Should Our Small Flat Roof Be Lead, or Something Modern?

Lead is the traditional answer on bays, porches, dormers and period buildings. Here is when it earns its price and when it does not.

Lead is at its best on small, visible, detailed roofs: bay window tops, porch canopies, dormer cheeks and roofs, and flat areas on listed or period buildings where a rubber membrane would look wrong. It shapes around awkward details without joints and, laid properly, lasts for generations.

On a large plain garage or extension roof, EPDM or GRP will usually do the same job for much less money. Our flat roofing systems comparison covers those.

Lead sheet is graded by code, with thicker codes used for flat roofs and gutters than for flashings. Crucially, each sheet or bay must be kept within a maximum size for its code, because lead expands and contracts with temperature. Bays are joined with wood rolls and drips that let each piece move freely.

Most early failures we see come from bays that are too large, sheets fixed too tightly, or missing drips on long runs, all of which lead to splitting.

Lead needs a smooth, well ventilated deck and a suitable underlay. On the underside, trapped condensation can cause corrosion that attacks the sheet from below, so ventilation and the build up of the roof are part of doing the job properly, not an extra.

Lead is valuable, and theft from roofs does happen. On exposed or commercial buildings some owners choose a lead alternative or a high quality GRP or EPDM finish for that reason alone, and that is a reasonable decision.

A single split can often be repaired by lead welding or replacing a bay. If splits keep appearing across the roof, the bay layout is usually wrong and patching will not stop it.

Is lead better than EPDM on a flat roof?

On small detailed or period roofs it often is. On large plain roofs EPDM or GRP normally gives similar performance for much less cost.

Why has my lead flat roof split?

Usually because the bays are larger than the lead code allows, or the sheet has been fixed so it cannot move with temperature.

Can lead go straight onto old boards?

It needs a smooth, sound deck with a suitable underlay and ventilation, so old boards are checked and often replaced.

Is there anything I can use that looks like lead?

There are lead alternative sheets and coloured membranes. Whether they are acceptable depends on the building, especially if it is listed.

Whether it is a bay, porch or dormer, we will tell you honestly if lead is worth it or if a modern system does the job for less.

Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.