New felt roof using 3-layer built up system
Flat roof repairs and renewals
This old felt roof had seen better days. It had been allowing small amounts of water into the property and was due for renewal. The boarding beneath the felt was bowed and sagging in multiple areas, causing water to pool in spots. Boards had to be repaired for a reliable, long-lasting roof. After removing the front felt drip edge, we discovered it had been constructed from old insulation sheets.
These straw insulation sheets were commonly used after World War II, known as “Stramit” insulation. Made from compressed straw, some versions contained asbestos for fire resistance, though none was found here.
We boarded over the existing structure to save cost and reduce risk of ceiling damage below.
Boarding over the existing roof
We re-boarded the roof using plywood sheets, secured through the insulation and into joists with special insulation nails. Joist ends were located and chalk lines snapped to guide board placement and nailing.
Each plywood sheet was temporarily laid, dips filled with expanding foam before final nailing. 3-inch arris rails were added to direct water to gutters.
Laying the felt
The first base layer of 3B underlay bonding felt was tacked onto plywood boards, providing a stable surface and temporary weather protection.
Felt nails or staples were fixed every 6 inches in both directions using a hammer tacker.
First torch on layer
The second felt layer was applied using a gas torch, running perpendicular to the first for strength and durability.
Disclaimer:
This work should only be carried out by qualified professionals with gas torch experience. DIY is dangerous; serious fire risk exists near roofs or timber structures.
Installing the drip edge
Timber battens were added along the drip edge and missing fascia replaced. Felt was folded and bonded to form the drip edge.
Top layer of green mineral felt
The final 4mm green mineral felt was installed side-to-side, extending under adjacent tiled roof edges.
The roof is now structurally sound, high-quality, and reliable. For flat roof repairs call us here.
See more on our roof repair page or browse previous projects.