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3 Way outdoor joint Answered

Hi I am looking at designing a garden structure which uses large timber sections and etched glass. I have a concept that I quite like but I am unsure about the best way to joint the uprights and joists. I want to try and keep the joints quite traditional and honest and reduce the reliance on glue.

I have attached a diagram of the end of one structure. Any help would be greatly appreciated. Thanks


Well, there are many ways but how thick is the glass? Do you intend to route out a channel for the glass to sit in or will you frame it out? Is this up high like a window or will it be used for deck railing? How traditional do you want it to look? Is this pressure treated wood or hardwood? Will you paint it afterwards? You can go with hidden fasteners and glue or do you want nails/screws? You can do traditional mortise/tenon/peg or lap joints or dovetail joints. Pocket hole or biscuit fastening. Outdoors and exposed to the elements will affect the shrinkage and expansion of the wood that you should account for. Depending on your skill or access to tools, there are several ways to do it. Good luck.

The glass will be recessed in to the wood and will stand six foot high, be 12 or 15mm toughened laminate and will be structural to the piece. I want it to look as traditional as possible and will construct using hardwood. There will be no painting but the wood may be lacquered or oiled I haven't yet decided. I was thinking of pegged mortise and tenons with as little glue (none) as possible but there might be a more interesting way than this.

I am a big fan of pocket-hole screws so you could plug up the holes with wood plugs. It is essential to have a mechanical fastener and something to bridge the joint but I understand your point of view of having the traditional look. Maybe dowels inside and locked together with hourglass shaped trim pieces on the outside. Use contrasting wood for the pegs or hole covers. I guess there are no additional trim pieces, moulding or embellishments to the wood frame.

That's correct minimal embellishments and zero mouldings to the frame. Contrasting wood is a nice idea, especially as I am considering a green oak frame. I'm not sure about the pocket-hole screws I feel that I should be able to get by without them... however this is just me being pedantic! It is something I will consider as I want the structure to be right.

I'm not massively knowledgeable about this kind of thing, but I think one of the characteristics of green oak frames is that they move and settle into shape - so I'm not sure you can mount the glass directly into the frame. Might be fine, if you leave a generous gap for the flexible sealant, and use deeper beading... Anyway, ignore this message if you know more about it than I do, but if not it might be worth looking up green oak + glazing. Have fun! Jethro

you could also hand cut a large dovetail if you've got a dovetailing saw (or a router, though, i'd imagine you'd want it to be bigger than most routers would allow)...instead of having either horizontal piece ride along the top of the upright, you would cut a dovetail the full height of the end of each horizontal (probably 1 to 2 inches long) then cut a matching slot in the upright portion. it would be a "traditional" look, and it would be extremely strong even without glue and if you wanted to, you'd be able to take the building down later with little effort

here's a picture in case that didn't make sense. this would be a top view of the joint i'm talking about. it's no where near any kind of scale, just illustrating what i'm talking about


Yeah I get the dovetail idea and it is something I had considered, I would however have to dovetail on (or lose) the slight horizontal overhang of the 180 degree beam. Deconstruction is always good to consider. The dovetails, I imagine, would have to be cut by hand i'm looking at 100 x 100 or 150 x 150 mm posts.

yeah, for structural stability they'd have to be pretty big dovetails so cutting by hand is probably the only way (though, i'd imagine that having hand cut dovetails on this thing would actually add to the "hand made" effect you're going for. no glue and no power tools)

i didn't actually take into account that the overhang was an actual design element (mahbad)....you could modify the dovetail even further.

cut square tenon into the top of the vertical piece, cut a square mortise into the horizontal that overhangs, then cut a dovetail into the horizontal with the overhang to accommodate the other horizontal. still no mechanical fasteners,  and still able to take it apart down the road.

basically any straight cut mortise/tenon setup or any kind of peg/biscuit conglomeration is  really going to require glue. the only way i could see using mortise/tenon is if they're keyed or if you pin them once they're in place with dowels so that they don't just pull back out.

if you wanted an overlap on both horizontals you could do a half lap and mortise/tenon combo. half lap the two horizontals where they meet the vertical, then cut a square tenon on the top of the vertical and a square mortise in both of the horizontals right in the center of the half lap. gravity should do the rest at that point (depending on what you're supporting with this thing), since there's a half lap with an overhang on both horizontals they'll be locked in and kept from sliding horizontally.

completely forgot some linkage http://sawdustmaking.com/woodjoints/dovetails.htm

Cheers, I have a dovetail template I made up a good few years ago for a school project knocking around somewhere... a tad small at about two inches though for this project. Its quite an elegant solution your suggesting , I like the combination of M&T's and dovetails with the ability to disassemble. I will (if I get the time try it to scale tomorrow. Thanks for the help, its been exceedingly useful.