also filter out the chemicals from the water, so only the water does most of the penetrating to depth, which does not happen with the oil based, therefore leaving the core susceptibel to decay and insects. It used to be a 2x piece would have full penetration to the very core of the piece - now you cut it and you see maybe 30-40% penetration, so I recoat everything I use before installation (after a couple days ddrying if the bundle is wet). Posts going in the ground I thoroughly soak with a paintbrush or roller twice all around (with at least two drying days in between or it will be sticky for a long time), plus of course heavily coat cut ends with the treatment solution. Deck boards you do NOT want to do 2 coats back to back as it can stay sticky for weeks - but a good thorough soaking recoat AFTER being cut to length, with a wipeoff after 1 minute or so soak time, helps a great deal.

IF you do the recoat on timber to be used in the house framing - bottom plates, door sill door plates, etc - you have to either not recoat it or have a stockpile to draw from that has aged for months, otherwise you will get objectionable odors in the house.

Treated timber has to thoroughly cure before any staining or painting, so I recommend a minimum of 30 and referably 60 days weathering after the bundle is opened up (and recoated, if doing that), and must be totally dry before staining or painting to ensure penetration. Use only oil based products because latex will come off due to the oil based penetrant. Stains obviously have to be either green or dark brown or black or red (which turns brownish) to work on the green wood, and of course test first - the green penetrant can alter the stain color significantly. If desired, after testing or color, you can colorize the treatment being used for recoat itself - you can also buy it in deep brown. For paints, where the customer insists on paint, I have recommended 10% thinned oil based garage floor and deck paint - I have one 30 year old deck where it was painted with 2 coats of oil-based Sears Weatherbeater Garage Floor and Deck paint after installation, and it and a neighbor's 15 year old deck are still looking good (though not glossy any more), with no peeling or blistering.

Generally, paints are a bad idea, because they invariably get nicks and holes in the paint "hide" so water gets under the paint and readily wicks into the wood, but then cannot evaporate because the holes or cracks are too small to allow effective evaporation. Penetrant you can and should coat all surfaces. Heavy-bodied stains and paints you should never paint the non-exposed side (house side on siding, bottom side on deck boards), to leave an open uncoated surface for evaporation. I also do not recommend painting supporting members at all - just the copper treatment.

If a sealer is used, again use a thin, very liquid mineral spirits based one that will soakk in, rather than make a solid coating on the surface which traps water and can peel and blister.

Answered 6 years ago by LCD

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