Having a new deck built with standard pressure treated lumber.
I'll be doing the water seal myself. Do I need to treat the underside of the deck?

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Regards, Ron
USASA 1965/69

If you can seal underside ends all surfaces you will get your best protection.

If you can reach the underside easily I would coat it each time I applied the seal. If the deck is on the ground level then I would pressure wash, let dry, and apply. Just slop it on liberally, no need to smooth out, it will soak in and look good and protect.

There was a product called Superdeck that was supposed to be much better than Thompsons. I don't know if that is still the case or if they have improved Thompsons, but I would research it a little before you buy some. Replacing a deck is not cheap as you already know.

Put it anyplace you can reach, I have used a pump-up sprayer on vertical surfaces and underneath and a roller on horizontal flat surfaces. Ends of boards are critical.
Is it effective? I have my doubts, but no alternative.

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Ipsis Rebus Dictantitbus

Te contractor is recommending that I seal the wood and then paint it after six months. I doubt I'll be painting in the middle of winter, so It'll probably be next spring.
Thanks!

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Regards, Ron
USASA 1965/69

Anything is better than Thompsons. It will wear off after about 2 or 3 rains. Use an oil based stain/sealer like Olympic. I used one with a walnut color. My deck looks way cool! The flat areas need to have a new coat put on about every other year due to foot traffic and direct sun exposure. The uprights still look fine.
Steve

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Steve

Stain it, don't paint it.

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Sure you did

I have had terrific results with a product made by Flood called CWF. It will protect for 3-4 years and returns the wood to a nice honey-brown color. My fence is 16 years old and I re-did it early this summer. Looks better than new. Product lasts longer on a vertical surface, so floors may need to be re-done sooner. It is too thick to spray. I use a roller, then back brush with a 4" brush. Has no odor and equipment cleans up with soap and water. Worth a look.

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Tony

Having been a factory regional manager for both Cabot and Duckback (Superdeck) for the last 15 years --- I'll give you the benefit of my experience.
1st in construction of your new deck the best thing you can do is clean the wood with deck cleaner before staining and stain all 6 sides before installation.
reasons; even though it is 'new' wood you have no idea how long it has layed in a lumberyard or if the wood maufacturer allowed it to cure long enough before shipping. By sealing all 6 sides initally you leave no accessable edge for water or bacteria to wick in.
2) there are 3 types of stain transparent, semi-transparent and soild color. The more pitment in the stain, the longer it lasts. Transparent (3-4 years), semi-transparent (4-5 years), solid (5 years+)
3) darker colors last longer than lighter colors because they have more pignent to fight UV. Clears-- of any type generally last only 1 to 2 years.
4) clean the deck with deck cleaner late fall every year before the snow falls, this will kill all bacteria and mold and give you maximum time between recoating.

Personally I like the superdeck transparent products (1900/2000 series) the best, Sikkens/ Cabot and Superdeck all make a very good quality semi transparent stain of equal good quality and I think Cabot makes the best solid color stain on the market.

As far as Flood goes--- they were bought 2 years ago by Akzo-Nobel and the product made today is not the product made before. The old Flood company of Hudson Ohio made great products, but its gone now.

I would not Use the Thompson's product for anything.

I devoutly used Thompsons YEARLY in a former life over the course of going from a 'brand new deck' to a 'ugly old rotted thing' in less 6 years.

I would recommend the ex's cooking before ever mentioning that product to ANYONE.

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Dum vivimus Vivamas

I'm learning more from this post than I thought I would.
Looks like I'll be looking at alternate treatments. Thanks again.

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Regards, Ron
USASA 1965/69

As others have stated, Thompson's is bad news. I'm not sure what to recommend as an alternative, I have yet to find a retail product that works. Treated lumper needs to "season" a while before you try to seal it. I would suggest that you stay away from stain with high solids or paint. Use either one and you are committing to an annual ritual of pressure washing and refinishing. I used composite decking on the last deck I built, it looked good but it was more costly than treated lumber.

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"Shall not be infringed"

Ron,

I worked for a commercial coatings contractor several years ago and would echo what Buckeyeshooter said.

There are excellent products on the market today, but Thompson's (and now CWF Flood) is not one of them.

As noted, surface preparation is key.

-1 for Thompsons. Doesn't last.

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Misty

+10 for Cabot products!

