Replies

1. 
   rez | May 03, 2009 07:05pm | #1

   Dear Sirs,  I have just finished siding a craftsman bungalow (self built for my wife and I), and am about to start painting.  The project has been delayed and went thru this last winter without painting.  Of issue is the underside of the exposed eaves which are constructed of 3/4 inch plywood on top of 2x8 rafters with asphalt shingles over.  I asked for the best AC ply wood available and not knowing any better used the pine plywood supplied by my local lumberyard.  Over the winter the high humidity in WA state allowed mold growth on the exposed underside of the pine ply and to a much lesser degree on the underside of some fir AC I used.  Per their recomendations I used bleach to remove this from most but not all of the plywood.  Due to the delay in painting over the entire ply underside there are now fine checks/ hairline cracks in the face veneers.  What is the best way to paint seal this as I do not want the pine ply to mold thru the paint checked areas either because the paint doesn't properly seal the checks up or because of new checks opening up in the future.   Many differing options have been presented from just wash it with a mold inhibitor then rinse and paint it with oil based primers, to using a shellac wood sealer, to applying  ForSite mold inhibitor silver containing clear coat, to using only latex primers that have elastic qualities.  One mentioned was Zinsser Peel Stop with Sherwin Williams exterior Duration paint as a top coat.  One fellow even recomended a rubberized decking paint, another sealing the entire surface/ cracks with caulk first (using a squeege) then painting.   Any ideas?.

    

1. 
   Dam_inspector | May 03, 2009 09:31pm | #2

   I'm going to go with the idea of Zinsser Peel Stop with Sherwin Williams exterior Duration paint. Sand lightly prior to painting. Plywood is a poor paint base though. You may want to overlay it with some MDO plywood or other substrate eventually.

1. 
   rez | May 04, 2009 12:16am | #4

   See above posts. 

1. 
   stevent1 | May 04, 2009 01:51am | #5

   Welcome to BT,

   Remove the ply and replace with t&g primed 1x. Ply will not last unless it is marine grade, backprimedand edgeprimed.

    

   Chuck Slive, work, build, ...better with wood

1. 
   Sphere | May 04, 2009 02:34am | #6

   You realize that means stripping the shingles.Spheramid Enterprises Architectural Woodworks

   Repairs, Remodeling, Restorations

   "If Brains was lard, you couldn't grease much of a pan"Jed Clampitt

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2. 
   stevent1 | May 04, 2009 04:07am | #7

   D,

   Dear Sirs,  I have just finished siding a craftsman bungalow (self built for my wife and I),

   Of course I realize it means removing 2 or 3 courses of shingles. This will also give the OP a chance to prime and paint the tops of the rafter tails. Over the years I have been able to pay cash for additional work trucks from this type repair.

   When I built my small addition I preprimed the tails and 1x4 centermatched  sel&btr SYP.

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   The ends of the tails were notched 5/16" x 22 1/2" for the 7 rows of T&G to get above the top plates.

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   This allows the decking to align with the upsidedown flooring.

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   A lot of research planning but most of all knowhow is a big part of building/replicating a period home (As you well know).

   Chuck S

    

    live, work, build, ...better with wood

3. 
   Sphere | May 04, 2009 04:10am | #8

   Just checking buddy, I know ya know your stuff, just thought maybe ya missed that it was the decking, and not a soffit.

   My bad.Spheramid Enterprises Architectural Woodworks

   Repairs, Remodeling, Restorations

   "If Brains was lard, you couldn't grease much of a pan"Jed Clampitt

   View Image

4. 
   stevent1 | May 04, 2009 04:15am | #9

   D,

   No problemo (Tres de Mallo). I wonder what other issues are involved in that house?

   Chuck Slive, work, build, ...better with wood

5. 
   trekka | May 04, 2009 12:12pm | #10

   Dear Sir, Thanks for the input.  I have never seen that done before but it looks like a good idea.   I did not add that I questioned the sales staff repeatedly on the suitability of the plywood before buying it and after it was delivered before using it. 

   Being from down south I have never seen plywood grow mold nor experienced two weeks of constant rain in august.   If there is a source of information on building techniques for wet climates I would appreciate knowing it as I have never seen your method in print either.

   Other nearby houses are using t111 (no groove) which is painted before being nailed down and it is holding up fine.   Obviously one could overlay the eave underside with a 1/4 inch thick hardi panel.  I don't know if there would be any issues with condensation betweeen the ply and hardi causing mold or rot  however.  

