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Protecting deck joists from rot

pjbaum | Posted in Construction Techniques on September 4, 2006 01:38am

Getting ready to replace deck due to rot in the joists.  In the past I have used Woodlife sprayed between every plank to protect the joists.  What is the best way to protect joists?  Have been told to use aluminum strips between planks and joists or tar paper.  Reports indicate the aluminum corrodes in contact with treated wood and tar paper loses tar in our Seattle climate.  Inclined to use Timbertech Floorizon planks that only contact joists in three spots and also are tongue and groove to minimize moisture contact and provide air circulation.


Edited 9/20/2006 5:40 pm by pjbaum

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Replies

  1. plumbbill | Sep 04, 2006 02:42am | #1

    Ice & snow sheild¯

    seems to be the weapon of choice these days.

    Seattle climate------ Oh c'mon we only have 2 seasons--------- warm rain & cold rain.

    "I'm here to chew bubble gum & kick azz, & I'm all out of bubble gum" Rowdy Roddy Piper

  2. User avater
    NickNukeEm | Sep 04, 2006 02:45am | #2

    Grace Vycor deck protector:

    http://www.graceathome.com/pages/deckingprod.htm#DECK_PROTECT

     

    "I am the master of my fate, I am the captain of my soul."  Invictus, by Henley.

  3. Piffin | Sep 04, 2006 02:49am | #3

    Vycor, but don't use real wood for decking then. the vycor will protect the framing but keep the decking wet on bottom side and rot it within ten years heree, maybe five out there.

     

     

    Welcome to the
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    Knowledge FHB Campus at Breaktime.
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    1. calvin | Sep 04, 2006 04:06am | #4

       and rot it within ten years heree, maybe five out there.

      Lets see, how is it put respectfully.  I don't agree, what is your reasoning and what proof do you have?

      thanks paul.

       A great place for Information, Comraderie, and a sucker punch.

      Remodeling Contractor just outside the Glass City.

      Quittin' Time

       

      1. Piffin | Sep 04, 2006 04:29am | #5

        Proof - the ones I have torn up that were only ten years old with tarpaper protecting the joists.
        Since it is wetter and warmer out in Oregon, I presume it'll take less time out there 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. calvin | Sep 04, 2006 04:37am | #6

          You think the vykor would do the same thing as the paper?

          What about retention of moisture with bare wood joists?A great place for Information, Comraderie, and a sucker punch.

          Remodeling Contractor just outside the Glass City.

          Quittin' Time

           

          1. Piffin | Sep 04, 2006 05:01am | #7

            The vycor is more waterproof than tarpaper, so I can only assume that it would keep the decking in contact with it wetter.all the old decks around here that had been built with spruce or hemlock framing had the tarpaper. Where it was under cover of a roof, it was fine for both decking and framing. Where good antique heart pine had been used in the 1890s, it lasted forty years or so, reportedly. but then it got replaced with CVG doug fir and it then had to be replaced every ten to fifteen years when out in the open. The last tweny years we've been doing them with PT framing. and no taarpaper. I went to IPE decking about eight years ago. we'll have to see about it.note - I have some good old frame 2x10s and 2x12 that had been decked three and four times ( count the nails, some old original cut nails) that I still use for staging planks salvaged from old decks built a hundred years ago. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          2. Piffin | Sep 04, 2006 05:05am | #8

            I'm thinking "why would Cal not believe this?"Well, I think because his experience is different than mine...why would that be? Either you use a differeent wood for decking that is more rot resistant, or you paint or treat the decks better, or your climate is drier there. I know that overall the climate is drier in much of Ohio, but you are right down by the river and fog, right?We have maybe 30-40 dry fog free days a year here. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          3. calvin | Sep 04, 2006 05:13am | #10

            Most of the porches of any age were fir.  There was a period of RW decking.  Now, either composite or PT. 

            The only rot I've seen in reno's was the tops or ends of joists (much of it local milled) and the bottom or ends of the fir T&G. 

            Where we are here, things can dry out.  The river/fog/moisture is minimal.  Dark, undrained and usually misdirected sprinklers cause problems.  Contained by bushes etc with no air movement.

            Other than that, poor maintainance-lack of paint, gutter damage, too high with grade.A great place for Information, Comraderie, and a sucker punch.

            Remodeling Contractor just outside the Glass City.

