Thickness of Marine Ply or other options for outdoor training wall (domestic)

Hello,

I live in Australia and wanting to build an outdoor training wall off the side of my house (iso has made me realise I need this in my life haha!). We do get rain throughout the year and it won't be under cover.
 
My question is, what thickness of marine ply should I get? There is a significant price difference from all-purpose ply to marine and then also between thicknesses. I obviously want to spend the least I can on the ply, but won't skim on quality, so that the wall actually serves its purpose haha. If it matters, I am only 5'5" and ~58kg.  

Has anyone here built an outdoor wall and not used marine ply?

Thank you! 

Brighley Dangerfield wrote: Hello,

I live in Australia and wanting to build an outdoor training wall off the side of my house (iso has made me realise I need this in my life haha!). We do get rain throughout the year and it won't be under cover.
 
My question is, what thickness of marine ply should I get? There is a significant price difference from all-purpose ply to marine and then also between thicknesses. I obviously want to spend the least I can on the ply, but won't skim on quality, so that the wall actually serves its purpose haha. If it matters, I am only 5'5" and ~58kg.  

Has anyone here built an outdoor wall and not used marine ply?

Thank you!

I did.  I used 3/4 or 17mm cabinet grade ply. $35 usd a sheet and i stained the $hit out of it with water seal.  You have to put a roof or tarp on the back though because the wood will swell through tnut holes and probably won't last 6 months. You can also get corrugated metal panels and just put them on back. Those are about $33 usd for a 2ft x 12ft piece. 

Yep, a roof on the back is fairly key as well, and keeping the Tnuts lubricated or buying all stainless hardware. Pressure treated 3/4" plywood is really strong if you can get it. I made an outdoor wall out of pressure treated 5/4" decking boards instead of plywood and it worked great.

Thanks for the reply guys. Ended up purchasing 18mm Marine ply super cheap from a guy who had some left over. The back will already be covered by the roof, as there is an overhang (of the roof) of about 20cm.
Will post a picture when it’s up (pending the huge shortage of holds we have in Australia at the moment)

Out of curiosity, what is the benefit of marine grade ply in the context?

Evan V wrote:

I did.  I used 3/4 or 17mm cabinet grade ply. $35 usd a sheet and i stained the $hit out of it with water seal.  You have to put a roof or tarp on the back though because the wood will swell through tnut holes and probably won't last 6 months. You can also get corrugated metal panels and just put them on back. Those are about $33 usd for a 2ft x 12ft piece. 

How did the water seal work out for you?

We threw together an outdoor wall and framed it with pressure treated 2x4 and 4x4 so I know that's solid.  We repurposed the panels from a friends indoor wall and they are unpainted except for a quick coat on the front of the plywood.  Totally expect the panels on there now to die a quick death and they have already started swelling badly in a few weeks.

The plan was to used 4'x4' sections of 3/4 cabinet ply and will band the edges to seal them well.  I have been debating on either oil primer and then exterior latex paint and sand for grit (after drilling to hopefully seal the holes a bit) or coating the hell out of the panels in thompsons waterseal or something similar.  I'd actually prefer to water seal instead of paint because it looks nicer, will get in all the nut holes better and is a one step process but wasn't sure it would hold up and also though it may be a bit slippery.

Right now the back is uncovered and it's overhanging so the back is taking a beating.  Once we have long term panels up I was going to cover the back in tyvek house wrap so it stay dry but can breath a bit.

Also on hardware the black oxide bolts look like hell after a few weeks but the zinc nuts look good.  I'm thinking of ecoguard bolts from fastenal and zinc t-nuts.  Ecoguard is supposed to be saltwater rated and waaayyy cheaper than stainless

Live Perched wrote: Out of curiosity, what is the benefit of marine grade ply in the context?

Marine-grade just already has the water sealant in it when glued together. The glue used is waterproof and eliminates the need for adding varnish or sealants prior to installation. By the name, it's used in the boat making industry mostly as the structural support for fiberglass hulled boats. 

V P wrote:

How did the water seal work out for you?

We threw together an outdoor wall and framed it with pressure treated 2x4 and 4x4 so I know that's solid.  We repurposed the panels from a friends indoor wall and they are unpainted except for a quick coat on the front of the plywood.  Totally expect the panels on there now to die a quick death and they have already started swelling badly in a few weeks.

The plan was to used 4'x4' sections of 3/4 cabinet ply and will band the edges to seal them well.  I have been debating on either oil primer and then exterior latex paint and sand for grit (after drilling to hopefully seal the holes a bit) or coating the hell out of the panels in thompsons waterseal or something similar.  I'd actually prefer to water seal instead of paint because it looks nicer, will get in all the nut holes better and is a one step process but wasn't sure it would hold up and also though it may be a bit slippery.

Right now the back is uncovered and it's overhanging so the back is taking a beating.  Once we have long term panels up I was going to cover the back in tyvek house wrap so it stay dry but can breath a bit.

