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Flat Roof Repair or Replace? How to Decide

By Staff4dshire Group · Staff4dshire Roofing Specialists

A leaking flat roof does not always need replacing, but patching one that has reached the end of its life is money wasted. The decision comes down to what has failed, how widespread it is and what condition the structure underneath is in.

Torch-on felt flat roof replacement

When a repair makes sense

If the problem is local and the rest of the covering is sound, a repair is usually the right answer. Typical examples are a split at a joint, a failed upstand where the roof meets a wall, a damaged trim or a blocked or poorly sealed outlet.

A good repair deals with the cause, not just the wet patch. Water travels under coverings, so the leak inside is often some distance from the defect on the roof.

Signs it is time to replace

Widespread cracking, blistering or crazing across the surface, repeated leaks in different places, ponding water that sits for days, and felt that has lost its mineral finish are all signs the covering is worn out.

Soft or springy areas when you walk on it are more serious, because they point to a wet or rotten deck. At that stage the boards, and sometimes the joists, need replacing, and laying a new covering on top would trap the problem.

New EPDM rubber flat roof on a garage

The deck and the falls

A flat roof is only as good as what is under it. We check the deck for rot and movement, and the falls for how quickly water runs off. Firrings can be added to improve falls when the roof is replaced, which reduces ponding and extends the life of the new covering.

If you are replacing more than a quarter of the roof, Building Regulations usually expect the insulation to be upgraded where that is practical. Converting to a warm roof, with insulation above the deck, is often the neatest way to do it.

Choosing the new covering

The three systems we install most are EPDM rubber, GRP fibreglass and torch-on mineral felt. Each has its strengths; our EPDM vs GRP vs felt guide explains the differences.

Whatever the system, the details make the roof: trims, upstands, abutments and outlets. See Staff4dshire Roofing Specialists, or our local pages for flat roofing in Rugeley and flat roofing in Cannock.

Quick checklist

  • Note where and when the leak appears
  • Look for splits, blisters and ponding
  • Check for soft or springy areas
  • Check the edges, upstands and outlets
  • Ask whether the deck needs replacing
  • Ask about insulation and a warm roof

Frequently asked questions

Can a flat roof be repaired in wet weather?

Temporary repairs can sometimes be made, but most permanent repairs and new coverings need dry conditions to bond properly.

Can you lay a new flat roof over the old one?

Sometimes, but usually we strip it so the deck can be checked. Overlaying a failed roof can trap moisture and shorten the new roof's life.

How do I know if the deck is rotten?

Soft or springy areas underfoot, sagging and staining on the ceiling below are common signs. We check the deck before quoting.

About Staff4dshire Group. Staff4dshire Group is based at Unit 7 & 8 Kimberley Business Park, Rugeley, Staffordshire. Our companies cover building and landscaping (Staff4dshire Properties), roofing (Staff4dshire Roofing Specialists), scaffolding (Staff4dshire Scaffolding), groundworks, drainage and utilities (Staff4dshire Groundworks & Utilities), plant hire (Staff4dshire Plant Hire) and renewables (Margav Energy). We work for homeowners, developers, principal contractors and local authorities across Staffordshire, Birmingham and the West Midlands, and we are a registered supplier with Walsall, Tamworth, Sandwell, Dudley, Birmingham, Telford & Wrekin, Wakefield and Bradford councils.
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