A Look at Flat Roof Repairs and Your Options

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This page contains a troubleshooting guide for leaky flat roofs that are leaking and are in need of a repair.

Our guide is intended for anyone who is competent with a ladder and roof safety such as tradespeople and some experienced DIYers.

We will cover the following:

  • quick fix repairs you can use to keep the flat roof watertight until a longer term solution can be applied.
  • long term fixes without replacing the entire roof.
  • examples of when you really need to bite the bullet and replace the flat roof.

As we are sure you can appreciate, there are many different types of flat roof materials and therefore different solutions will apply.

We will try to cover the most common types of materials that are in use on flat roofs in the United Kingdom.

The General Rule of Thumb

As a general guide, you can repair most flat roofs if:

  • the leak is caused by an impact such as a slipped tile, a tree branch or the like
  • the leak is caused by a one-off hole, tear or localised issue that is isolated and not indicative of a more widespread issue

You are probably wasting your time and money trying to patch repair a flat roof that is:

  • very old and has leaks in multiple places
  • that is bowing, dipping, bending or buckling between the joists
  • where the entire surface has deteriorated due to age or UV damage

Of course, many people do carry out patch repairs on such roofs, but they are doing so at great risk.

Because these roofs are flat they often hold water, especially during spells of heavy rain, thus a small tear or hole could cause a significant amount of water to enter the property. Certainly more so than a pitched tiled roof with a similar sized hole.

Common Issues and Things to Look For

Regardless of the type of flat roof material that is used, leaks are often:

  • located near a join or seam
  • where the felt has pulled free from the vertical wall
  • caused by the failure of the supporting timber decking underneath
  • made worse by water discharging onto the roof from a rainwater pipe
  • made worse by water pooling on the roof when it should ideally discharge off the roof
  1. check where the felt has been inserted into the wall, thermal movement may pull the felt out of the brickwork.
  2. check all seams/joins near any leaks, if the felt hasn’t adhered sufficiently it may allow water to a pass through.
  3. can the rainwater pipe be relocated or an additional pipe laid across the flat roof to minimise the amount water (and thus wear and tear) on the roof?