            Quittin' Time

             

          4. Piffin | Sep 04, 2006 05:21am | #11

            Yeah, it's the bottoms of the decking I'm talking about, where it stays wet from constant contact with the tarpaper. The tops will look fine, but it gets to where when you walk on it, there is soft compression over the joist and the nails start to trip people. Or you get called to fix one piece of decking and when you take it up, you see it is rotted half way up from bottom at joists. Then discover same on whole deck, tyhough they can get by fora couple years if they want too.One deck I did with PT frame no tarpaper and fir decking in '88 or 89 was just starting to go bad three years ago, last i saw it. The so-called 'caretaker' used Thompsons on it three times in all those years. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          5. calvin | Sep 04, 2006 05:27am | #12

            It's the bottom of the decking......

            Yes.  Here I have seen no paper of any kind on the old construction and really don't think i'd see any vykor.  When I first read about it, it was meant to protect the connection of the deck to joist-effectively taking care of the joist damage I had seen before.  I just don't know if I can put my brain around the difference of vykor or nothing.  Both a pretty tite connection of deck to joist, one repelling water, one not, other than draining.

            But I promise to remember this discussion if I ever get a call to do a deck up there

            on an island.A great place for Information, Comraderie, and a sucker punch.

            Remodeling Contractor just outside the Glass City.

            Quittin' Time

             

          6. davidmeiland | Sep 04, 2006 08:43am | #13

            So your thinking is that the felt/Vycor is holding more moisture under the decking than bare joists would. My instinct is to think the opposite, that without flashing the tops of the joists would hold more moisture and keep the bottom of the decking wetter. I haven't stripped a deck with flashing on the joists, so I don't know. Most of the older decks here are nailed down and get fairly loose, so the decking is not always in much contact with the joists anyway, so I think they dry reasonably well.

            I've installed ipe decking over Vycor over 2x PT joists, and the screws suck the decking down quite tightly, compressing the Vycor enough so that I think little water gets under there. Time will tell, I suppose. It's common practice out here to flash joists. I recently saw a product advertised somewhere that's a plastic C-channel to be used for joist flashing.

            edit: I think felt would be worse for flashing than Vycor as it gradually absorbs moisture. Used horizontally it would not be ideal.

            Edited 9/4/2006 1:45 am by davidmeiland

          7. Piffin | Sep 04, 2006 05:34pm | #16

            When a piece of deckingcan dry in 360°, it will, but when vycor stops it from drying at that point, the wood stays wet there for several days after a rain. When the connection is wood to wood, the joist can help wick it away.I don't see any need for tarpaper or vycor when the joists are PT. It is impregnated with chemical to protect it from rot. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          8. User avater
            xxPaulCPxx | Sep 07, 2006 05:59am | #27

            OK, here is another idea:

            Instead of adding a new material - like my cut timing belts for instance - why no just slightly round or angle the top of the joist?  A single pass with a router or a circular saw would do it:

            View Image

            In this illustration I put two angles on it, but you really only need one that goes all the way across.  Instead of bearing on a flat face, it would bear on an edge.  There would always be an air space except for a very tiny portion where the plank bears on the joist.  A membrane would still be used on the joist, of course.  If the cuts were light enough, you wouldn't get below the treated wood... and that would be under a membrane anyway.Rebuilding my home in Cypress, CA

            Also a CRX fanatic!

          9. Piffin | Sep 07, 2006 06:11am | #29

            We just can't keep you inside the box!LOLit would have to be beveled to both sides - because with one angle taken off only, the load would be directed all on one side of the joist and the stresses would make it want to twistBut other than the time it would take to work them up that way, I like it. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        2. Notchman | Sep 04, 2006 05:23pm | #15

          I haven't watched much news lately, but last I checked, Seattle is still in Washington.  :-)

          BTW, PNW weather.....wet in winter, dry in summer.  No rain here in nearly 2 months...typically we won't get much 'till late October.

          1. Piffin | Sep 04, 2006 05:35pm | #17

            Thanks for the corrective Geography lesson!;) 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

    2. User avater
      xxPaulCPxx | Sep 05, 2006 08:27pm | #19

      This is something I was thinking about regading the problem of moisture on the underside of deck planks. 

      Automotive timing belts are hard rubber and have one side with grooves the go perpendicular to the direction of the belt - rubber teeth to catch on the cams.

      If a belt is cut and laid along a joist, over the press on water barrier, with the rubber teeth pointed up, you have an inch wide rain screen that is solid enough to take the weight without significant movement (no squish).  See my illustration below:

      View Image

      Now air can move freely under each plank, keeping the joists dry.Rebuilding my home in Cypress, CA

      Also a CRX fanatic!

