Flat roofs are one of the most common roofing systems on commercial and residential properties across Ireland — and one of the most misunderstood. The wrong material choice, a poorly planned repair, or simple neglect can turn a straightforward job into an expensive headache. These practical tips will help you make smarter decisions, avoid the most common pitfalls, and get the longest possible life from your flat roof.
Choose the Right Waterproofing System
Not all flat roof coatings are equal. The material you choose has a direct impact on how long your roof lasts, how well it performs, and how much you spend over its lifetime.
Traditional felt and bitumen systems are still widely used, but they have significant limitations. Felt joints are vulnerable to splitting, especially during Ireland’s freeze-thaw cycles. Bitumen degrades under UV exposure and becomes brittle over time.
Modern liquid-applied systems offer a superior alternative:
- LAVA 20 — A high-performance liquid waterproofing membrane that bonds directly to the existing surface, creating a seamless barrier with no joints or seams to fail
- Polyurea coatings — Rapid-curing, extremely durable coatings that can withstand foot traffic, chemical exposure, and extreme temperature swings
- Fibreglass (GRP) — Rigid and long-lasting, but requires skilled installation and cannot flex with structural movement
The best system depends on your roof’s size, condition, and how it is used. A free professional survey will identify the right solution for your specific situation.
Inspect Your Roof Regularly
Most flat roof problems are preventable — if you catch them early. A simple visual inspection twice a year (spring and autumn) can save you thousands in emergency repairs.
Here is what to look for:
- Standing water — Flat roofs should have a slight fall to drainage points. Persistent ponding suggests blocked outlets or sagging decking
- Blistering or bubbling — Air trapped beneath the membrane indicates adhesion failure
- Cracking at edges and upstands — The most vulnerable areas on any flat roof, especially where the surface meets parapet walls
- Vegetation growth — Moss and weeds hold moisture against the surface and accelerate deterioration
- Blocked gutters and outlets — The single most common cause of flat roof leaks in Ireland
You do not need to climb onto the roof yourself. A pair of binoculars from ground level, or photos from an upstairs window, can reveal most issues. For a thorough assessment, our team provides free roof inspections with no obligation.
Do Not Patch Over Existing Problems
This is one of the most expensive mistakes property owners make. When a flat roof leaks, the instinct is to apply a quick patch over the visible damage and move on. The problem is that water rarely enters directly above where the stain appears on the ceiling.
Water travels horizontally along the roof deck, insulation layers, and timber joists before it finds a path downward. A patch over point A may do nothing for the actual entry point at point B — and meanwhile, the hidden damage continues to spread.
Before any repair, the source of the leak must be properly identified. This often requires a systematic inspection of the entire roof surface, flashings, valley gutters, and drainage points. Only then can the right repair be specified.
A proper diagnosis before repair saves more money than any quick fix. The cheapest repair is the one that works first time — and that starts with understanding exactly where and why the roof is failing.
Prioritise Drainage
Poor drainage is the root cause of most flat roof failures in Ireland. Our climate delivers sustained rainfall — not the brief downpours that flat roofs in drier climates are designed for. If water cannot leave the roof surface quickly, it will find its way through.
Key drainage principles:
- Clear outlets and hoppers every season — leaves, moss, and debris accumulate faster than most people expect
- Check internal downpipes for blockages, especially at bends and junctions
- Ensure adequate falls — a minimum 1:80 fall to drainage points is recommended for flat roofs
- Consider overflow outlets — secondary drainage prevents catastrophic ponding if primary outlets block
If your flat roof has persistent ponding issues, it may need re-grading with a tapered insulation system before any new waterproofing is applied. This is standard practice for professional flat roof waterproofing projects.
Hire the Right Contractor
The quality of the installation matters as much as the materials used. A premium waterproofing system applied incorrectly will fail just as quickly as a cheap one.
When choosing a flat roofing contractor in Ireland, look for:
- Proven experience with your specific roof type — commercial, domestic, metal roofs, or asbestos roofs each require different expertise
- Material manufacturer approval — reputable contractors are trained and certified by the manufacturers whose products they install
- Written warranty — both on materials and workmanship, ideally backed by the manufacturer
- Public liability and employer’s liability insurance — non-negotiable for any contractor working at height
- HSA compliance — Health and Safety Authority requirements for working at height in Ireland
Avoid contractors who quote without inspecting the roof in person. A reliable firm will always conduct a site survey before providing a fixed price.
Plan for the Long Term
The cheapest option upfront is rarely the cheapest option over 10 or 20 years. A budget felt repair might last 3–5 years. A professional liquid-applied waterproofing system can last 20–25 years with minimal maintenance.
When evaluating quotes, consider the total cost of ownership:
- Initial cost — materials, labour, access equipment
- Expected lifespan — how many years before the next major intervention
- Maintenance requirements — some systems need periodic recoating, others do not
- Warranty coverage — what is actually covered, and for how long
- Energy performance — a well-insulated, sealed roof reduces heating costs year after year
A LAVA 20 waterproofing system with a 20-year warranty, for example, costs significantly less per year of service than a felt repair that needs replacing every 5 years.
Do Not Ignore Small Leaks
A small leak is not a small problem — it is a large problem in its early stages. Every flat roof leak in Ireland follows the same pattern if left untreated: minor staining becomes active dripping, which becomes saturated insulation, which becomes structural timber damage.
The earlier you act, the simpler and cheaper the fix. If you have noticed any signs of water ingress — staining, damp smell, peeling paint, or cold spots on ceilings — do not wait for it to get worse. Our guide to the top reasons not to delay roof repairs explains exactly why early action saves money.
Get Expert Advice on Your Flat Roof
Not sure what your flat roof needs? We provide free, no-obligation roof surveys across Dublin and Ireland. Our team will inspect your roof, identify any issues, and recommend the most cost-effective solution — from a targeted repair to a full flat roof waterproofing system.
Make the smart decision — get a professional opinion before you spend.
