Andy Dingley wrote:
On 6 Mar, 11:58, wrote:

So you'd get slight gaps if the planks aren't T&G.

Tongue & groove is too thin and fragile for outdoor use, unless it's
so big that it will look clumsy. You're better with half lapped
rebates instead. It's also easy to cut rebates with DIY hand-tools,
but grooving is more troublesome.
Good point.

But I don't think t & G 19mm planks is inadequate for garden use in oak,
at the least.

And a table router will sort it out.