How To Repair Garage Doors

Garage doors suffer from all the problems that normally affect house doors, but their weight and exposed position means that these often set in earlier than usual, so knowing how to repair garage doors is a real money saver. So keep a close eye open for deterioration and deal with it quickly to avoid having to buy costly replacements.


If a garage door frame is faulty, weak, or damaged by rot, the weight of the doors is likely to cause splintering — especially around the hinges.

If this happens, you need to cut the frame away slightly above the damaged section at an angle of 45° and replace it with timber of the same size. If there is a door stop on the frame, you need to add this with a second, smaller strip of wood. Saw through the old joints as How To Repair Garage Doorscleanly as possible because it will not be easy to trim afterwards.

1. With the damaged section removed, stand the new timber alongside the jamb and mark the position of the angled joint. Cut it carefully, slightly oversized, then trim it gradually with a plane trying it in place until you are happy with the fit. Paint all the sides — especially the back — with primer.

2. Use a cold chisel to rake out the mortar joints in the masonry behind the frame in two places, one near the bottom of the jamb and the other near the new joint. Then cut two tapered wooden plugs, about 50mm wide and as long as you can jam into the cracks you have made. Drive them into the raked out joints.

Cut off the plugs in line with the back of the jamb. Try the new timber in place, using a straightedge to check that it is in line with the old.

Drill through the angled joint for screws and apply waterproof adhesive to the two ends before putting the new section in place.

Hold it firmly by nailing it into the plugs. Screw the joint together using rustproofed screws.

Finally, paint the new timber to protect it from exposure.


Hinges tend to be weak spots —either because they rust through, or because rain sets in and rusts the screws securing them. The best cure is usually to fit new ones.

Butt hinges are not suitable for such large doors, and teehinges tire rarely strong enough. By far the best type are bands and hooks. These are made in sizes large enough for the heaviest door and fitting them is straightforward. There are two sorts —cranked and straight — depending a great deal on how your door is fitted.

  • Support the door, then take off the existing hinges. If you can’t undo the screws, drill them out.
  • Wedge the door in place in the opening, hold the hinge against the door, and mark the position of the hook on the door jamb.
  • If the band is straight, the hook will have to be let into the jamb; if the band is cranked, the hook is screwed directly onto the jamb.
  • In either case, a small hollow will have to be cut into the wood to take the rivet in the end of the band which projects at the back.
  • The easiest way to mark the position of the rivet is to put the band in place and strike it sharply with a hammer.
  • Use screws at least 38mm long to fix the hook, then hang the band on it to mark the positions of the fixings on the door. The band is held by screws, plus a bolt which goes through it at the hanging end.

1. Before drilling the bolt hole hang the door using two screws in each hinge. Check that it opens and closes easily.

2. When all is well, drill the bolt holes right through the door and bolt the hinges in place with coach bolts. Make sure that the square section under the head of each bolt fits into the square hole in the hinge.

Finally, give the hinges a coat of rustinhibiting primer before painting them to match the door.


Large, heavy garage doors often sag simply because of their own weight and width. The cure is to strengthen the joints in the frame, after putting the door straight again.

  • Take the door off its hinges and set it up on a bench or trestles so that it can be squared up properly.
  • The ideal tool for the job is a large sash clamp, but if you don’t have one of these you can very easily do the job with a homebuilt clamp. Make this out of a piece of 50mm X25mm timber about 200mm longer than the width of the doors, plus a couple of pieces of 75mm x 50mm softwood about 150mm long.
  • Screw the blocks to the 50mm x 25mm batten so that they span the door with about 40mm to spare. Cut two wedges by sawing diagonally across another piece of timber about 50mm X 50mm and 150mm long. Using two hammers, drive the wedges into the space between the blocks and the door to pull the frame up tight. As you do this, check periodically that the door is square.
  • Clamping joints will loosen the old wedges in the tenons. Drive a small chisel down the side of each wedge to make a rectangular hole, then hammer in a new wedge split from a piece of hardwood.
  • Next, drill into the stile and straight through each tenon using a 9mm drill bit. Drive a glued 9mm dowel into each joint Make a rectangular hole with o chisel to take the new wedges —if they stand proud when driven home, chop them flush with a sharp chisel and sand smooth.
  • When all the existing joints have been tightened and locked you can give them additional strength by screwing metal angle plates across them. To be effective these plates have to be at least 225mm along each leg; fit an Lshaped one at each corner and a T shaped one on the middle rail.
  • Make sure that you fit the plates on the inside of the doors, otherwise the rain may penetrate behind them and cause the timber to rot.
  • The plates will look less obtrusive if you recess them into the wood. With the door still clamped, put each plate in position and mark round it with a trimming knife. Chisel out a recess deep enough for each plate to fit flush with the wood, then drill holes and screw the plate in place.
  • Remember that strengthening the joints may cause the paint around them to crack. Be sure to rub down and repaint these sections before refitting the door to the frame.


