Which ply to use external

[crappy]

Folks,

I want to build a tennis wall in the garden. I am going to use 3 100x100 posts for the supports and then 3 18mm ply screwed to them.

Is all ply the same if I paint it? Anything better than other for perminent outdoor use?

C

 

[Deleted member 174758]

You need a hardwood ply, as opposed to a softwood one, and it needs to be an exterior grade board (what they used to refer to as WBP ply = "water and boil proof"). You will need to pay particular attention to sealing all the edges thoroughly with an oil-based paint or lacquer/varnish. I'd probably add an overhanging pressure-treated softwood lipping to the top and end edges which will further protect the edges from water ingress and damage (see attached illustration). Overall finish should ideally be with an oil-based paint as opposed to a water-based paint - simply because it lasts longer. Some people will doubtless recommend marine grade plywood - all I'll say is good luck trying to find it at anywhere near a reasonable price.

 

[crappy]

thanks.

Yes, I was going to add a bead to the edges and top. The top I was thinking of giving a decent overhand of around 100-150mm. It will not protect it all but will stop a fair amount I think.
Yes, marine grade is silly money at the moment - not that anything is sensible.

I will look at the hardwood option. Everything I have bought from Wickes before seems rubbish and is either not bonded correctly or splits soon after I use it.

Noted on the oil-based paints. Thanks.

 

[freddiemercurystwin]

Overheard a guy from B&Q the other day saying all of their plywood is hardwood but who knows ....

 

[Deleted member 174758]

Sorry, bit of a c*ck upwith the drawinghs - missed them off . Here they are:

Above: Main structure from front showingcaping and tapered end cover
Below: From rear showing 2 x 2 treated softwood perimeter framing (to reduce bowing and stiffen the structure)

Above: Showing the sort of capping needed. The drip groove on the underside at the front is cut by making a 3mm deep saw cut with a circular saw something like 10mm in from the front edge so any water running off the top runs under, hits the groove and drops off. The capping ideally needs to cover the tops of the posts as well so as to protect them from water soaking into the end grain and starting rot. I'd also consider running a bead of silicone along the edges between the cappings and plywood as well as between the plywood sheets to reduce water ingress - it won't last forever, but it will slow down decay

 

[freddiemercurystwin]

I would think an overhang at the front would have your balls pinging off in completely random directions should you hit them (Oo'er Missus).

 

[crappy]

it's a daily challange I struggle with at the moment....


oh, sorry, wrong group!

 

[Deleted member 174758]

I would think an overhang at the front would have your balls pinging off in completely random directions should you hit them (Oo'er Missus).

The problem is that if you don't protect the edge thoroughly it will start to delaminate and potentially rot in a matter of months

 

[freddiemercurystwin]

Well for sure but does he want wonky balls?

 

[scbk]

I don't know anything about tennis, but can you not make it out of sawn boards ie 150x22 or whatever. They will last a long time.

Ply can be a gamble, I've seen what was apparently marine ply, painted on all sides with oil based gloss, and falling apart after a couple of years.

And then I've got some shuttering ply that was the cheapest of the cheap, and it seems to be lasting ok.

 

[SFK]

Can you use hardiebacker? (Concrete boards)?

 

[cdbe]

3 100x100 posts for the supports

It will probably blow over long before it rots.

 

[Deleted member 174758]

Can you use hardiebacker? (Concrete boards)?

They are certainly very weatherproof, but they are also very heavy (8 x 4ft approx. 12mm Versapanel is about 45kg), quite brittle and so I think they would require a substantial timber frame behind them.

I'm starting to wonder if a lightweight signage plastic panel such as Foamalux on a frame would be any better. Certainly gets round the rot issue

 

[SFK]

lightweight signage plastic panel

If going down that route I would use Aluminium Composite Sheets.
Super strong, and v light. But do get dints in them relatively easily.

https://www.ebay.co.uk/sch/i.html?_...1313&_nkw=Aluminium+Composite+Sheets&_sacat=0

 

[freddiemercurystwin]

But if you start looking at aluminum composites for example each board will be £££s, you could look at things like Trespa or similar if that's the budget ....