Outdoor furniture, how wide can the slats be?

[ol_london]

I am making a garden table and bench out of European oak, and having looked at various designs it seems the common theme is to have slats rather than joined pieces. Presumably this is for drainage of rainwater. But my question is how wide I can make each slat while keeping it effective? I don’t want to use lots of thin pieces, ideally I’d want to use some 170mm wide boards (25mm thick) that I already have without ripping them down. I prefer the look of wide boards.

Is 170mm going to be too wide for drainage to work and avoid the wood warping or can I get away with it? Thanks...

 

[Alpha-Dave]

As with all furniture it is part aesthetics and part practicality. I have a bench made from oak sleepers (new), that are 200x100 mm in cross section. Drainage is fine. You can chamfer the edges to encourage draining.

I suspect that a 7:1 ratio like you have will twist, bend and split over time as it dries, re-wets etc. It should still be structurally good enough though.

 

[MARK.B.]

Bit of a trade off-wider boards may look more pleasing but more chance of cupping, ripping your boards would yield two 80mm ish boards that would look fine and reduce(possibly) any future problems with movement.

 

[ol_london]

Thanks. So no definitive guidelines on width, sounds like the best thing is to rip them in half as a precaution. I’d rather not but better that than it splitting etc.

 

[Br5d]

I use flat sawn slabs up to 600mm wide with no problems (mainly white oak) the only caveat would be to seal the timber well.

 

[Adam W.]

Join them together, but don't screw them onto a stretcher. Make a housing for that and the top can sit on it and move with the weather.

It will move a lot, mind.

Mine cups and bows, depending on the season, but hasn't split and it's been outside for 5 years with no treatment on it. It's made from 2" by 9" flat sawn, sap free boards edge jointed with slip tenons.

 

[Jacob]

In general the smaller the cross sectional area of a piece of wood the more likely it is that it will dry out in between soakings and delay the onset of rot

 

[TominDales]

In general the smaller the cross sectional area of a piece of wood the more likely it is that it will dry out in between soakings and delay the onset of rot

Thats interesting. I'm making a posh swing seat out of oak and the design is one solid piece of wood 60cm by 20cm by 3.5cm. its in a separate post. I was planning to leave it out all summer. It probably only has to last another 5 or so years as the youngest will be old by then, although we have big kids that like to loll on it. Would a slat design be better? I think the aesthetics of the one piece is quite nice and traditional under a tree. I'd be interested in you views as the garden seat I made for that area has pitted much than others in sunnier spots.

 

[Jacob]

Thats interesting. I'm making a posh swing seat out of oak and the design is one solid piece of wood 60cm by 20cm by 3.5cm. its in a separate post. I was planning to leave it out all summer. It probably only has to last another 5 or so years as the youngest will be old by then, although we have big kids that like to loll on it. Would a slat design be better? I think the aesthetics of the one piece is quite nice and traditional under a tree. I'd be interested in you views as the garden seat I made for that area has pitted much than others in sunnier spots.

View attachment 136629

It's only a piece of wood - amortised over 5 years it won't break the bank!
But yes slatted would last longer in principle, depending on the details. That's why nearly all outdoor furniture is slatted.

 

[johnnyb]

in my experience wide boards are unavoidable for certain parts. I've learnt to make sure the cup is convex. the difference is quite marked. concave cup is constantly submerged convex is self draining.