What lead flashing is and why it matters

Lead flashing is the shaped metal you see stepped into brickwork or dressed over tiles and slates. Its job is simple but crucial – seal the junctions where different building materials meet so wind driven rain cannot track behind the roof covering. Typical junctions include chimneys, abutments where roofs meet walls, roof windows, flat roof edges, parapets, and any penetrations such as flues.

Lead remains the most reliable solution for these junctions because it is strong, malleable, and handles expansion and contraction without tearing when installed correctly. With the right specification, lead flashings routinely last decades, which makes them a cost effective way to keep your home dry through the changeable Milton Keynes weather.

Where flashing is used on your roof

• Chimneys – apron (front), step flashings to the sides, and a back gutter with saddle at the rear
• Abutments – where a sloping roof meets a wall, typically with individual soakers and stepped flashings
• Valleys and intersections – areas that concentrate water and need careful weathering
• Roof windows and skylights – perimeter flashing kits to keep edges watertight
• Flat roof upstands and parapets – cover flashings and cappings to protect membranes and brickwork
• Pipes and flues – collars and weathering pieces around penetrations

Each of these details has specific rules for sizing, laps, fixings, and joint spacing. Get those right and the risk of leaks drops sharply. Get them wrong and even a new roof can let water in within months.

How lead flashing stops water getting in

Rainwater seeks out gaps, especially in strong winds. Proper flashing works as a system to shed water safely back onto the weather surface:

• It bridges between dissimilar materials – for example slate or tile to brick or GRP to masonry
• It forms drips and laps that send water down the roof face instead of behind it
• It uses upstands that are high enough to resist splashback in heavy weather
• It allows for thermal movement – correct lead code and joint spacing prevent fatigue
• It integrates with related parts – soakers, back gutters, saddles, wedges in chases, and compatible sealants

Think of flashing as a chain. If one link is weak – perhaps a short lap or a missing soaker – the whole detail is at risk during the next storm.

Common flashing failures and causes

• Split or fatigued lead – often caused by over long lengths with no expansion breaks or using too light a code where Code 4 or Code 5 is needed
• Short laps – capillary action and wind driven rain can force water behind the flashing
• Loose chases – failed mortar or sealant means the flashing is no longer secured into the brickwork
• Missing soakers at abutments – water can track under the tiles and into the wall
• No saddle or shallow back gutter behind chimneys – water pools, overflows and finds a way in
• Incompatible fixings – dissimilar metal contact can accelerate corrosion
• Debris build up – leaves and mortar behind chimneys cause water to back up under flashings
• Flat roof tie in issues – low upstands or unsupported lead at membrane edges

Early warning signs to look for

• Brown water stains on chimney breasts or ceilings near walls and valleys
• Drips during strong winds but not during light vertical rain
• White carbonate staining on brickwork below the flashing line
• Visible splits, lifted edges, or patch repairs with mastic
• Green streaks or moss trails below junctions
• Daylight visible around a chimney or abutment when you are in the loft

These symptoms point to junction issues, but a professional inspection confirms the root cause and the best way to fix it for the long term.

Safe homeowner checks vs professional inspection

Your safety comes first. Please avoid climbing on the roof. From ground level or with binoculars you can:

• Look for splits or lifting in the flashing and missing mortar where it enters brickwork
• Check for staining on ceilings or the face of chimney breasts
• Look in the loft for dark patches, damp insulation, or drips near the chimney or abutment

Our professional inspection typically includes:

• Close range checks of lead code, length, laps, and fixings
• Assessment of soakers, saddles, and back gutters around chimneys
• Upstand height and water path checks for local exposure levels
• Photos and short video so you can see exactly what we see
• A clear written plan with choices – targeted repair, partial renewal, or full replacement

Repairs vs replacement – options and materials

Targeted repairs

• Secure loose flashings into chases with lead wedges and repoint with suitable mortar or sealant
• Extend short laps and create proper drips to shed water
• Add missing soakers along abutments under each course
• Clear debris and form or deepen back gutters behind chimneys

Like for like replacement

• Full chimney set – new Code 5 apron and back gutter with saddle, Code 4 step flashings, and correctly sized soakers
• Abutment renewal – new stepped flashing, soakers, and correctly chased and wedged detail
• Skylight perimeter – matched cover flashings that integrate with the roof covering

Specifications we work to

• BS EN 12588 milled lead sheet – typically Code 4 for soakers and steps, Code 5 for aprons and back gutters depending on span and exposure
• Maximum single lengths to control movement, with laps and expansion joints as required
• Lead compatible fixings and clips and patination oil to control staining
• High quality masonry sealants or mortars suitable for MK brickwork and weather conditions
• Considered alternatives such as GRP or formed aluminium if requested or where weight or heritage restrictions apply

Our aim is simple – finish once, finish right, and leave you with a junction that performs for decades, not seasons.

