Both doors and windows can suffer from sticking. The solution is often the same in both cases, so for easier reading we’ll just talk about doors here.
First of all check if the door is sticking at the top or bottom. The hinge might be loose or a screw head may be sticking out, so that the door isn’t hanging perfectly straight. If you can’t tighten the hinges properly, or if the screw holes are too big, you can replace the screws by longer or thicker ones with the same size head, or you can fill the screw hole with a matchstick. It’s also possible that the hinges may be worn. So if you fit new hinges you’ll probably find the door hangs straight again.

If the door sticks at the top, it isn’t always necessary to remove it. Sanding or planing away some of the wood is then often enough. You can also check if the door frame is still straight, and if the corner joints are still tight. It’s also possible that the lock or the strike plate on the door frame is sticking out a little. In that case, just make the recesses into which these components fit a bit deeper using a wood chisel.

Normally there’s a gap of about 6 mm between the door and the frame. To check this, insert a strip of wood with a thickness of 6 mm between the door and the frame on the same side as the hinges. Then you’ll be able to see how big the gap really is. If the gap isn’t big enough, draw a pencil line along the frame on the lock side of the door. Place the door on trestles and carefully plane or sand the edge of the door to the right size along the pencil line. Finish the door edge with paint or varnish.

If you’ve checked the hinges and joints and the door still sticks, the only solution is to saw or plane the height to the right size. Remove the door by tapping out the hinge pins using a hammer and a punch. Place the door against the frame on a wood strip with a thickness of 2 mm, and then check if the top and edges of the door are parallel with the frame and at an even distance from it. If that isn’t the case, mark out the places on the door where you need to plane or sand it down slightly.

If the door itself has sagged so it’s no longer straight and square, you can reinforce it with corner brackets. Remove the door by tapping out the hinge pins using a hammer and a punch. Place the door against the frame on small wooden wedges and position it so that it is parallel with the frame and at right-angles to it. Assuming that the door frame is straight, you can now fit corner brackets to the door. Find the right positions for the 4 brackets and mark them out. Make the recesses for the brackets with a wood chisel or an electric router. Paint the brackets (if they are not galvanized) with corrosion-resistant paint. Fill the recesses with 2-component adhesive and fix the brackets in place with wood screws. After drying sand the areas around the brackets smooth, fill flush with the door surface using wood filler and finish with matching pain.

• If the bottom of the door just sticks slightly, you can insert a piece of coarse sandpaper (if necessary on top of a plank or a wood strip of the right thickness) under the door. Then just open and close the door a few times over the sandpaper and it won’t stick any more.
• If you’re replacing the hinges of a door or window that opens outwards, you could consider fitting security hinges. These have a special ant-burglary pin, so even if burglars remove the hinge pin they still won’t be able to take the door or window out of the frame.