If the warp is severe, there is little than can be done to straighten it because timber exerts a tremendous power when it twists or bends. But if the warp isn’t too serious, it may be worth trying to add an extra brace. This should run from the bottom of the hanging side to the top of the opening side — but note that it might add even more weight to an already very heavy door, causing further problems itself.

There are two choices — a metal brace or a wooden one. The advantage of metal is that it is less obtrusive.

If you decide to fit a metal brace use a mild steel bar about 6mm thick, and between 25mm and 50mm wide. It should be just less than the diagonal measurement of the door and drilled to take 9mm coach bolts.

Some ironmongers and steel stockists will make such an item to order; otherwise you will have to buy a plain bar and drill it.

  • To do this, start by holding the bar diagonally across the door to mark the bolt holes where it crosses the frame at each end and the brace in the centre.
  • Drill pilot holes first with a 2. 5mm3mm twist bit, then drill the final bolt holes using a 9mm bit. If you are using a power drill, put it on a low speed setting and lubricate the bit with oil as you drill. Secure the bar with 9mm coach bolts.
  • For a wooden brace, use timber at least 38mm thick and 75mm wide.
  • As timber tends to bend ll1P \ towards its softest side, if the top of the door is bent outwards put the heart side of the brace (where the grain is concave) against the door.
  • For an extra bit of push in the centre, put a thin packing under the brace — packing under the brace at the top and bottom rail will give on extra bit of pull. If using a wooden brace, remember timber tends to bend towards its softest side.


Large, side-hung double garage doors take a great deal of punishment from the weather. The bottom rail, the base of the stile and the bottom of the matchboarding are the most vulnerable areas because rainwater runs down the face of the door and into the joints.

If rot does set in, you must remove and replace the affected parts. If the rest of the door is in good condition, this is probably worth doing. But bear in mind that you’ll have to take the door off its hinges — and remember it is very heavy — remove any glass panels and support it on a bench or trestles while you carry out the repairs.

Depending on the extent of the damage, you may have to renew part of one stile, the entire bottom rail and possibly part of the existing matchboarding. If any more than this is rotten —say, if both stiles have gone —the door isn’t worth repairing. 1. Before you remove any of the damaged areas, make up a replacement piece for the stile. This should be cut from timber of the same dimensions, slightly longer than the damaged area. And you’ll find it easier when it comes to making the mortise and tenon joint if the bottom of the new stile section is slightly oversize. Cut one end of the new section at an angle of 45°.

2. Clamp the new section on top of the existing one and mark the 45° angle on the original together with the position of the mortise on the new one.

3. Cut a new bottom rail as long as the old one, including both tenons. Place this over the rail, and mark where it meets both stiles — this will give you the tenon shoulder positions.

To remove the damaged areas, saw through the old stile at the 45° angle marked, and cut any rotten matchboarding at a point where there is something solid behind to fix the new boards to. This may be half way across the brace or central rail, depending on how far up the rot has spread.

Lastly, remove the old bottom rail from the stile. Clean off the paint in the area of the joint to find the wooden or metal fixing pin. Drill or punch this out, cut through the shoulder of the old joint and drill or chisel out the remains of the tenon.

The new rail must be attached to the stiles in the same way as the original via a mortise and tenon joint at either end. Mark this carefully to match the original. Cut the tenon with a saw and finish with a chisel. To make a new mortise, drill a series of holes to remove the bulk of the waste wood; remove the remainder with a chisel. 4. Try the new mortise and tenon joints for fit before applying a waterproof woodworking adhesive (such as Cascamite) and fitting the bottom rail into the good stile. Glue the replacement section of stile to the other end and push it into place against the old stile.

To hold the rail in position while the glue dries, clamp the whole assembly together with a sash clamp. If you don’t have one, hold the joints with dowels; you must drill the holes for these before gluing the joints. Drill a 9mm hole straight through the sides of the mortises. Put the joints together and mark the tenons through the holes.

Take the joints apart and drill 9mm holes through the tenons, setting the point of the bit 1mm nearer to the shoulder of the tenons than the marks you made.

When you glue and assemble the parts, drive 9mm dowel through the holes: then the off centre holes will pull the joints up tightly.

5. With the bottom rail in position glue and screw the angled stile joint together, making sure the screws are inserted through the thick end of each section.

Cut the new matchboarding and nail it in position. You should use nails long enough to protrude about 8mm then bend over the points and punch them into the wood.

6. Finally, cut the excess off the bottom of the new stile section to make the stile flush with the bottom rail, then prime and paint the new wood as soon as possible to prevent rot.

Leave a Comment