Repairing a roof

Summary: Learn how to make repairs to a roof, replace a plain roof tile, replace a group of tiles, replace a slate tile, replace a ridge and hip tile, replace wood shingle, replace asphalt shingle, repair a roof valley, repair verges and make repairs to a flat roof.

Common roofing defects include broken or missing tiles and damage to a roof valley caused by general wear and tear or storm damage. Minor repairs can be carried out with the aid of a helper providing that you work safely, but if the roof is badly damaged and requires large-scale repairs it may be advisable to call on a professional roofer.

Cut a piece of self-adhesive flashing strip and smooth it down with a seam roller.

Temporary repairs

To fix a leak or make a temporary repair whilst you locate replacement roof materials, follow one of these methods:

  • Cover small cracks with a sheet of cooking foil or roofing felt sandwiched between 2 layers of mastic or roof sealant.
  • For larger cracks and holes, use flashing strip. Prop up the tiles in the course above the broken one using wedges.
  • Clean the surface with a wire brush and apply flashing strip primer to the same width as the flashing strip.
  • Cut a piece of self-adhesive flashing strip to cover the crack, peel away the backing and smooth it down with a seam roller.
To replace a single broken roof tile use wedges to lift the tiles either side of it. Tilt the tile to remove it from the interlocking tiles.

Replacing plain roof tiles

  • To replace a single broken roof tile slide up the tiles onto your broken tile. Alternatively, in the course above the broken tile use wedges to lift the tiles either side of it.
  • Tilt the tile to remove it from the interlocking tiles.
  • If a tile is nailed to a batten, use a slate ripper to cut through the nails. If it is held in place by clips, simply levering the tile up should release it.
  • Lower the broken tile to the ground in a bucket on a rope.
  • Slide the new tile up into place. It is not necessary to nail or clip it in place.
  • Reposition any tiles you moved and remove any wedges.



To replace a single broken roof tile use wedges to lift the tiles either side of it. Tilt the tile to remove it from the interlocking tiles.

Replacing a group of tiles

  • First lift the course directly above the highest row to be replaced, pushing wedges under them to expose the course below.
  • Remove the old tiles one by one, sliding a trowel under the tile’s lower edge and lifting so its nibs clear the batten. If the tile is nailed to the batten, rock it back and forth to free it. If this does not work, slide a slate ripper under the tile, hook the nail in one of its barbs and pull it forward sharply. This should cut through the nail.
  • Carefully lower the old tiles to the ground in a bucket attached to the end of a rope.
  • Having removed all the old tiles, start fitting the new tile on the bottom course first and work your way up the roof working from right to left. Hook the new nibs of the new tiles over the battens.
  • As you proceed up the roof, the tile you are fitting should be centred over the join between the two tiles directly below it.
  • Nail the tiles in every 3rd course to the battens with 2 clout nails.
  • On reaching the final course of new tiles, push wedges underneath the bottom edges of two adjoining tiles in the course above and with the new tile on a trowel, slide it into position.
  • Work along the row in this manner until all the tiles have been replaced.
Nail the top end of a metal strip over the exposed gap beneath where the new slate will go.
Position the new slate ensuring it fits. Bend the strip of metal up and over the bottom of the slate, securing it in position.

Replacing slates

  • To remove a damaged slate, cut away nails with a slate ripper or hacksaw blade. Wind tape around the handle end of the hacksaw blade to prevent it cutting into your hand. Also, wear work gloves to avoid grazing your knuckles on the roof when sawing.
  • Pull the broken slate towards you, working it free from the overlapping slates.
  • Lower the broken slates to the ground in a bucket on a rope.
  • Nail the top end of a metal strip over the exposed gap beneath where the new slate will go.
  • Position the new slate ensuring it fits and its lower edge is in line with the surrounding slates.
  • Bend the strip of metal up and over the bottom of the slate, securing it in position.
  • To replace multiple slates, remove the uppermost slates first and work down.
  • First fix the bottom courses of slates with nails to the exposed battens, placing them with bevelled edges facing up.
  • To fix the top course, fix the slates with a metal strip, as described above.

If the repair requires you to cut a slate follow this method:

  • Place the slate tile flat on a board and use a tile spike and metal rule to score a straight cutting line.
  • Position a wide bolster on the cutting line and tap gently with a hammer.
  • Alternatively position the slate flat on a table with the scored line addressed to the table edge. Press down to break the slate cleanly along the scored line.
On the roof, apply a bed of mortar on both sides of the ridge or hip. A gap must be maintained under the ridge for air to circulate which keeps the roof timber dry.

