How To Repair Roof Flashing?
Roof flashing is one of the most critical components of any roofing system, yet it’s often the first thing to fail. These thin strips of metal or lead are installed around chimneys, skylights, vents, and roof joints to channel water away from vulnerable areas. When flashing deteriorates, even a tiny gap can allow water into your home, leading to damp ceilings, damaged plasterwork, and costly structural repairs. The good news is that many flashing problems can be fixed without a full roof replacement.
At Severnside Roofing, we’ve helped countless homeowners across Shrewsbury and Shropshire tackle flashing issues before they turn into major leaks. Here’s our step-by-step guide to repairing roof flashing.
What Causes Roof Flashing to Fail?
Flashing can fail for a number of reasons. Age and weathering are the most common — over time, sealant dries out and cracks, metal corrodes, and the mortar holding flashing in place around chimneys crumbles away. The wet conditions typical of the Shropshire and Severn valley area can accelerate this process significantly. Thermal expansion and contraction through seasonal temperature changes can also cause flashing to lift or pull away from the roof surface, creating gaps that allow water in.
Tools & Materials You’ll Need
Before you begin, make sure you have the following to hand: a wire brush, roofing sealant or flashing cement, a caulking gun, a trowel, replacement flashing material (lead or aluminium), roofing nails, a hammer, and a secure, stable ladder. Always work in dry, calm conditions and follow safe working at height practices throughout.
Step 1: Inspect & Identify the Problem
Start with a careful inspection of the flashing and surrounding roof area. Look for sections that are lifted, buckled, cracked, or missing entirely. Check for rust staining on the metal and damp patches on your ceilings below. Pinpointing exactly where and how the flashing has failed will help you decide on the right course of action before you start any repair work.
Step 2: Clean the Area Thoroughly
Use a wire brush to remove all traces of rust, old sealant, dirt, and debris from the damaged flashing and the surfaces around it. Any new sealant or patching material will only bond effectively to a clean, dry surface, so this step is worth taking your time over. Wipe the area down with a dry cloth before proceeding.
Step 3: Re-seal Small Cracks & Gaps
For minor cracks or slightly lifted edges, a quality roofing sealant or flashing cement is often all that’s needed. Apply it generously along the joint, press the flashing firmly back into position, and smooth it off with a trowel. Check carefully for any remaining gaps and seal them fully. This method is ideal for chimney and skylight flashing that has simply dried out or shrunk over time.
Step 4: Patch Damaged Sections
Where a section of flashing is badly corroded or torn, cut a patch from matching flashing material. Lead is the traditional and most durable option, particularly on older Shropshire properties, while aluminium is a lighter and more affordable alternative. The patch should overlap the damaged area by at least 6cm on each side. Apply flashing cement to the underside, press the patch firmly into place, and seal all edges to prevent any water from getting underneath.
Step 5: Replace Flashing Completely (If Needed)
When damage is too extensive to patch, full replacement is the best solution. Carefully remove the old flashing using a pry bar or trowel, being mindful not to disturb surrounding tiles. Fit the new flashing to match the original profile, secure it with roofing nails, and seal all joints and edges thoroughly with flashing cement. If the flashing runs around a chimney stack, re-point any disturbed mortar once the new flashing is bedded in place.
When to Call a Professional Roofer
Minor flashing repairs are manageable for a confident DIYer, but more extensive work — especially on older properties, steep roofs, or complex chimney stacks — is best handled by a qualified professional. Working at height always carries risk, and an incorrectly fitted repair can make water ingress worse rather than better.
If you’re unsure about any aspect of the repair, the team at Severnside Roofing is always happy to help. We provide expert flashing repairs across Shrewsbury and the wider Shropshire area. Get in touch today for a free, no-obligation quote and let us ensure your roof is fully protected.
