How to Fix Leaking Garage Roofs

• Cracked, rusted, or warped panels – Common in metal, cement fibre, and asbestos roofs.
• Brittle or torn roofing felt – A common issue with flat roofs.
• Loose, missing, or shifting roof sheets – Panels that have moved due to wind exposure or poor installation.
• Dark patches or mould growth on the ceiling – Indicating moisture ingress over time.

• Once water infiltrates cracks, rust spots, or porous areas, it can spread quickly, weakening the entire structure.
• In winter, freeze-thaw cycles worsen existing cracks as trapped moisture expands.
• Asbestos roofing, common in older UK garages, becomes particularly hazardous when damaged, as it can release harmful fibres into the air.

If your garage roof is over 15-20 years old or has widespread damage, replacing it with a modern, waterproof alternative is the safest and most cost-effective solution. Options like galvanised steel, EPDM rubber, or GRP fibreglass provide long-lasting protection.

• Blocked or clogged gutters – Leaves, dirt, and debris prevent water from draining away.
• Leaking or misaligned downpipes – Causing water to spill onto garage walls or foundation.
• Poor roof pitch – Flat or low-sloped roofs are particularly vulnerable to standing water.
• Lack of adequate drainage channels – Water accumulates near the base of the garage, increasing damp issues.

• Standing water on a flat roof accelerates roofing material deterioration.
• Overflowing gutters can cause damp and rot in wooden garage structures.
• Water pooling at the base of the garage can lead to foundation damage over time.

• Regularly clean gutters to remove blockages.
• Ensure downpipes are directing water away from the garage.
• If your garage has a flat roof, consider a pitched roof replacement to improve drainage.

• A poorly ventilated garage traps warm, moist air inside.
• When this air meets the cold surface of the garage roof, it condenses into water droplets.
• Over time, these droplets accumulate and drip down, causing what appears to be a ‘leak.’

• Water dripping from the ceiling, but no visible cracks or holes in the roof.
• Damp or mould forming along the walls, ceiling, or inside stored items.
• The issue is worse in cold weather but disappears when the temperature rises.

• Mould growth can lead to structural decay and respiratory issues.
• Condensation can cause tools, bikes, and stored goods to rust.
• Wooden garage frames or interior shelving can rot over time.

• Improve garage ventilation by installing air bricks or vents.
• Upgrade to an anti-condensation garage roof replacement, such as galvanised steel sheets with a built-in vapour barrier.

• Improper sealing of overlapping roof sheets – Leading to gaps that allow water to seep through.
• Poor flashing or sealant application – Causing leaks where the roof meets walls or edges.
• Insufficient pitch – If a roof is too flat, water won’t drain properly, leading to pooling and damage.

• Poorly installed roofs will continue to leak, no matter how many temporary repairs are applied.
• If materials weren’t properly secured, wind uplift can loosen panels or displace roof sections.
• Short-term fixes won’t last – a low-quality roof will require constant maintenance and repairs.

If you suspect poor workmanship, a full garage roof replacement with professional installation is the best course of action. Choosing high-quality materials like EPDM rubber, GRP fibreglass, or galvanised steel ensures maximum durability and waterproofing.

Start by checking the inside of your garage for signs of water ingress. Look for:

• Damp patches, mould growth, or dark water stains on the ceiling or walls.
• Water pooling on the floor, which may indicate a leak from above or water tracking down from another surface.
• Drips or active water ingress during rainfall—this is the best time to observe where water is entering.

If the leak is difficult to pinpoint, use a torch to scan for cracks, small holes, or damp streaks on the underside of the roof panels.

A visual inspection of the outside of your garage roof will help confirm the source of the leak. Check for:

• Cracked, corroded, or missing panels that could be allowing water through.
• Gaps in flashing where the roof meets the garage walls, as this is a common weak point.
• Pooling water or signs of previous water retention, particularly on flat roofs.
• Blocked gutters or downpipes causing water to overflow onto the roof surface or garage walls.

For flat garage roofs, look closely at any seams or joins, as these are often the first areas to degrade.

If the leak is hard to locate, a controlled water test can help. On a dry day, run a hose over different sections of the roof, starting at the lowest point and working upward. Have someone inside the garage to observe where water first appears. This method is particularly useful for identifying small cracks or gaps that might not be obvious.

For small holes or cracks, apply a waterproof silicone sealant or roof repair mastic. These flexible sealants can temporarily block water ingress and are ideal for minor leaks in felt, metal, or cement fibre roofing. However, they are not a permanent fix, as exposure to weather will cause them to break down over time.

For flat garage roofs, a liquid waterproof membrane can provide a temporary seal against moisture. These coatings are easy to apply and can extend the lifespan of a deteriorating roof, but they won’t fix structural issues. If your garage roof is already showing widespread signs of wear, a replacement will be necessary in the near future.

Self-adhesive roofing tape can be used to patch small leaks in metal, felt, or rubber garage roofs. This solution is quick and easy but only provides short-term waterproofing. Eventually, the adhesive will degrade, and the underlying problem will need a more permanent solution.

Poor drainage can make a leaking garage roof worse. Clear out clogged gutters and downpipes to prevent water from pooling. If water is collecting on a flat roof, consider installing additional drainage outlets or upgrading to a pitched roof to reduce standing water issues.

A brand-new garage roof provides a 100% watertight solution, eliminating leaks for years to come. Unlike patchwork repairs that degrade over time, a replacement ensures full protection against rain, damp, and condensation.

Ongoing repairs can quickly add up. Instead of repeatedly paying for sealants, coatings, and temporary fixes, investing in a new garage roof eliminates constant maintenance costs and saves you money in the long run.

Older garage roofs were often built with materials that degrade over time. A replacement allows you to upgrade to high-quality, weather-resistant options such as:

• EPDM rubber roofing – Highly durable, flexible, and waterproof.
• GRP fibreglass roofing – Strong, lightweight, and maintenance-free.
• Steel roofing panels – Galvanised for superior protection against rust and corrosion.

These materials are specifically designed to withstand the British climate, ensuring long-lasting durability.

Modern garage roofing systems include built-in anti-condensation layers, preventing moisture buildup and protecting your garage from damp. This is especially beneficial for garages that store valuable items, tools, or vehicles.

Many UK garages still have old asbestos roofing, which not only leaks but poses a serious health risk. Asbestos deteriorates over time, releasing harmful fibres into the air. If your garage has an asbestos roof, replacing it with a safe, modern alternative is essential. At Excel Roofing, we are HSE-registered for safe asbestos removal, ensuring the process is handled professionally and in full compliance with regulations.