If you're constructing a new fence with a gated opening, put up the gate and posts first and build the fence from them. If you're replacing an old gate, make sure you measure up accurately to get the exact size you need. It's worth taking a tape measure with you when you buy your new gate, as they're sold in both metric and imperial sizes and the conversions aren't always accurate. Last but not least, think about which way you want your gate to open (most open into a property rather than out).
Gateposts for light gates should be about 100mm square and 610mm longer than the gate's height. For heavier gates (over 1.2m high or wide) the posts should be thicker and at least 760mm longer than the gate height. It's always best to check the manufacturer's specifications.
You'll need to treat wooden gateposts with preservative before you install them and set them in concrete as post spikes don't give enough support. Where possible, try and choose fittings that have been japanned (lacquered) or galvanised to stop them rusting.
With some hinges, you may find there's some movement or 'play' when you try to screw them to the gate. This makes them difficult to position accurately. If this is the case, you'll need to adjust them after the posts are set. This will be easier if you fit only two holding screws per hinge into the post while it's still lying flat. It's best to wait until you've hung your gate before you fit the latch.
If your gate posts haven't been weathered, you'll need to cut the top to a slant so that rainwater can run off. Try to do this first, using a sliding bevel to mark a 20 degree angle from the top of the post.
Continue the line square down the face of the post and saw neatly along it. Then paint the cut edge with wood preservative. If the wood is untreated, you'll need to paint the whole post.
When you've decided which way you want your gate to open, lay it face down on level ground. Place the posts either side with their tops 50mm higher than the top of the gate and leave a 5mm gap either side of the gate so it can open and close freely. Use two timber lengths to raise the gate slightly, so it sits in line with the gateposts. You can adjust this as necessary with timber off-cuts or wedges.
Place the hinges into position on the back of the gate. Mark the screw positions and drill one pilot hole. Test it by driving in a screw to check the drill bit is not too large, then drill the remaining pilot holes.
Next, screw the hinges in place using galvanised screws. If you find it tricky to position them accurately on the post, wait to fit them and the latch until you've hung the gate.
Drill pilot holes for the latch screws, then screw the latch into place. Don't forget to allow a 5mm gap between gate and post when doing this.
Brace the gate and posts with three lengths of timber to make sure the construction is solid. Use the braced gate to mark the position of the post holes.
Use a spade or post-hole borer to dig your post holes roughly a spade and a half wide and deep enough to leave a 50mm clearance gap beneath the gate so it can open freely.
You can check this is enough by laying a spirit level on the ground where the gate will open and level the ground if you need to. In soft ground you'll need to dig a trench between the post holes about 300mm wide and 200mm deep and fill it in with concrete.
This will help stop the posts from being pulled inwards by the weight of the gate. Lower the gateposts into the holes, using a spirit level to check they're in line.
Use timber props to hold your gate and posts in position. Mix the concrete, then concrete the posts into the ground. Remember to slope the surface downwards to direct rainwater away from the wood.
Let the concrete set for 48 hours before you remove the props and brace.
If you need to fix your gate to a wall, it's a good idea to secure the first post using expanding masonry bolts. Their expanding section fits into a drilled hole in the masonry. You can then fit the post over the stud and tighten the nut, which makes the section expand and grip the sides of the hole.
Use three fittings for a post that's 1.2m or higher and two for anything less. First, use a flat wood bit to drill recesses in the post just deep enough for the nuts and wide enough to allow access for a socket spanner. Then change your drill bit and drill clearance holes for the studs right through the timber.
Take a long masonry bit of the same diameter and, holding the post against the wall, drill pilot holes into the masonry. You'll need to be accurate or the bolts won't work.
Take off the post and enlarge the holes in the wall, using a masonry bit the same size as the expanding section. Insert the expanding section in the wall and hang the post on the studs. Finally, put the washers and nuts on the ends and tighten them with a socket spanner, taking care not to over-tighten them.