Replacing ridge and hip tiles

Ridge tiles cover the gap where the two sloping roof surfaces meet at the apex. Hip tiles join the line of a course of tiles or hip where two roof slopes come together.

  • Remove loose mortar with a cold chisel and club hammer.
  • Remove any loose or damaged tiles and brush away dust and debris from the area.
  • Mix up the mortar: 1 part cement to four parts sharp sand. Adding some PVA solution to the water will improve the bonding of the mix. The manufacturer’s instructions will give the correct amount to be added. Mix up enough mortar to half fill a bucket, remember that a stiffer mix is easier to work with.
  • Before climbing back on to the roof wet the ridge tiles with water.
  • Wet the roof area to be repaired with water to prevent the mortar from drying out too quickly and cracking. Then brush PVA solution over the area to aid adhesion.
  • On the roof, apply a bed of mortar on both sides of the ridge or hip with a brick trowel. The mortar should cover the areas where the bottom edges of the tile will rest. A gap must be maintained under the ridge for air to circulate which keeps the roof timber dry.
  • Carefully position the ridge tile in place. Check that the bottom edge of the tile forms a smooth line with the tiles either side of it.
  • Point the tile with mortar using a pointing trowel, filling in joints to ensure no water will penetrate.
  • Use a brush to neaten the mortar and smooth it over.
To help you access tricky angles, disengage the hacksaw blade from its frame and use it by itself.

Replacing wood shingle

  • Use a hammer and chisel to remove damaged shingle.
  • Cut through the shingle’s fixings with a hacksaw. To help you access tricky angles, disengage the blade from its frame and use it by itself. You will need to cover the end with strong tape and wear heavy-duty work gloves.
  • Place the new shingle in the recess and fix it in place with nails hammered as close as possible to the row above.
  • Apply silicone sealant to the edges of the shingle and over the nail heads



Loosen the fixings of the strip of shingles above so that you can slide the new one underneath with ease.

Asphalt shingle

  • Remove the damaged strip by levering it up with a crowbar.
  • Loosen the fixings of the strip of shingles above so that you can slide the new one underneath with ease.
  • Fix the shingle securely, recessing nails with a hammer.






Apply flashing-strip primer with a paintbrush and leave to dry for half an hour.

Repairing a roof valley

A roof valley is found where two sloping roofs meet, channelling water to the gutters.  A valley can be made from various materials, often lead or another metal, but sometimes also plastic or tile. The method for repairing a valley will vary according to the roofing materials. Below are repair guidelines for fixing cracks in metal valleys.

For fine cracks or temporary repairs, use liquid bitumen compound to seal the area:

  • Clean the area with a wire brush. You will need to enlarge the repair area by at least 50mm (2in) beyond the crack.
  • Apply roof-and-gutter sealant on the crack and around the area.
  • Cut out a patch of roofing felt (or kitchen foil) and stick it over the area.
  • Apply more sealant over the top.
  • Paint liquid bitumen waterproofing solution over the area with strokes in one direction, using a soft brush moistened with water. Use an old paintbrush as you will have to throw it away afterwards.

For holes or large-scale corrosion, patch the damage with flashing strip:

  • Clean the area with a wire brush. You will need to enlarge the repair area by at least 50mm (2in) beyond the crack.
  • Rub over the area with sandpaper, and wipe clean.
  • Apply flashing-strip primer with a paintbrush and leave to dry for half an hour.
  • Cut a piece of flashing strip to extend 50mm (2in) beyond the damage and peel off the backing strip.
  • Smooth the strip down with a seam roller.

Repairing verges

When the mortar sealing the edge of the tiles on the roof verge is damaged leaks can occur.

  • Remove loose mortar with a cold chisel and club hammer.
  • Remove all dust and dampen the area with water and brush on some PVA bonding agent.
  • Mix up your mortar (see above) and butter the mortar firmly along the edge of the tiles with a brick trowel, ensuring there are no air pockets in it.
  • Smooth the edges and clean away any excess, leaving no ridges that may hold rainwater.
Apply primer over the hole and extend it out over the surrounding area.

Flat roof repairs

To patch a hole in a flat roof, you can purchase a patching kit, which will include a specialist roofing primer. The instructions may vary from brand to brand so follow the manufacturer’s guidelines carefully.

  • Dust the surface clean.
  • Apply primer over the hole and extend it out over the surrounding area.
  • Cut a self-adhesive patch to size, and peel off the backing strip.
  • Position the patch and smooth it over with a seam roller.

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