deck rebuild question - what to cover joists with ?

[rfuerst911sc]

The deck on the back of our house is structurally sound but the 5/4 deck boards are shot . Previous owner waited way too long to do maintenance so I now have to replace . Have not made up my mind yet on pressure treat vs. composite but that is not my question here . I have read on some forums that some guys are installing some type of " joist covers " to the top of the joists before putting down the decking . I guess the theory is the covers shed water away from the top of the joist so it can just drip on the ground . Kind of makes sense to me . But what are these covers called ? Are they made of thin metal or aluminum or vinyl/PVC or ??? I am picturing something in a 8 ' length that is lightly nailed in place before installing the deck boards . Or maybe a material in a roll ?

I already have good edge flashing where the joists meet the house , I am specifically talking about the tops of the joists . Or is this a total waste of time and $$$ and just get on with R&R ?

[drkshdw]

It's just butyl tape. Search for 'joist tape' to find more but if it's anything like windows, it's not if but when it lets water in, it'll keep the wood wet and accelerate the rotting process.

[Bugsinrugs]

I just recently completed my lower deck and bought 10 rolls of this material
https://www.energyconscious.com/grace-vycor-deck-protector-4-x-75-roll-45639.html?fee=5&fep=3512&gclid=EAIaIQobChMI3IX588-R5AIVsCCtBh2QwQ5LEAQYBCABEgKqlPD_BwE

[Eric 951]

We use 28 GA painted sheet metal (aluminum can be used as well) fabricated in a "U" shape.

[911boost]

+1 to Bugs, Vycor

[URY914]

You can also use rolled roofing under lament (tar paper). Cut it in 6" strips and tack it to the top of the joists then nail the deck planks down. Simple cheap done.

[KFC911]

If it ain't broke...

My 29 yr old original deck and structure is sound.

But I know you....

You won't just replace the deck boards like I would

[island911]

I used annealed copper flashing strips (~4" wide) to top the joists on a deck I built 20 years ago.
Each over-hanging side is folded down maybe 15-30 degrees. This keeps the joists very dry. Whereas any of the wrapped solutions have water running down the joist sides, and clinging.

I've been very happy with my solution. It's aged well.

[rfuerst911sc]

First off thanks for the replies . I am now a little smarter than this morning 😉. The deck is exposed to morning sun then is shaded in the afternoon . The deck is about 10 ' above ground so adequate air flow from underneath . Paul in humid Florida do most builders cover the top of the joists ? The butyl tape or roofing paper once they get wet I would think would promote mold/decay ? KC yeah I over analyze everything !!!

[Zeke]

You could probably nail a copper wire along the top of each joist. Copper and fungus don't exist.

[Amail]

Originally Posted by Zeke

You could probably nail a copper wire along the top of each joist. Copper and fungus don't exist.

Copper and fungus; just like unicorns.

[URY914]

Rick,

In Florida most builders go the cheapest and fastest method possible and unless the owner tells them to put something on the top of the joists they won't do it. It's all about keeping the first cost of the house as low as possible and let the next guy pay for replacing the deck.

[KFC911]

When I pull deck boards up, and I have pulled up every nail that rears it's head...replaced with 3" deck screws....the nails are tough to extract and my sub-deck has nothing but solid structure. Don't you have an attic to insulate in Aug instead ?

Do something extra....only if'n ya need to....

Lay Z Boy

[MBAtarga]

I've never heard of this being done - although I do understand what it is trying to avoid.

[Bugsinrugs]

In my county covering the deck joists is required by code. Also, all joists must be pressure treated.

[Zeke]

Originally Posted by Amail

Copper and fungus; just like unicorns.

OK, there are the exceptions. Do they exist freely in nature? Does this same wood degradation reasonably affect PT deck joists?

Apparently Island911 believes copper in the extreme does. Or is his copper non reactive and could be substituted with any wrap-over covering?

I admit I jumped in too soon with my comment and after your response I delved in. W/o citing a bunch of studies involving micronized copper and nanoparticles, I think the idea of a copper strip is even more effective chemically speaking than a copper cover because the strip will leach into the edge of the joist whereas a cover is going to be in place mainly for it's longevity. Water in his case is apparently not intended to soak into the wood but rather be expelled.

I take my theory from the roofing business where copper and zinc are used to mitigate lichen by killing the fungal side of the complex structure.

Amial, me thinks you know a whole lot more than I ever will, but tell me, is a copper wire on top of a joist exposed to moisture a complete waste of time and material? Tell me if it has no redeemable value or let it go.

[drcoastline]

If the deck is properly pitched and you have adequate airflow, don't see why you would need anything? Which appears to be the case? Not sure how old the deck is but, if it lasted this long and you say is in good shape, then I would say just put down new deck boards.

[Amail]

Originally Posted by Zeke

OK, there are the exceptions. Do they exist freely in nature? Does this same wood degradation reasonably affect PT deck joists?

Apparently Island911 believes copper in the extreme does. Or is his copper non reactive and could be substituted with any wrap-over covering?

I admit I jumped in too soon with my comment and after your response I delved in. W/o citing a bunch of studies involving micronized copper and nanoparticles, I think the idea of a copper strip is even more effective chemically speaking than a copper cover because the strip will leach into the edge of the joist whereas a cover is going to be in place mainly for it's longevity. Water in his case is apparently not intended to soak into the wood but rather be expelled.

I take my theory from the roofing business where copper and zinc are used to mitigate lichen by killing the fungal side of the complex structure.

Amial, me thinks you know a whole lot more than I ever will, but tell me, is a copper wire on top of a joist exposed to moisture a complete waste of time and material? Tell me if it has no redeemable value or let it go.

Zeke, buddy, you misunderstand me - I was just poking fun at your choice of words. I think you meant to say "copper and fungus don't co-exist". I'd lay odds you know more than I ever will!

[island911]

Originally Posted by drcoastline

If the deck is properly pitched and you have adequate airflow, don't see why you would need anything? Which appears to be the case? Not sure how old the deck is but, if it lasted this long and you say is in good shape, then I would say just put down new deck boards.

The thing is, the same conditions that took out the decking are there, on the joists, exposed in the deck spacing. Even treated joists look nasty at every gap.

Capping the joists is doing your future self a big favor; assuming your not a flipper.

I like the copper for a few reasons. First, as Milt sez not much grows in contact with copper, Second, annealed copper is very easy to work with. (Al flashing is typically cold rolled) Third, copper patina is dark(fades away) whereas Alum is shiny.

[rfuerst911sc]

Originally Posted by drcoastline

If the deck is properly pitched and you have adequate airflow, don't see why you would need anything? Which appears to be the case? Not sure how old the deck is but, if it lasted this long and you say is in good shape, then I would say just put down new deck boards.

Good point , I can only assume the deck was built in 1996 or later as the house was built in 1996 .