Flat Roof Repair & Replacement Costs in Dublin

What affects the cost of flat roof work?

Main factors

• Size of the roof, and how much of it is edge, upstand and detail rather than open area
• The existing system — felt, GRP/fibreglass, EPDM, liquid or an older built-up covering
• Condition of the deck beneath, which can only be confirmed once the covering is opened up
• Drainage: falls, outlets, gutters and whether water is ponding
• Upstands, kerbs and abutments where the flat roof meets a wall
• Penetrations — soil vents, flues, roof lights and pipework
• Edge detailing, trims and how the roof meets adjoining coverings
• Insulation, where it is being renewed or upgraded as part of the work
• Access to the roof, including through or over the property
• Removal and disposal of the old covering on a replacement

Repair or replacement on a flat roof

A localised split, a failed lap, a lifted trim or a defective outlet on an otherwise sound covering is usually repairable, and repairing it promptly is by far the cheaper outcome.

Replacement moves into view where the covering has multiple failures, where the surface has degraded generally, where water has been getting in long enough to affect the deck, or where the falls are so poor that the roof holds water permanently. Patching a saturated deck simply moves the problem along.

Why the deck condition matters so much

Most domestic flat roofs in Dublin are timber decked. Once water has been sitting in the build-up, the boards soften, fixings lose their grip and any new covering laid over the top is being installed on an unsound base.

This is one of the most common reasons a flat roof price changes between a first conversation and a final quotation. We check what we can before quoting, and where deck condition is uncertain we say so explicitly rather than leaving it to be discovered.

How the system chosen affects the price

Vantage Roofing works with felt, GRP/fibreglass, EPDM and liquid roofing systems. They are installed differently, they detail differently, and they suit different roofs. No one system is appropriate for every flat roof — shape, penetrations, upstand heights, access and how the roof will be used all feed into the decision.

The cost difference between systems on a given roof is usually smaller than the cost difference caused by the deck, drainage and detailing. Choosing a system because it is cheapest, on a roof it does not suit, tends to be the expensive route. Our flat roof types guide compares the systems, and felt vs fibreglass looks at the two most commonly compared.

Drainage, falls and ponding water

A flat roof is not flat: it should fall towards an outlet. Where falls are inadequate, or an outlet is undersized or blocked, water stands on the surface and works on every joint and detail continuously.

Correcting falls — by re-decking, adding firrings or using tapered insulation — adds cost to a replacement, but it addresses the reason the previous covering failed. Where we think poor drainage caused the failure, we will tell you, because re-covering without fixing it repeats the outcome.

Getting a realistic flat roof price

Send us a description and a few photographs, including the inside where there is damage, and we can usually tell you which range of work you are likely in: a contained repair, a re-cover, or a strip and replace. A firm price follows an inspection of the roof and its details.

Related pages: flat roofing, felt roofing, GRP fibreglass roofing, EPDM roofing and liquid roofing.