Advice required

[jethro110]

Hi all

i have slabs of 50mm x 500mm natural edged Ash which has been drying for a couple of years and i would like to make this into an outside patio table.

If i cut two of the edges to make a center join, should i use biscuit joints?
should i position the join the lengths so the grains run the same way or one up and one down?
do i need to put a finish on the finished product?

thanks

 

[RobinBHM]

If you are going to leave the table out to get rained on, I would say dont use ash -it is not durable at all

 

[MattRoberts]

Hi. If you have a biscuit joiner, then sure, use it. It helps add strength as well as helping with alignment.

Not sure what you mean about the grain, but you should definitely join long grain to long grain. If you're talking about alternating grain direction, that only really matters of your joining multiple slats of wood, to help avoid cupping. It's less applicable for two large slabs.

And yes you need an exterior finish, as well as using waterproof glue

 

[Dan j]

Hi.
Ash has very little natural durability. Clear wood preservative before a final finish is probably a good idea, especially on any end grain that's exposed.
If the legs are ash it might be worth putting a sacrificial piece on the end of the legs to stop damp seeping up into the end grain and then replacing it as it rots. You can see the idea here.

 

[Phil Pascoe]

I did the bottoms of the legs of a garden table many moons ago with flashband, purely because I happened to have some at the time and it lasted 15 years last I looked (moved house). And yes, unfortunately - ash rots while you watch it.

 

[woodpig]

Just thinking out loud here but if you really want to use the Ash outdoors perhaps you could finish it with 2 pack yacht varnish?

 

[Random Orbital Bob]

Morgan frames seem to last "outside" for a fair time!! As did all traditional coach work I appreciate Ash isn't one of the natural choices for outside work like the oily woods (teak etc) but if properly treated I see no reason why it cant last.

Some of the above ideas about sacrificial feet and decent quality treatments would lengthen it's life considerably.

 

[ED65]

If i cut two of the edges to make a center join, should i use biscuit joints?

They'll help with alignment, I wouldn't have thought any help was needed in that regard with boards this thick and just the one joint.

should i position the join the lengths so the grains run the same way or one up and one down?

It depends on how the top is attached whether it's better to alternate or not from what I've read. If they're oriented the same way you know the tendency is for the table to bow in a single direction right? This is supposed to be easier for the fasteners to hold in check than one board up and one board down.

 

[ED65]

If you have a biscuit joiner, then sure, use it. It helps add strength as well as helping with alignment.

There'd be no strength increase in this situation, at least none that's needed. Biscuits add a lot of strength to mitres, but long-grain butt joints are already as strong as the wood.

 

[MattRoberts]

If you have a biscuit joiner, then sure, use it. It helps add strength as well as helping with alignment.

There'd be no strength increase in this situation, at least none that's needed. Biscuits add a lot of strength to mitres, but long-grain butt joints are already as strong as the wood.

Having what are effectively tenons join the wood would be a strength increase, but I agree it would be pretty minor and not strictly necessary

 

[ED65]

Having what are effectively tenons join the wood would be a strength increase

They're not exactly like tenons which is probably the salient thing in practice. Odd as it seems for a joint like this the more biscuits you add the weaker the joint becomes. Each one is a discontinuity in the long-grain glue line and each of them provides a site from which cracks (failure of the glue line) can propagate.

Now realistically in either case glue-ups are almost always going to be strong enough, but if the panel is to be under significant load the difference is worth knowing.

 

[Fitzroy]

TLDR: Use more coats of finish on the table top than you think you need, the water sits and buggers it! Stand the legs in Barrettine overnight before drying and finishing.

I made an outside table in oak last year and my observation is that the top has taken a real beating from the elements. The top design is probably flawed in that it is a continuous surface so water sits (and we get a lot of water in Aberdeen), I should have left some gaps between the timbers. The wood work under the top has fared very well with all the mortice and tenons etc still fully functional and the legs pretty much unchanged after a year outdoors. The whole thing was finished with a coat of Barrettine wood preserver and 2 coats of Osmo UV protection. I took heed of some advice and stood the legs in the Barrettine overnight, I don't know the leg timber but I don't think it's durable, and they are looking great. I should however have put at least 4 or more coats on the table top!

 

[jethro110]

thank you all with your help

 

[Paul200]

Well I learned loads from this 8) (hammer)

Thanks guys!