UK standards and Building Regulations in practice

• Lead sheet – BS EN 12588 compliance, correct code selection, and joint spacing to manage thermal movement
• Detailing – Lead Sheet Training Academy guidance for laps, steps, aprons, back gutters, and saddles
• Moisture – Approved Document C requires junctions to resist water penetration and damp
• Structure – Document A checks if heavier materials or structure changes are proposed. Flashing work alone rarely changes loading
• Fire – Document B clearances around flues and use of suitable non combustible materials
• Ventilation – Document F ensures abutment detailing does not block airflow through the roof
• Energy – Document L considerations if more than 25 percent of a roof is refurbished, where insulation upgrades may be triggered
• Notifications – Like for like flashing repairs or replacement are usually non notifiable. If more than 25 percent of the roof is refurbished or structural elements are changed, Building Control needs to be informed. We advise case by case

You get clear guidance at quote stage so you know exactly what applies to your project and why we recommend a given detail.

Our step-by-step repair process

1. Assessment – we inspect, photograph, and confirm the fault and any related issues such as missing soakers or blocked back gutters
2. Specification – we set the correct code, length, laps, and fixings, and decide whether a repair or renewal is the right choice
3. Preparation – safe access, chase cutting where required, brick cleaning, and substrate checks
4. Installation – lead shaped and dressed, soakers set, laps formed, wedges fixed, and joints finished
5. Finishing – patination oil where appropriate and neat repoint of chases
6. Proof – photos and a walk through so you can see what was done and why
7. Aftercare – written workmanship guarantee and care advice

Case study – chimney leak in Bletchley

A 1930s semi in Bletchley had damp marks down the chimney breast after every storm. The roof was fairly new but the chimney junction kept leaking.

Findings: the front apron was Code 3 and too light, side flashings had short laps, there was no rear saddle, and the mortar pointing in the chases had failed. Water pooled behind the stack then tracked under tiles and into the loft.

Fix: we installed a Code 5 apron and a deepened back gutter with a formed saddle, fitted Code 4 stepped flashings with new soakers to every course, cut and wedged into the chases, repointed with suitable mortar, and applied patination oil. We cleared debris and improved the water path behind the stack.

Result: no further ingress through multiple storms. The customer later booked gutter servicing and left another five star review.

Typical costs and what affects price

Every roof is different, so we provide a free assessment and a clear, written quote. Typical guide ranges are below to help set expectations:

• Repointing and securing existing flashing – from £120 to £280 per junction
• Chimney apron or step flashing replacement – from £250 to £450 per element
• Complete chimney flashing set including soakers and back gutter with saddle – typically £650 to £1,100 depending on size and access
• Abutment renewal per linear metre including soakers – from £140 to £220
• Skylight perimeter reflash – from £280 to £650 based on roof type and brand

Final price depends on access needs such as scaffold or tower, roof pitch and height, chimney size, and the condition of surrounding tiles or slates. We always share photos and explain options, and we do not upsell work you do not need.

Why Milton Keynes homeowners choose Maxwells

• Local knowledge – daily work across MK estates and nearby towns means we know local building styles and exposure
• Owner led standards – Luke Maxwell oversees quality and specification on every project
• Trusted reputation – 80+ five star Checkatrade reviews and a 5 star Google rating
• Fast response – same day or next day callouts where possible for active leaks
• Right first time – British Standards materials and proven detailing for long lasting results
• Clear pricing – itemised quotes with photos and no hidden extras
• Full service – flashing, chimney repairs, roof repairs, re-roofing, gutters, skylights, and inspections

From a small flashing fix to full chimney reweathering, we deliver neat, durable work that protects your home for the long term.

Lead flashing FAQs

How long should lead flashing last?

With the correct code, laps, and expansion control, 50 years or more is common. Many traditional details last far longer when maintained.

Is mastic a good fix for flashing leaks?

Mastic is usually a short term patch. It breaks down under UV and movement. A proper repair corrects laps, soakers, and fixings so the joint is watertight without relying on sealant.

Do you guarantee your flashing work?

Yes. All flashing repairs and replacements come with a written workmanship guarantee. The length and terms are confirmed on your quote.

Will you need scaffolding?

It depends on height and access. Some details are safe from a tower or platform. For taller or complex work, scaffold is the safest and most efficient option. We specify the most cost effective safe method for your property.

Is flashing replacement notifiable to Building Control?

Like for like flashing repairs and replacement normally are not notifiable. If more than 25 percent of the roof is refurbished or the structure is altered, Building Control involvement is required. We advise on this as part of our service.

Areas we cover

We serve all of Milton Keynes and the surrounding area, including Stony Stratford, Newport Pagnell, Bletchley, Great Linford, Bradwell, Wolverton, Shenley Brook End, plus nearby towns such as Bedford, Northampton, and Luton. If you are close to MK, we will do our best to help.

Book your free flashing inspection

If you suspect your flashing is failing, we will inspect, photograph any issues, and explain the best options in plain English with a fixed quote.

• Phone: 07311091804
• Email: sales@miltonkeynesroofing.uk
• Website: miltonkeynesroofing.uk