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using sheathing as siding?

modernreclaimer's picture

using sheathing as siding? (post #215565)

Hey guys, I'm building a small house with mostly reclaimed materials/new materials that friends and relatives had leftover. I was given a large amount of plywood that used to be used for crates in a tomato processing plant. The panels are 41" by 39" and 1 1/8 inches thick. My original plan was to use the plywood as sheathing (structurally it's overkill to be honest) and clad it with hardie plank that a family member had extra from building a house. 

However it looks like there is only enough hardie plank to do about half. I can't afford to buy any more hardie plank and I've already put up all of my sheathing so I have to make a decision about siding. Since I don't like the appearance of cheap siding and the look of the patched together reclaimed plywood is actually quite beautiful I've been trying to work out a way to seal it and leave it as the exterior siding.

Problems with this as I see it: Sealing the seams. I would have no tyvek on the plywood only walls since I didn't put it down before hand. Installing windows on the outside of what is now the siding. Weatherizing the plywood itself.

Is there a product I can use to coat the walls and seams, perhaps marine varnish or epoxy over caulking in the seams? Or is this just too farfetched? Thanks for your input.

FYI, I also have three foot overhangs and live in California where it only rains a few months of the year, no snow.

Hi there,  If you could post (post #215565, reply #1 of 13)

Hi there,  If you could post a few pictures of what your plywood siding looks like installed we can probably offer suggestions on how to detail the seams etc.  Without seeing it however, I would recommend flashing the horizontal seams with "z" flashing or 1 1/8" window cap flashing which is a common off the shelf item.  The vertical seams can be covered with battens.  As for coating the exterior...  a good quality oil primer and 2 latex topcoats would be my choice.  

Thanks for your response! It (post #215565, reply #2 of 13)

Thanks for your response! It won't let me upload pictures for some reason, I'll try again later. I don't think batons are a possibility because it really is like a patchwork wall. Some pieces are smaller than a square foot and theyre all staggered and pieces together to fit. Very sturdy but not conducive to putting on battens.

I think I'm looking for something that's more glue like and can fill in the cracks and weatherize the plywood but I'm not sure how well that would work. Hopefully later tonight I can resolve this picture issue.

 Hi again,        It (post #215565, reply #3 of 13)

 Hi again, 

      It seems like you really just need a good exterior sealant. 3M makes marine grade sealants like 5200 that are permanent.  They are designed/rated for below the "waterline" on boats so can definitely handle rain and weather on sidewalls.  The only issue with using this product is it's high cost will negate the savings you were looking for in skipping siding in the first place.  I think 5200 is around $30/tube.  I might consider a good paintable caulk like Tower or Phenoseal and just plan on keeping tabs on it and maintaining it's integrity.  Given your locale, that may be all you need.  My brother lives in Santa Monica and owned a old Ford Bronco with no top for about 5 years.  I asked him what he did with it when it rains and he laughed.  He said it has rained about 5 times that he can remember since he moved there in 1998.  

Haha that sounds about right (post #215565, reply #5 of 13)

Haha that sounds about right for Santa Monica, here in northern California we get a little more rain than Santa Monica, but on the north nonwind side it just isnt a huge issue.

I've added three pictures to my original post to give you a better idea.

I'm doing my research on the products you mentioned right now, I do have to admit though that while price is big a motivator here, the fact that the look has grown on me and that applying a seal seems easier than installing hardie plank are also factors...

Do you think the air tightness of the walls is an issue with something like this over traditional siding?

You don't say whether this (post #215565, reply #4 of 13)

You don't say whether this plywood has any sort of exterior rating.  I suspect it doesn't.  You should either coat it with a resin-like coating or with self-adhesive plastic membrane.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

I'm pretty certain the (post #215565, reply #6 of 13)

I'm pretty certain the plywood doesnt have an exterior rating, but i've got some pictures up now so you can see what i have. An adhesive mebrane is something i hadnt thought of, ill look into it more.

Two questions: would a resin like coating be viscous enough to stay in the cracks and effectively seal them? And would it cause an issue in terms of the breathability of the wall to be putting this sort of (Im assuming) vapor resistant barrior on the outside? 

Resin coating? Plastic (post #215565, reply #8 of 13)

Resin coating? Plastic membrane? 

Watch out for UV exposure and I dont think you'll find a membrane that doesn't make the place look like a self storage unit

Have you seen the pictures?  (post #215565, reply #9 of 13)

Have you seen the pictures?  A FEMA tarp would be an improvement.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Haha... dangit (post #215565, reply #10 of 13)

Haha... dangit

C'mon man (post #215565, reply #7 of 13)

least you could have done is put the tomato crate right side up........

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


think short term/long term (post #215565, reply #11 of 13)

If that were mine I think I'd caulk the seams with acrylic latex [cost effective] then paint it with whatever decent exterior paint I could

find cheap while I kept an eye out for some nice siding for the long haul. 


What everyone else said. I'd (post #215565, reply #12 of 13)

What everyone else said. I'd caulk the seams with a good elastomeric caulk, work it in with a putty knife and feather the edges as much as possible. A light wipe with a damp sponge will clean it up too. Then I'd prime with a good exterior latex primer and top coat with elastomeric paint.  That will see you through many years until you can afford more Hardi. You'll still need corner and window trim though.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Thanks for the detailed (post #215565, reply #13 of 13)

Thanks for the detailed advice