I need to replace a gate and want something smarter than a treated softwood one so am looking for advice on what timber to use. I found a picture of exactly the sort of thing that I had in mind here:
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is obviously oak, but would I use green or seasoned oak to make something like this? I've never made anything that would be exposed to the weather like this
- presumably I need to worry more about the expansion and contraction of the wood. If I used 6" wide seasoned planks for the front face of the gate is it going to expand and deform/split when it gets wet?. Any advice greatly received or ideas of a book that might help me with this.
Sweet chestnut is good, if you're in the right part of the country.
Oak is good too, but it makes for a heavy gate. It also needs more effort to cut mortices. Easier if you work it green. Remember that oak will stain with iron, so use stainless fittings, bronze nails, and shim beneath hinge plates with plastic. Otherwise let it darken.
Probably the best all round is larch. Try to avoid any that looks like it's thinking of twisting. Some trees are more resinous than others, and they'll be the best lasting. You can use any junk for the boards, but try and select good stuff for the frame.
Douglas fir is easiest to find, but not terribly rot-resistant. Larch is better, and otherwise similar.
long as you have adequate hinges, then the design is easier. For a door like this, then just use three decent-sized hinges. Really a ledged and braced door like this ought to be the other way round anyway - put those diagonals into tension, not compression.
The difficulty with gates is that they're a long cantilever (i.e. they stick out, and they're only supported from one end), so structural design of them is non-trivial. If you're designing a wide gate then think of it as a triangle rather than a rectangle - the forces are largely that diagonal tension hanging down from the upper hinge, the rectangle is just a filler panel. This is why it's good to place the top hinge as high as possible, and to have an upstand above the main gate at the hinge end, a bit like this:
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really that top hinge ought to be mounted higher, above the top rail. The main load is (or should be) in the diagonal, not the rail.
In general, what you can get most easily. Although oak will likely be over-priced unless you're dealing with somewhere that will have both, then you can go for green and it will be less trouble to work it. One of Aldi's bargain morticers would help.
Of course it will expand. It will do this because it becomes wet, no matter how much you dried it beforehand. You don't even need to get it "wet", just UK winter humidity will expand it. Read Hoadley's book "Understanding Wood" or else the US Forest Products handbook to get chapter on verse on all this. Shrinkage and expansion is accurately predictable if you do the numbers. Unless it's "seasoned" for a decade of cycles, then "dried" timber still keeps moving, it's just in a different state when you first get it.
Generally though, wood shrinks 10% worst case from wet, or else expands 10% from fully dry. It does this axially and circumferentially, and not at all lengthways. For any more detail, read Hoadley.
So carpentry for outdoor timber has to deal with this expansion. Forget trying to fasten everything rigidly, it's not going to happen. Be cautious anywhere near cross-grain joints (one piece shifts one way, the other goes at right angles). Be cautious of butted long-grain edges, as they're going to add the expansion of individual boards into expansion of the whole door, causing it to stick. Try and absorb expansion of individual pieces by how you arrange or joint that one piece, before it combines up into several movement's worth. Traditional designs, so long as they're reproduced accurately, are usually the way they are so that they cope with this.
A simple approach is the ledged and braced door, as your picture. This uses a Z-shaped structure of lengthways members (not expanding lengthways) with vertical shiplapped boards to fill the hole. The expansion is in the boards going sideways, so each board is nailed once in the centre of it (i.e. three times over its length, but only once per width) and it will expand and contract individually. The lap between boards absorbs this seasonal movement and the overall door remains the same size. Shiplapping (just overlaying board edges) is most common, but looks a bit cheap. Better is to plane a half- thickness rebate into the edge of each board ("up" and "down" on each edge) and keep the boards fastened flat. The tool for this is a Stanley #78 rebate plane, which you'll find on eBay. You can't do it easily with a router, unless you have a big one in a table that can cut a wide shallow rebate safely. When you set the boards, remember to leave this expansion space (i.e. don't butt the rebates tight). Leave about 5% gap (of board width) at the edge of each rabbet, or less if you actually read Hoadley and do the numbers.
