Choosing the right material for flashings and valleys in Harleston makes the difference between a repair that lasts decades and one that needs revisiting within a few years.
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Lead work covers every junction, abutment and valley on a roof - the points where different surfaces meet and where water is most likely to find a way in. The material used at these junctions is not interchangeable. Different metals and products behave differently in service, and what suits one situation may be wrong for another. This page runs through the main options honestly, including where each one falls short.
If a roofer never mentions alternatives or explains why they have chosen a particular material, that is worth querying. A good tradesperson should be able to explain what they are using and why it suits your roof.
Traditional milled lead sheet is still the material most experienced roofers reach for when the job allows it. It has been used on British roofs for centuries because its properties are genuinely suited to the work: it is soft enough to dress tightly around complex shapes, it weathers to a stable patina that resists corrosion, and it moves with thermal expansion without cracking when installed correctly.
Lead is graded by code number, from Code 3 to Code 8. The heavier the code, the thicker the sheet. Selecting the right code for the application is part of the skill - using undersized lead in a high-wear position such as a valley means it will thin and pit sooner than it should.
One practical point: lead installed without expansion joints - typically, sections kept to around 1.5 metres with dressed overlaps - will eventually split as the metal cycles through expansion and contraction. This is one of the most common causes of premature lead failure, and it is entirely avoidable with correct practice.
Pressed aluminium flashing strips and flexible lead-effect products are widely available from builders' merchants. They are cheaper than traditional lead and faster to fit, which is why some roofers use them on smaller or more budget-sensitive jobs.
For a straightforward abutment on a modern tiled extension, a quality aluminium product fitted properly can be adequate. For a chimney stack with multiple faces, a complex valley, or any heritage or listed property, traditional lead is the appropriate choice.
Zinc sheet is sometimes proposed as an alternative to lead, particularly on contemporary or flat-roofed buildings. It is lighter than lead and has a distinctive blue-grey appearance that some homeowners prefer aesthetically.
Zinc is not a like-for-like substitute for lead on a traditional pitched roof. It has a different role and requires a different approach. For standard domestic lead work - flashings, valleys, soakers - traditional lead remains the more practical and better-understood material for most properties.
Mortar fillets - a wedge of sand-and-cement applied around the base of a chimney or along an abutment - are sometimes used instead of lead flashing. They are cheaper and faster to apply, but they are not a long-term waterproofing solution.
Mortar cannot flex. As a chimney stack and roof structure move independently with temperature changes and settlement, the mortar cracks. Once cracked, water tracks behind it and the damage to the roof and internal structure can be considerable. A mortar fillet that looks sound from the ground may already be cracked and letting water through at the back.
If your property has mortar fillets rather than proper lead flashings, that is worth flagging when you have a roofer inspect the roof. The question to ask is whether the fillet is an original or a repair - and whether proper lead should be installed in its place.
Soakers are small pieces of lead, cut and folded to sit under each course of tiles at an abutment - where a roof slope meets a vertical wall, for example alongside a chimney or dormer. Each soaker slots under a tile and up the wall face. A separate cover flashing, tucked into the mortar joints above, then laps down over the soakers.
This two-part system - soakers beneath, cover flashing above - is more effective than a single flashing alone because it creates a rebated waterproof joint that sheds water even under wind pressure. If a roofer installs a cover flashing without soakers at an abutment, ask why. In most situations, soakers are the correct detail.
The purpose of a lead flashing is to bridge the gap between two different roof materials or between the roof covering and a vertical surface, and to direct water away from that joint rather than into it. Without correctly formed flashings, water collects at junctions, works under tiles and into the roof structure, and causes timber rot and internal damp.
On a chimney, for example, the front apron flashing diverts water around the base of the stack. The step flashings up the sides prevent water tracking in under each tile course. The back gutter, fitted in the angle between the stack and the uphill roof slope, is the most critical element - it collects a large volume of water and must be deep enough and correctly formed to carry it clear.
Before agreeing to any lead work, it is reasonable to ask:
A roofer who answers these questions clearly and specifically is giving you the basis to make an informed decision. One who cannot explain the detail is worth approaching with caution.
We carry out lead work in Harleston and the surrounding area, covering properties in Diss, Scole, Pulham St Mary and neighbouring villages. If you are not sure which material or approach is right for your roof, call us and we will talk you through what we find and what we recommend before any work is priced.
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Call any time. Calls are answered day and night and passed straight to our roofers.
