A Guide to Roof Flashing and Why It Fails (Milton Keynes)

If you have spotted damp patches, ceiling stains, or drips that show up during heavy rain, the culprit is often not the tiles – it is the flashing. Across Milton Keynes, Newport Pagnell, Bletchley, Stony Stratford and nearby towns, a large percentage of roof leaks trace back to tired, cracked, slipped or poorly fitted flashing around chimneys, valleys, abutments and skylights.

Maxwells Roofing is a family-owned, owner-led local company in Milton Keynes. We have 80+ 5* reviews on Checkatrade and 5* reviews on Google. Our team repairs, replaces and maintains flashing on pitched and flat roofs, helping homeowners keep their properties watertight all year.

Call 07311091804 for a free inspection and fixed quote or email sales@miltonkeynesroofing.uk. Same-day or next-day attendance is often available for urgent leaks.

What is roof flashing?

Flashing is the protective material used wherever your roof covering meets an upstand, junction or penetration – the most leak-prone parts of any roof. Its job is simple but critical: create a durable, weatherproof barrier that diverts water away from joints and safely into gutters and downpipes.

Common places you will find flashing include:

• Around chimneys – apron flashing at the front, step flashing into the side brickwork, and a formed back gutter to handle run-off
• Along roof valleys where two slopes meet
• Around skylights, Velux roof windows and roof lanterns
• At abutments where a roof meets a wall, dormer, or parapet
• At the edges and upstands of flat roofs
• Around soil stacks, flues and ventilation penetrations
• In box gutters and at parapet walls

When flashing is specified and fitted correctly, it is a quiet hero. When it is undersized, cracked, loose or poorly detailed, it lets water creep behind the roof covering and into your property. That is why careful installation and timely maintenance matter.

Flashing types you will see in Milton Keynes

Different roof details, styles and budgets call for different materials. The most common choices around Milton Keynes include:

• Lead flashing: Traditional, long-lasting and very formable. Correct code selection, lap lengths, fixings and allowance for thermal movement are essential for durability and compliance.
• Lead-free alternatives: Modern polymer or bituminous composites that are lightweight, easy to shape and theft-resistant. Ideal where weight, cost or appearance dictate an alternative to lead.
• Aluminium and steel flashings: Used on many modern builds where pre-formed profiles are needed for cappings, trims and cladding interfaces.
• GRP trims: Common on fibreglass flat roofing systems and parapet details to create neat, drip-safe edges.
• EPDM-compatible flashings and termination bars: Used on rubber roofs where the membrane meets walls or penetrations.
• Pre-formed skylight flashings: Manufacturer kits for roof windows such as Velux, designed to match tile or slate profiles and preserve warranty coverage.

Choosing the right material is only half the job. Getting the detailing right – chase depths, laps, clips, soakers, underlay reinstatement and pointing – is what keeps water out for decades rather than years.

The top reasons roof flashing fails

Understanding why flashing fails helps us put in place a fix that lasts – not just a quick sealant patch.

• Age and weathering: UV, heat and freeze-thaw cycles cause cracks, splits and fatigue over time, especially in older mortars and sealants.
• Poor installation: Wrong code of lead, short laps, over-reliance on sealant instead of mechanical detailing, or inadequate fixings.
• Thermal movement: Metal expands and contracts. If allowance is not made, flashing can fatigue, split or pull out of chases.
• Mortar failure: Cracked, missing or weak mortar around chimney flashings lets water track behind the lead or alternative material.
• Storm and wind uplift: High winds can lift loose or poorly fixed flashings and expose vulnerable joints.
• Blocked gutters and valleys: Standing water backs up and creeps under flashings that were never intended to be submerged.
• Foot traffic and trades damage: Walking on fragile details or resting ladders against flashings causes micro-cracks that worsen over time.
• Building movement: Settlement or structural movement can open gaps around abutments and parapets.
• Galvanic corrosion: Incompatible metals in contact can corrode and fail prematurely.

Leak now? Call 07311091804 and our local team will book a prompt visit.

Early warning signs to look for

Spotting issues early is the cheapest way to protect your home.

Outside signs:

• Flashing that is lifting, dislodged or visibly split
• Staining, efflorescence or green growth on brickwork below an abutment
• Cracked or missing mortar around chimney flashings
• Debris build-up or standing water in valleys
• Rust staining on metal flashings

Inside signs:

• Brown or yellow water marks on ceilings or walls near chimneys or roof edges
• Damp insulation or musty odours in the loft
• Light visible through junctions when you check the loft in daylight

Safety first: Do not walk on fragile roofs, steep pitches or wet surfaces. Ground-level checks with binoculars or a professional inspection are safer.

DIY vs professional repair – what is safe?

Some simple checks are fine for a confident homeowner. Others are best left to trained roofers with the right access equipment and experience.

Reasonable DIY steps:

• Visual checks from the ground or a stable ladder when safe to do so
• Clearing low gutters and downpipes to keep water moving
• Temporary re-sealing of a small, accessible surface crack on a non-fragile area

Call a professional for:

• Chimney apron, step flashing and back gutters
• Valley linings and parapet details
• Cutting chases into masonry and correct repointing
• Any work on membranes such as EPDM, GRP or felt
• Skylight and roof window flashings to preserve manufacturer warranties
• Working at height on steep or fragile roofs

Why take care? Flashing is a system detail. A quick sealant patch can hide a deeper issue and allow hidden water ingress that leads to timber rot, insulation damage and mould.

How we repair or replace failed flashing

Every roof is different. Our owner-led team assesses the detail, identifies the root cause and then specifies a durable, compliant fix that suits your roof style and budget.