When making a ledged & braced door, the question is how to join the diagonal braces into the horizontal ledgers. Butting is popular, but gives a weak, flexible door. Best approach (for practical simplicity) is a half-lap joint, then pegging it with wooden pegs - or screws (don't nail the frame - peg or screw it. Nails are just for hanging ther infill panels on.) Assemble the ledged frame flat on the ground, pin a couple of battens on the vertical edges to hold it in place, then drill through both halves of the joint. Take a treenail (square oak or hard hardwood strip, just bigger than the hole diameter, shave one end to a round point and then drive it into the hole with a mallet. Saw the ends off flush. Decoratively, the diagonal is often thinner and lapped beneath the ledgers at both ends.
More sophisticated doors use joinery, not carpentry. Joinery is the high-tech medieval approach of "joining" panels, without them then splitting with seasonal shifts (it's where the distinction in job roles comes from). You make a more complicated structure on a bench, with cut joints, rather than assembling unsquared beams on site (the other role distinction). Joinery's basics are to make a rigid structure of these long members (no expansion lengthways) with joints between, then to fill in the holes with loosely placed boards that are free to move. You'll get a more solid door this way, but it's much more work. This is where the well-known six-panel door comes from, but you'll be cutting a lot of mortices to make the frame. Twisty in larch, hard graft in oak. Depends how much effort / result you want. If you're going this far, read some books first.
Good books on this topic are old mid-century handbooks of carpentry, especially Charles Hayward's series (eBay again).
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.
Thanks for the extremely comprehensive reply. You're right I meant door not gate.
Just a few more questi> >> I need to replace a gate and want something smarter than a treated
I'm in Hampshire. I know that the local sawmill does occasionally have some chestnut so will have to make a visit.
Do you know any good online suppliers of bronze nails? I've never seen them around here.
here:
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What the reasoning behind? Is there an advantage to them being in tension?
I've never worked with green oak before is it much easier to work with than seasoned?
I've got a morticer and router in a table so the joints and rebates for the planks on the front of the gate shouldn't be too much of a problem especially if green oak is easier to work with than seasoned.
I was slightly confused by this description. I was planning to use mortice and tenon joints to join the verticals to the the horizontals then just butting the diagonals in and nailing the planks to the front.
I understand how a half lap joint would be an improvement for the diagonals, but won't it interfere with the mortice and tenon?
I like the idea of using wooden pegs - I'll have to experiment.
Boat chandlers. I get mine from Robbins in Bristol. They're not cheap though! Stainless is cheaper, but I do like the look of bronze with oak. Mostly (I'm doing indoor furniture) I actually use cheap copper roofing nails as rivets in drilled holes through fumed oak.
It's arguable. Mostly an issue for big stuff anyway, so a garden gate or door is neither here nor there. Theoretically it's stronger with tension, but there's also an argument that comprssion will tend to close a joint up if it works loose, rather than pulling apart. You can also make a door with three ledgers so that it has M shaped bracing, which can look good.
Not much different with power tools, but you'll notice it if you're hand-chiselling.
So where are your verticals? In a purely ledged & braced door there aren't any, just the horizontals and the diagonals. The cladding is merely a cladding, not part of the joinery. Without the diagonal braces it would of course be a non-rigid parallelogram, which is why the form with diagonals is actually easier to make. Otherwise you have to do something with the vertical cladding that's both rigid, and capable of handling moisture expansion.
I wouldn't use mortice & tenon joints at all. For a more complex door (shed or garage rather than garden wall) I would do this with a rectangular frame. Then I would mortice and tenon the uprights and horizontals, but probably still lay the diagonals on from "inside" (under the cladding) with half-laps. I'd make them two-thirds of the outer frame's thickness, so that's half-laps on the diagonals and one-third on the main members.
There's a lot of experiment needed there, to know how much oversize is right to drive in securely, but without risk of splitting.
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