How to make untreated ply more weather resistant?

[Greenman84]

Hello. I have some untreated plywood I've been using for building a chicken coop. I've painted it with 3 layers of exterior paint. I've just been wondering - is there anything I can add to make it more weather resistant?

I've seen mixed info about things like clear coat water based polyurethane. Is it definitely not a good idea to apply something like this? Or will the paint be enough? the housing will be off the ground and the roof will overhang  a bit - will this be okay in the rain? 

I was thinking of sealing the edges with some of that selly's storm stuff - is that a good idea?

Any help much appreciated.

Thanks.

[EricL]

Hello @Greenman84 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your chicken coup. 

I believe for the moment the 3 coats of paint will be enough to protect the untreated plywood. It certainly would not hurt to put some Selleys storm on the edges and joints. Would it be possible for you to post a few photos of the chicken coup? Perhaps we can add a few more ideas to keep it dry and protected. 

Let me call on our experienced members @Dave-1, @Nailbag, @JoeAzza and @woodalwaysworks for their recommendations.

If you need further assistance, please let us know.

Eric

[AlanM52]

Hi @Greenman84,

You have opened a can of worms mate.

I have been doing the backyard chicken thing for thirty years and also helped many people build their coops and chook runs.

I have also been to places to help people repair what they have built and often get comments like 'Yeah... we did all the right things and the plywood was good for a while but now the weather is getting to it'.

The summary is even with marine plywood properly sealed and painted there will be ongoing maintenance - ongoing  $$$.

You have already done three coats so leave it at that and follow up with this.

Line the outside with polycarb roofing sheets and flash the top edge - done.

I also strongly recommend you line the inside with this - Why is that?

That is a cell structure and the ends must be sealed to keep out mites.

Unfortunately you have chosen the worst material to build a chicken coop, timber is a haven for mites.

Having said that for coop furniture like nesting boxes laminated chipboard is OK but the edges must be sealed with iron-on tape.

Hope I have been helpful...

Cheers

[Nailbag]

Hi @Greenman84 

After 3 very good coats of exterior paints to all sides you should be right. But you will need to keep the maintenance up on fresh coats to prevent it delaminating especially on the edges. A good silicon like @EricL suggests on all joins is ideal or a Sika product. This would need to be used to seal over any holes for bolts or screws that breaks the pain seal. 

Along the lines of @AlanM52 concerns consider one day a more suitable roofing product to layover the existing like polycarbonate or colourbond. 

look forward to a few photos

Nailbag

[woodalwaysworks]

I used structural plywood on a section of our kids playground and used a bitumen/tar sealant.

Let it dry for several days

Exterior Undercoat, Followed by a Strong, paint colour, exterior paint. I used dark green. Paint stuck to the sealant and the ply is still good 4years on. Gets a lot of abuse from the kids to.

 

[Dave-1]

Good morning @Greenman84 

Welocme to the community And as @AlanM52 has said you have opened a can of worms!  

I like the idea of having a waterproof edge to the top side of your plywood sheets, something to stop the water getting in easier. Maybe an angled piece of flashing? Otherwise 3 coats for now and when it gets to a point then replace with something else. The mites are the thing I have also read about (I dont have chooks but do have a 2/3rd completed chookpen) that would be worth keeping an eye out as they love to hang out in those cracks that develop as plywood perishes.

Dave

[JacobZ]

Hi @woodalwaysworks,

It looks really good after 4 years.

Did you have any issues with the undercoat adhering to the bitumen sealant?

Do you remember which specific undercoat you used?

It clearly worked, I just can't say I've seen it done before, so I am intrigued. 

Thank you for sharing your experience. It looks like it could be a good option for others in the future.

Jacob

[woodalwaysworks]

I have a fencing business and when installing posts bitumen always finishes 150mm-200mm above ground. Painters I sub contract out never seem to have a problem priming over it. Only frustration for them is they have to get the brush out and apply several coats as the sprayer isn’t adequate.

Can’t remember which brand I used sorry 

[JoeAzza]

Hi @Greenman84 , Just to add to the discussion,  a few years ago I made a plywood letterbox, I used marine ply, I undercoated and painted it with acrylic paint, it still needs to be maintained on a regular basis,  showing signs of cracks, however no delamination of the plywood, not how long your plywood will last, maybe if it was undercover, it might last a lot longer.