If you have a leak around a chimney, valley or flat roof section in Bury St Edmunds, failed or poorly installed lead work is one of the most likely causes.
Call any time. Calls are answered day and night and passed straight to our roofers.
Lead is used in roofing wherever two surfaces meet or where water needs to be directed away from a joint. Chimney flashings, step flashings up a party wall, valley gutters, abutments where a roof meets a vertical face, and flat roof upstands all rely on lead to stay watertight. When lead is dressed correctly and fixed to the right Code, it lasts for decades. When it is cut short, bonded badly or left unsecured, it fails within a few years and lets water into the roof structure or down internal walls.
Lead comes in numbered Codes that refer to its thickness. Code 3 (1.32 mm) is the lightest and is suitable only for soakers. Code 4 (1.80 mm) is used for most chimney flashings and step flashings. Code 5 (2.24 mm) is the standard for valley gutters, parapet gutters and flat roof work. Code 6 (2.65 mm) is used where extra weight and rigidity are needed, for example on wide valleys or exposed upstands. Using the wrong Code is one of the most common shortcuts taken by inexperienced roofers, and it shortens the life of the lead significantly.
Understanding what a proper lead work job involves helps you ask the right questions and recognise whether the work being offered is up to scratch. Below is how a lead flashing or valley job should unfold, from the moment someone looks at the roof to the moment the van drives away.
Before any lead is cut or dressed, the area needs a proper look. For chimney flashings, that means getting onto the roof, not just viewing from the ground. A roofer needs to see whether the existing lead is cracked, lifting, poorly bonded, or simply missing sections. They also need to check the masonry around the chimney: if the pointing is shot or the stack is leaning, that needs addressing before new lead is fitted, otherwise the new work is compromised from day one.
For valleys, the inspection should check the underlying timber structure. A sagging or rotten valley board will cause new lead to ripple and pool water in the wrong places. For flat roof upstands and abutment flashings, the roofer needs to check whether the existing lead has been chased into the masonry or just stuck with mastic (a common bodge). Mastic shrinks and cracks. A proper chase and pointing job is the only reliable method.
A good roofer will tell you exactly what they find and explain what needs to come out and why. If someone quotes for new flashings without getting on the roof first, that is a warning sign.
Old lead is removed carefully. On a chimney, the existing flashing is lifted out of the mortar chase, and any old mortar or sealant is raked back. The chase itself is inspected: sometimes it is too shallow, which is why the previous lead failed. A chase needs to be at least 25 mm deep to grip the lead properly once it is re-pointed.
Old soakers are removed from under the tiles or slates where they exist. On a valley, the old valley lead is taken out and the valley board underneath is inspected. If the board is soft, spongy or showing rot, it is replaced at this stage rather than left to cause problems later.
Old lead is a material with scrap value, so reputable roofers will remove it and account for it properly. If a quote assumes you supply or remove old lead yourself, that is worth querying.
This is the step that most homeowners never see but that makes the biggest difference to how long the work lasts. On a chimney, the masonry around the stack is inspected and re-pointed where needed before any lead is dressed. Cracked pointing allows water to bypass even perfect lead. The chase line is cut or deepened if necessary, and any loose material is cleared out.
On a valley, the board is checked for level and any fixings are tightened or replaced. Where the valley sits over rafters, any movement in the structure needs to be identified. Lead is a heavy material and it moves with temperature changes. If the substrate beneath it is not solid, the lead will work loose over time.
For abutment flashings where a lean-to or extension roof meets a house wall, the wall itself needs to be sound. Soft or spalling brickwork should be made good before the new lead goes in, otherwise the pointing that holds the lead in place will not last.
Lead is cut from a roll to the dimensions needed for the specific situation. For chimney back gutters, the lead needs to be large enough to carry water away from the back of the stack without pooling. For step flashings, each piece is cut individually and lapped correctly so water cannot track back behind the sheet. For valley gutters, the lead is lapped in lengths of no more than 1.5 metres to allow for thermal movement without buckling.
Dressing means shaping the lead by hand using a bossing mallet and dresser to form it around corners, into internal and external angles, and across uneven surfaces. This is the skilled part of the job. Poorly dressed lead has thin spots where it has been stretched too far, or it lifts at the edges because the internal angles have not been closed properly. Either fault means leaks.
Lead is a soft metal and it expands and contracts noticeably with temperature changes. Lengths over 1.5 metres will buckle if they are fixed too rigidly, which is why proper lead work uses separate lapped lengths rather than one continuous sheet across a long run. Clips are used to secure the lower edge of each length without preventing the movement the lead needs.
Once the lead is dressed into position, the top edge is tucked into the chase and secured with lead wedges. The chase is then pointed with mortar to lock the lead in place. Pointing should be done with a mortar that is not too hard: a very hard cement mix can crack away from the lead as the lead moves with temperature, which opens a gap and lets water in. A lime-based or softer sand and cement mix is generally more appropriate for this detail.
