biscuits outside

[Jerry Spitz]

Can biscuits be used on exterior projects, tables, chairs etc. ?

[Phil Thien]

Yes, as long as you use suitable glue.

[Wade Lippman]

Festool considers it essential to use sipo dominoes outdoors rather than regular ones.
I don't know if they are right, but I presume the same applies to biscuits.
Of course, if you are just using them for alignment, a little rot might not matter.

[Phil Thien]

Wade brings up a good point. Of course, you can find (Google) lots of exterior projects made with regular Dominos, and you can certainly find tons of exterior projects that call for just regular biscuits, like this:

http://www.familyhandyman.com/DIY-Projects/Outdoor-Projects/Patio/Patio-Furniture/how-to-build-a-garden-bench

And of course, exterior doors and windows have been made for decades with plain dowels (albeit large ones).

I imagine that if moisture has penetrated a joint to the point where it hitting the biscuit or Domino or dowel or whatever, you have bigger problems that whether or not your tenon is water resistant or water proof.

[Jerry Miner]

I wouldn't do it. I've had the task of repairing many pieces of outdoor furniture that were constructed with teak lumber and maple or birch dowels. The teak held up great, but all the joints failed when the dowels rotted.

An outdoor table or chair is a different thing from a window or door: much more exposed, outdoor furniture gets ALL the weather, not just whatever gets past the roof overhang, like a window.

Maybe plastic biscuits and epoxy? Make your own biscuits from a resistant specie? IMHO, if you use standard beech biscuits, you are asking for joint failure down the road.