      1. Piffin | Sep 05, 2006 09:29pm | #21

        Not a bad idea!But where would you go to buy that much belt?
        Or
        How well do you get along with junkyard dogs? 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. User avater
          xxPaulCPxx | Sep 05, 2006 10:35pm | #22

          Yeah, no question going to the autoparts store and buying a gross of timing belts to cut up might be a bit steep!  A quick eyeball on a parts site and measuring the one on my CRX breaks down to $6 per ft. There's got to be something out there that might be similar though.

          Rebuilding my home in Cypress, CA

          Also a CRX fanatic!

          BTW, when you are a CRX fanatic, you get to know Pick-A-Part junkyards very well.  People throw away perfectly good CRX's all the time... some have only 200,000 miles on the odometer!  What a waste.

          Edited 9/5/2006 3:37 pm ET by xxPaulCPxx

          1. davidmeiland | Sep 06, 2006 05:53am | #23

            I smell a new invention coming up, another carpenter gone industrial millionaire. You can outsource the manufacturing to Asia, and license the marketing to Dupont or Grace (can you say 'bidding war?'). I'd figure a 1-1/2" x 250' roll for about $80 would sell fine. Now all you need is a name.

          2. User avater
            ProDek | Sep 06, 2006 06:56am | #24

            I'll go with Piffin on letting the ACQ pressure treated joists do what they are intended to do. We don't need another step in the process of building a deck by covering something that was intended to be used in all types of weather.

            Vycor was designed to save the metal fasteners, flashing, and post bases from the corrosiveness of the ACQ. It is the only way Simpson will warrant their hangers and brackets.

            I use all stainless hardware for the decks we build. The hangers alone are $5.33 each.

            The only reason to cover Joists is because the individual was too cheap to buy treated joists to begin with or the deck was built before treated wood, in which case the framing should all be replaced because the non-treated joists will not hold a nail or screw because they are too soft due to years of moisture. "Rather be a hammer than a nail"

            Bob

          3. User avater
            xxPaulCPxx | Sep 07, 2006 06:02am | #28

            "CRX Strap", of course.  Thanks for the vote of confidence!

            Of course it would go in with nails Bill - I'd have to make people who use nails with it submit an engineering report before they could put a nail through it.

            Just cause I'm a weenie :)Rebuilding my home in Cypress, CA

            Also a CRX fanatic!

      2. BillBrennen | Sep 06, 2006 07:53am | #25

        I like it! Has to be installed with screws, though ;-)

        1. SBerruezo | Sep 06, 2006 08:25am | #26

          Our weather stays pretty nice for the most part--we don't have to worry about the PNW weather of semi-constant fog and rain.  We used PT for all the framing, but I always kind of question the stuff.  It's seems great until you cut it or penetrate it, but then you expose the white untreated wood, and compromise the board.  So we use Vycor or  Sonneborn NP1(smoothed out) to seal the tops of all the framing, to prevent water from traveling down the screws into the white wood.  I don't know how much of a problem it is to have white wood exposed on PT, but we all felt a bit better using the Vycor or Sonneborn.

  4. peedee | Sep 04, 2006 05:09am | #9

    I've thought alot about this subject, too, and have recently come across a ~2" foil sided bituthane, alternatively (if the foil/ pt issue concerns you) you could go with the 6" paper faced bituthane and cut, though obviously if there's a lot of linear feet cutting would be tedious. Still, imo, it's the best long-term idea I've seen so far... aside from some type of standoff (but I haven't seen anything made for this application yet).



    Edited 9/3/2006 10:12 pm ET by peedee

  5. Notchman | Sep 04, 2006 05:20pm | #14

    Your joists should be pressure treated....I'm south of you, on the Oregon coast.

    Just pulled up a 20 year old deck....joists were fine.

  6. RyanBrant | Sep 05, 2006 10:20am | #18

     

    We've taken to painting all the upper surfaces of the PT joists and girders with liquid epoxy, and when the boss isn't feeling rushed, I can get him to paint all four sides.  It impregnates/encases the wood fibers making them waterproof.  On our last deck we used almost three gallons total I think for 400 sq. ft. of decking.  Expensive though, a two gallon kit (of parts A and B, one gallon each) costs around $140.

    1. johnharkins | Sep 05, 2006 08:53pm | #20

      I'm liking that approach but worrying about "encasing" the whole boardwhen I'm using PT wood I want green stuff & that usually means considerably wet lumber that should not be encasedthe majority of dry material in a yard will be so torqued & twisted it is not worth loadingbut that top edge is usually dry enough for epoxy / I'll use that
      thanks John

  7. Roxy2Madison | Aug 21, 2011 05:19pm | #30

    Protecting joists from rot

    There's a product I found that is cheap and seems to work excellently. It is called Deck Flash Barrier and is made by CoFair Products. Look them up online and it gives you an option of retailers in your area.

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