Lead clips or cleats are used on flat sections and valleys to hold the lower edge of each length in place without fixing it rigidly. Clips are turned up behind the lead so they are invisible from above. Each clip is nailed or screwed to the substrate and then the lead is dressed over it. This prevents the lead from sliding down over time, which is a common failure on steeper pitches.
Once the lead is in and the pointing is done, the completed joint should be checked to make sure water cannot track behind it at any point. On a chimney, water should flow off the back gutter, down the step flashings and out over the apron at the front. Any lap that allows water to sit against a joint is a problem. A torch test in dry weather, where a hose is run over the roof while someone checks inside, is the most reliable way to confirm a flashing is watertight.
Tiles or slates disturbed during the work are re-bedded or re-nailed as needed. Valley tiles are re-cut and re-laid to the correct margin over the new valley lead. Any debris - old mortar, lead off-cuts, broken tile fragments - is cleared from the roof and from gutters. Gutters blocked with debris from roofing work are a common complaint after lead jobs, and a tidy roofer will check them before leaving.
Cracking and splitting in older lead is often caused by lead rot, where the surface of the lead oxidises and the material becomes brittle. This typically affects lead that is more than 50 or 60 years old and has been sheltered from rainfall, which prevents the protective patina from forming. South-facing chimney stacks are particularly prone to this because the lead gets very hot in summer.
Lifting and slipping lead is usually a sign that clips were not used or that lengths were fixed too rigidly without allowing for thermal movement. A single long sheet of lead fixed at both ends will buckle and eventually crack in the middle. Correct installation uses separate lapped lengths, each free to move independently.
Sealant repairs that have failed are one of the most common situations a roofer is called to inspect. Applying silicone or mastic over failing lead is a temporary measure at best. Sealants become brittle with UV exposure and rarely last more than a few years. The underlying lead needs to be properly repaired or replaced, not covered over.
Poorly dressed internal angles are a frequent cause of leaks on chimney back gutters. If the lead has not been properly bossed into the corner where the back of the stack meets the roof slope, there is a gap that allows water in. This type of fault is not visible from ground level and is easily missed if the inspection is done from a ladder rather than from the roof itself.
Lead work is priced by the job rather than by a simple rate, because the time involved depends heavily on the complexity of the detail and the access required. A straightforward chimney flashing replacement on a standard pitched roof in Bury St Edmunds typically costs in the range of £300 to £600, depending on the size of the stack and how many courses of step flashing are needed. A valley reline on a detached house is often in the range of £400 to £800. Larger or more complex jobs, such as parapet gutters or flat roof upstands with multiple angles, can run to £1,000 or more.
The cost of lead itself has risen sharply in recent years and is a significant part of the total price. Code 5 lead sheet currently costs in the region of £30 to £40 per square metre, and a valley or chimney job uses more material than homeowners often expect. A quote that looks unusually cheap is worth scrutinising carefully: the most common way to cut costs on lead work is to use a lighter Code than the job requires, or to use short lengths that are not properly lapped.
Always ask what Code of lead will be used and where, and ask whether the quote includes re-pointing the chase and any necessary preparation of the substrate. These details separate a proper job from a quick fix.
On a tiled roof, lead is most commonly found at chimney flashings and open valleys. Chimney work involves a back gutter, two sets of step flashings and a front apron. All four pieces need to be in good order: it is not unusual for the apron to be intact while the back gutter is failing, or vice versa.
On a slated roof, soakers are used alongside step flashings. A soaker is a small piece of lead that sits under each individual slate at the side of a chimney or abutment. Soakers are invisible once the slates are laid back but they do the work of directing water away from the joint. If soakers are missing or have corroded through, the step flashing alone will not keep the roof watertight.
On a flat roof, lead is used at upstands where the felt or EPDM membrane meets a vertical surface, at drips over fascias, and at the junction with any adjacent pitched roof. Lead upstands on flat roofs are an area where cheap repairs often go wrong: the lead needs to be turned up the wall far enough (at least 150 mm above the finished roof surface) and fixed at the top before the chase is pointed.
These questions will quickly show you whether the roofer in front of you understands the full scope of the work or is planning to do the minimum. A good roofer will welcome these questions and answer them without hesitation.
Mildenhall Roofers carries out lead flashing, valley and flat roof lead work in Bury St Edmunds and the surrounding area. Lead should always be dressed by hand to the correct Code and properly secured. If you have a leak you think is coming from a flashing, a valley or a flat roof edge, get a roof survey so you can find out what is going on and what it will take to fix it properly.
No obligation · We'll call you to arrange a free visit
Call any time. Calls are answered day and night and passed straight to our roofers.