Also on hardware the black oxide bolts look like hell after a few weeks but the zinc nuts look good.  I'm thinking of ecoguard bolts from fastenal and zinc t-nuts.  Ecoguard is supposed to be saltwater rated and waaayyy cheaper than stainless

I’m not a big fan of treated ply. It comes swollen and when it dries out it shrinks and you have to be careful on a wall that the screws stay tight and it is ugly. 

I opted for cabinet grade because I was gonna treat it myself and I am gonna put a roof on it as soon as I get the rest of my tnuts. I’m tapping mine this week to be safe.

I would not use any type of paint. It will definitely flake off within a short period.  If you treat yourself w a water seal make sure you drill holes first so when you are rolling the stain on it goes in the holes a little.

I ordered a few hundred stainless steel bolts on amazon from escape climbing I think. They were like .25 each I believe. 

Ryan Brown wrote:

Marine-grade just already has the water sealant in it when glued together. The glue used is waterproof and eliminates the need for adding varnish or sealants prior to installation. By the name, it's used in the boat making industry mostly as the structural support for fiberglass hulled boats. 

Cool, thanks.  Makes sense. When I’ve bought ply at the marine shop for a boat, I never had the impression it is water proof.  But I sniffed a lot of varnish over the year.  

M Mobes wrote: I made an outdoor wall out of pressure treated 5/4" decking boards instead of plywood and it worked great.

I'm liking this idea more and more.  I priced it out and not much more than good plywood but already treated and is solid wood.  A win/win in my book.  One line of t nuts down the center of each board and you can easily do 6x6 spacing.

Slightly annoying to screw in 22+ boards but seems like it would be way more solid than plywood and more modular to replace pieces of wood as needed.  I planned on taking the wall panels off for winter to save the abuse and to keep snow from building between the wall and my house.  It will definitely suck taking them all on and off but easier storage I guess...

V P wrote:

I'm liking this idea more and more.  I priced it out and not much more than good plywood but already treated and is solid wood.  A win/win in my book.  One line of t nuts down the center of each board and you can easily do 6x6 spacing.

Slightly annoying to screw in 22+ boards but seems like it would be way more solid than plywood and more modular to replace pieces of wood as needed.  I planned on taking the wall panels off for winter to save the abuse and to keep snow from building between the wall and my house.  It will definitely suck taking them all on and off but easier storage I guess...

I’ve seen a few walls w 5/4. It looks more organic than ply as well.

Marine plywood uses an adhesive that is not affected by water. However, the wood plies themselves remain susceptible to water and the face plies and exposed edges must be sealed for exterior use. Marine plywood uses high quality (knot and void free) plies and veneers, which give it better strength and resistance to delamination than other types of plywood. Specialty plywoods such as Baltic birch are similarly void-free, but are not made with glues that are suitable for outdoor exposure.

Exterior plywood (usually designated CD-X in the US) also uses a water-proof adhesive, but may contain internal knots and voids. These make exterior plywood more prone to delamination than marine plywood, especially if a cut edge is through a void or knot. A t-nut through a knot or void could pull out (effectively, the plywood would act as if it were thinner than its nominal thickness) or tightening the bolt could crush the plywood.

With either marine or exterior plywood, the t-nut holes are going to be a route for moisture intrusion to the interior.

Properly treated, marine plywood will withstand immersion--I know an industrial plant that built chemical storage tanks using marine plywood and many coats of polyurethane.

Evan V wrote:

I’ve seen a few walls w 5/4. It looks more organic than ply as well.

The rounded edges paired with wide gaps makes a decent wall with no holds on it.

M Mobes wrote: Yep, a roof on the back is fairly key as well, and keeping the Tnuts lubricated or buying all stainless hardware. Pressure treated 3/4" plywood is really strong if you can get it. I made an outdoor wall out of pressure treated 5/4" decking boards instead of plywood and it worked great.

Do you have any photos of your wall?  I am thinking about the same, and wasn't sure about how many Tnuts to get versus using plywood.

Hans Climber wrote:

Do you have any photos of your wall?  I am thinking about the same, and wasn't sure about how many Tnuts to get versus using plywood.

About the same amount of Tnuts, you always want plenty. You do end up staying a couple inches from the edges when drilling, or at least I did. The nice thing about the decking is that its pre sanded, edges rounded over and the cuts of lumber are fairly quality. 

M Mobes wrote:

About the same amount of Tnuts, you always want plenty. You do end up staying a couple inches from the edges when drilling, or at least I did.  

Awesome thanks.  I would still love to see some photos if you get a chance.  

Hey everyone,
ended up building the wall and here it is!
There’s a time lapse up on my Instagram if you were interested in seeing that too: @being.faabulous 

I’ve also added a roof too. Climbing holds and crash mats are on the way

That looks  nice but maybe it should be over a pool. Padding is key.