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AdamsHouseCat 02-22-2012 08:02 AM

Restoring old deck using old Joists
I have a relly old treated pine deck. The surface boards were beyond any restoration, and I have removed them. The rafters underneath are in pretty good shape. There are some signs of aging on the rafters where the cracks were between the surface boards.

To extend the life of the rafters as long as possible, I plan to pressure wash and spray Thompsons water seal on these old rafters.

I am a little bit concerned about the top surface of the rafters - (the exisiting weathering, the nail holes and pry bar marks) and wonder if I should "top coat" the rafters with some flat black exterior paint, or maybe even that "Deck Restore" gritty paint product.

Any thoughts for me on this?

Thank you very much!

joecaption 02-22-2012 08:14 AM

Without a picture it's hard to say.
Thompsons comes out time and time again the poorest rated wood treatment in Consumers Digest.
Use Cabots or Olymipc solid stain instead, better yet use a wood preserver.
I've seen where somepeople staple tar paper over the top of the joist to deflect the water away.
(PS there called joist not rafters. Rafters are what's holding up your roof.)
When you install your new boards use ceramic coated screws not nails. Far less likly to pull out and will not rust off.

Daniel Holzman 02-22-2012 08:47 AM

Assuming your joists are in reasonable shape, you should consider installing a waterproof barrier above the joists. This could be Blue Skin (TM) or ice and water shield (that is what I used). For ice and water shield, you cut strips that are about twice as wide as the joist, and the length of the joist, then simply apply it to the top of the joist. I saw this technique in Fine Homebuilding magazine, and others on this site have used it. Said to prolong the life of the joists from 20 years to up to 40 years.

titanoman 02-22-2012 09:08 AM

Flip the joists upside down for a fresh nailing surface.
These "rafters" should be treated lumber if they're not already.

CaptRandy 02-22-2012 01:28 PM

Pressure wash using a brightener to kill mold and mildew. Allow to dry then coat with Ready Seal. Do not put any type barrier coating it will collect water on top and rot your new boards from the bottom up.

titanoman 02-22-2012 02:01 PM


Originally Posted by CaptRandy
Pressure wash using a brightener to kill mold and mildew. Allow to dry then coat with Ready Seal. Do not put any type barrier coating it will collect water on top and rot your new boards from the bottom up.

So will the old holes.
That's also why I said flip them over.

CaptRandy 02-22-2012 03:34 PM

Hove no problem with flipping, do it often with deck boards as well.

Done That 02-23-2012 07:11 AM

Another vote for ice & water or similar like Grace deck protector which just costs a bit more because it's already cut to width. Seals around the screws you drive for the new top boards. I used it and was easy and I think well worth the minimal extra cost on a new deck project.

user1007 02-23-2012 07:17 AM

Thompson's is total marketing hype and you should not use it on anything. It is a liquid wax based product and you will be lucky to get a season out of it. It does not penetrate wood fiber like a good sealer will. And it is dramatically overpriced for what it is.

CDragon 10-21-2012 12:50 AM

Can anyone point me to a long-term study or any kind of evidence that sealing the tops of joists extends the longevity of joists? Where did the "Said to prolong the life of the joists from 20 years to up to 40 years" figure come from? I've been searching off and on for three days and while a lot of membrane-selling sites and contractors say they sell their customers on adding various "self sealing membranes" above the joists, I can find absolutely no proof that it helps. In fact, the only shred of long-term evidence I've been able to find is one person who said "I've replaced decking on older deck done both way, not sure why but the ones with tar paper or storm and ice shield were more rotted then the ones left exposed."

Now, of course, tar paper isn't necessarily self-sealing, but storm and ice shield should be. More importantly, I take what he said as evidence that if water ever gets under the "water proof" membrane, it will not dry out and rot will be greatly accelerated. So even if the self-sealing membrane works for 5 or even 10 years to keep it dry beneath, if it ever fails then rot is accelerated and the beam will probably not last any longer than if no membrane had been present - it might even fail faster than without a membrane. And it's very hard for me to believe that a membrane is going to completely stop water for 40 years. Those screw holes are going to start letting water pass at some point due to UV exposure, freeze/thaw, shifting boards due to weather/humidity changes/wind/earthquake/whatever, or even if someone removes a screw and drives it back in without hitting the same hole in the membrane (will a membrane hole missing a screw completely self-seal? I doubt it). It seems almost inevitable to me that at some point the membrane will accelerate rot instead of stop it.


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