Are you using pressure treated wood? If so, whatever you do, don't do anything until the wood has dried out a while. If using a clear sealer, four to six weeks will be OK with the newer treating process. If you are painting it, you may need to wait as much as a year. If you don't wait, the paint will peel as the moisture tries to get out of the wood.

Bond Distributing - One TIME WOOD is supposed to last for seven years. It's a little expensive, but much better than sealing your deck every six months with Thompson's. Your time is worth something.

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Insert short witty words here

"...I don't know if that is still the case or if they have improved Thompsons..."

Thompsons has a different version out now in addition to the original formula, put it on the deck a few weeks ago, so will have to wait and see if it is better.

Also place Thompsons on any pressure treated lumber (cut ends and all sides before installing) in a horse trailer floor, and it seems to help the wood resist horse urine and manure better.

Sometime in the distant past I read that pressure treating lumber opens up the pores and grain somewhat, and applying a sealer helps.

I've used an Olympic, semi-transparent stain on my deck twice. It was built out of pressure treated lumber and I let it age about a year before I put the sealer on it. It looks like it should probably be done about every other year. The Olympic has worked great.

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G.P. Charlie

I too vote for Cabot's. Also, you said that you were using PT wood. I recommend that you wait until the wood drys before you seal. I'd wait 6 months to a year before sealing. If the PT you used is anything like the PT available here it is dripping wet with the treating chemicals.

Hawkeye

My original deck on the house I bought in Iowa was all PT wood and it went bad fast even with Thompons. Two years ago I had the PT wood all stripped off and all cedar floors and railings put on. Importantly, all the substructure joists and posts were as good as new after 20 years.

The new wood needs to season/dry for at least a year before you treat with whatever you choose. Rollers and brushes do a much better job than spraying. If you want your deck to look good it will need to be redone regularly.

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Bob.
SWCA 1821

Thanks Bob, I think I'm gonna brush the parts of the deck that are exposed to the sun and use a sprayer for the bottom.

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Regards, Ron
USASA 1965/69

I'll chime in one more time on the wood moisture issue. Ideally you should use a moisture meter and check it before staining. But, I've never been able to get my paint stores or hardware stores to spend the $100 to get one for themselves or customers ( I tell them to rent it out). Ideally the moisture content should be 15% or lower. A higher content will not allow good penetration on the wood. If you take a cup of water and flick large drops on the wood across the deck, you can get an idea of if its ready to stain. If the drops 'bead up' the moisture content is too high, if the penetrate the wood -- its dry enough.
Several folks have mentioned letting it 'age' before staining, this is deceptive. As you can let it age--- however with unsealed edges the wood will still wick mositure over time. Maybe lots more moisture that when it was built depending on where you live and how much rain you get. Aging the wood also can allow it to dry out too much and start to warp. So, you need to be careful there.
If you really want to do the deck and do not want to worry about moisture you can use Cabot SPF. Its transparent and will last about 2 years-- however, it is a waterbourne product designed to be put on wet wood. You use SPF cleaner first, then the SPF. The deck must be wet to apply this product. The moisture allows for the stain to penetrate deeply and displaces the water via osmosis. Then the next restain you can use a heavier pigmented product for longer life.

Don't try to paint treated lumber. Won't work worth mule dukey.

Cabot is my choice. Stay away from Thompson's.
This fence is Cabot cedar transparent after about 18 months


Here's a link to a forum with loads of good info.
Painting - DIY Chatroom - DIY Home Improvement Forum

Ditto on Thompsons! As a well-respected, 62 year old painting contractor told me just today . . . DON'T ever use Thompsons. His statement is use ANYTHING else.

T.

I've used the Cabot SPF on decks before and it turned out pretty well.

I have no experience of the stuff, but a good friend of mine is a painting contractor of 40 years experience, and he curses the Thompson's product. He has favorites (which I cannot recall) but favors anything over the Water Seal.

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Pisgah

I had a Cedar Plank deck in Illinois, lots and lots of square feet, mostly off the ground some second story. I got lots of practice at rebuilding decks. I replaced all of it at least twice, some three times.
I finally ordered all of the USDA wood construction booklets for decks and piers and started building to their recommendations, spaced decking boards, gaps at board ends, supports spaced correct distance from the plank ends, etc. etc. Big improvement.

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Ipsis Rebus Dictantitbus