Typical repair and replacement approaches:

• Chimney step and apron flashing (lead or lead-free): Remove failed pointing, cut chases to the correct depth, install new step and apron flashing with proper laps, clips and fixings, then repoint with the correct mortar or approved lead sealant. Form a suitable back gutter to carry water and shed debris.
• Valley flashing: Replace corroded or undersized valley linings with correctly specified lead, GRP or other approved systems. Reinstate valley boards and support, set the correct falls, and ensure outlets are clear.
• Abutment and side flashing: Install stepped or soaker flashings in line with industry best practice, making sure slates or tiles interface correctly and underlays are reinstated for a continuous barrier.
• Skylight and roof windows: Fit the manufacturer’s flashing kit matched to your specific tile, slate or standing seam profile. Reinstate underlay and weatherproofing to maintain a warranty-safe installation.
• Flat roof upstands and trims: Reinstate compatible trims and termination bars, redress membranes, and seal with approved components for EPDM, GRP or felt systems.
• Mortar and pointing: Remove failed mortar cleanly and repoint with suitable mixes, or use specialist sealants where appropriate for movement and weathering.

What about cost and timelines? After a free inspection, you will receive a clear, written quote with the scope of works, materials, warranty terms and the expected timeline. On urgent leaks, we will do our best to prioritise a same-day or next-day appointment.

Need help now? Call 07311091804 and we will book you in.

Preventative maintenance that saves money

A little routine care goes a long way. Simple steps reduce the risk of flashing-related leaks and expensive callouts.

• Book a professional roof check every 12 to 24 months, ideally before winter
• Inspect after storms for lifted flashings, dislodged tiles and debris in valleys
• Keep gutters and valleys clear so water does not back up under flashings
• Repoint chimney brickwork early if mortar is cracked or crumbling
• Avoid unnecessary foot traffic on fragile areas and use proper access equipment

We offer routine inspection visits across Milton Keynes, Northampton, Bedford, Luton and all surrounding villages to keep small issues from becoming big ones.

UK Building Regulations you should know

Small like-for-like flashing repairs usually do not require Local Authority Building Control. Larger refurbishments or partial re-roofs can trigger requirements. Here are key points to be aware of:

• Part C – Resistance to moisture: Flashing and junction details must keep out rain and manage condensation. Correct laps, upstands and compatible materials matter.
• Part B – Fire safety: Flat roofing systems must meet fire performance requirements such as BROOF(t4). Replacing coverings near boundaries needs attention to compliance.
• Part A – Structure: Significant changes or heavier coverings may require a check that the structure can support the load.
• Part F – Ventilation: Re-roofing is a sensible time to ensure loft ventilation meets current guidance to prevent damp and mould.
• Part L – Conservation of fuel and power: If replacing more than 25 percent of the roof covering, upgraded insulation is usually required.

Notification rules: Where more than 25 percent of the roof is refurbished or there are structural changes, you must notify Local Authority Building Control or use an approved Competent Person Scheme. We will advise you case by case and coordinate the correct process when required.

Our promise: We follow manufacturer instructions and UK best practice, specify reputable materials and detail every job properly so you get a durable, compliant result.

Local case studies

Newport Pagnell – chimney leak stopped at source
A homeowner noticed ceiling stains after persistent rain. We found cracked mortar, undersized step flashing and a shallow back gutter. We re-chased the brickwork, installed correctly coded lead step and apron flashings with proper laps, formed a new back gutter and repointed. The home stayed dry through winter storms.

Bletchley – valley lining replacement
A tiled valley had a corroded lining and poor fall, causing overflow in downpours. We replaced the lining with a durable GRP system, adjusted support boards for proper fall, refixed the cut tiles and cleared outlets. Result: better flow and no further ingress.

Why choose Maxwells Roofing

• Family-owned and local: We are Milton Keynes specialists who know local house types and weather patterns inside out.
• Owner-led quality: Company owner Luke Maxwell oversees workmanship and standards on every project.
• 5-star reputation: 80+ 5* reviews on Checkatrade and 5* reviews on Google.
• Fully insured and qualified: Safe working practices and compliant installations.
• Fast response: Same-day or next-day visits for urgent leaks where possible.
• Honest pricing: Clear, written quotes with no hidden extras.

Service areas: Milton Keynes, Northampton, Bedford, Luton, Stony Stratford, Newport Pagnell, Bletchley, Great Linford, Bradwell and all nearby villages.

Roof flashing FAQs

How long should lead flashing last?

When installed and detailed correctly, lead flashing can last for several decades. Most failures are caused by poor detailing, movement, or degraded pointing rather than the lead itself.

Can I just reseal a cracked flashing?

Sealant is a temporary measure at best. If the chase is shallow, laps are short or movement is not allowed for, a simple reseal will not last. We assess the whole detail so you get a durable, cost-effective repair.

My roof only leaks in wind-driven rain – why?

Wind can push water up and under loose or poorly lapped flashings. We check lap directions, fixings and exposure, then specify the right remedy to resist local wind conditions.

Do you repair lead theft damage?

Yes. We can replace like-for-like or fit modern, theft-resistant alternatives that deliver a traditional look with improved security.

Will I need Building Control for flashing work?

Not usually for small like-for-like repairs. Larger refurbishments such as replacing over 25 percent of the roof covering typically require notification. We will advise you and handle the process where needed.

Can you inspect with a drone?

Yes, where appropriate. Drone surveys help us assess tricky areas safely and quickly, subject to weather and permissions.

Get your free quote

Do not wait for the next storm to test your flashing. A quick inspection today can prevent costly repairs tomorrow.

Call Maxwells Roofing on 07311091804
Email: sales@miltonkeynesroofing.uk

Looking for related help? Explore our services including Roof Repairs, Roof Inspections, Chimney Repairs, Flat Roof Systems and Gutter Maintenance.