   The rest of my house is all fir framing lumber, cedar trim, all galvnized nails, 1/2 inch 5 ply cdx sheathing, 3/4 inch fir ply subfloor and some osb advantek subfloor which despite it's 300 day warranty suffered edge swelling creating 3/16 inch ridges.  Given what I have seen it seems that pressure treated ply might be the way to go and I would appreciate your input as to what products you use for sheathing, flooring, roofs, and siding.

   Anyway fortunately I am young enough that I have the time to fix it and do the next one correctly. 

6. 
   stevent1 | May 04, 2009 06:48pm | #13

   I am not familiar with what materials are best for your part of the country. Stop by some home sites(not tract homes) and see what they are using.1/4" hardie overlay may create a mold sandwich.I have yet to see a problem in using Advantech.Good luck with your house.Chuck Slive, work, build, ...better with wood

7. 
   florida | May 04, 2009 02:24pm | #11

   "Ply will not last unless it is marine grade, backprimedand edgeprimed."
   Say what? Does that mean I have to go back and rebuild all the sheds and houses I've built in the past 35 years with that very detail? Built with unprimed 3/4" CDX. They've held up just fine down here in humid, wet south Florida.

8. 
   KenHill3 | May 04, 2009 05:58pm | #12

   I have used some pine plywood here in Washington State that was real cr@p- bowed, checked, cracked, voids, you name it. Because of this and other bad experiences with ply I am very careful now when buying ply for applications where things matter- like open soffits!

9. 
   stevent1 | May 04, 2009 06:57pm | #15

   I guess that was a stong statement on my part. I am not saying ply cannot be used successfully but I have done a lot of repairs when it has failed.The OP has mold issues and I was offering an alternative method.Chuck Slive, work, build, ...better with wood

10. 
    florida | May 04, 2009 07:24pm | #16

    I'm messing with you. I've actually tried to talk some customers out of open plywood but failed. We used to houses with T1-11 face down on the roof to mimic sheathing boards. I know some designs call for open soffits but they sure are hard to keep clean.

2. 
   Biff_Loman | May 03, 2009 09:40pm | #3

   Thanks. I can't even start to read text with no paragraph breaks.

2. 
   wallyo | May 04, 2009 06:50pm | #14

   trekka

   I would sand as much of it as possible and use a heavy body primer like the zinsser or KILZ¯ Premium. I would give it two coats of primer making sure you brush it into all the grooves and cracks throughly. Or roll it and back brush it. Then top coat with a good quality paint.

   If you can wait for a week of good dry weather before starting all the better. When it comes time to re-roof if you are still living there then you replace the ply. The choice of oil, water or alcohol based is up to you I think they are all almost equal now.

   Wallyo

1. 
   trekka | May 05, 2009 10:28am | #17

   Has anyone used the product FORSITE (a silver containing anti mold paint), as an exterior first coat with latex primers and topcoats over it?  Several of the stores carry it here to spray out the stud cavities prior to insulation.  There is a blue and a clear that supposedly can be used outside but the directions are vague on topcoating.

1. 
   wallyo | May 05, 2009 04:58pm | #19

   Heard of it never used it call the manufacture, I think it is not meant to be top coated, but that does not mean it can't be top coated.Trekka can you post some pictures, I think once sealed that will control any further checking.But pictures would help people understand how severe the problem is.Wallyo

1. 
   trekka | May 10, 2009 01:35pm | #20

   Thanks for the comments.  I spoke to the ForeSite people who confirmed that their silver based anti mold coating is a topcoat and not a primer. 

   After being wiped down with bleach and then mold avenger and rinsed, there isn't anything to photograph except some checking in the face veneer of the pine plywood. 

   The real story will be how it holds up long term after three coats of paint.   I may end up doing the Hardi overlay between the rafters if I am not happy a year  from now.

3. 
   alwaysoverbudget | May 05, 2009 03:46pm | #18

   i know this isn't the design of a bungalow,but i would say skrew it, and hang a sofit out of hardi and go on.

   i think if it's cracked up now ,it's never going to uncrack,it's just going to get worse.

   my next option would be to go in and overlay it with hardi between each rafter.

   YOU ONLY NEED TWO TOOLS IN LIFE - WD-40 AND DUCT TAPE. IF IT DOESN'T
   MOVE AND SHOULD, USE THE WD-40. IF IT SHOULDN'T MOVE AND DOES, USE THE
   DUCT TAPE.