Roofing - Other FAQs
How do I calculate how many rolls of roofing underlay I need?
Measure the roof plane in feet (length × width) to get square footage, then add 10–15% for overlaps and waste. Divide the final square footage by 100 to find the number of roofing squares, and check roll coverage listed by the manufacturer (many rolls cover around 50–100 sq ft). Always round up and buy an extra roll for mistakes.
What type of flashing is best for a chimney on a pitched roof?
Step and apron flashings are commonly used for chimneys on pitched roofs. Lead was traditional, but lead‑free options like coated aluminium or flexible lead‑replacement flashings offer good performance and ease of installation. Use a secondary underlay or saddle for added protection in severe weather areas.
Can I use standard nails for all roofing tiles?
No. Use galvanised or stainless steel fixings depending on your environment. Coastal locations should use stainless steel to resist salt corrosion. Some tiles, especially clay or heavy slates, may require clips or screws specified by the tile manufacturer to avoid cracking and ensure secure fixing under wind uplift.
How much ventilation does my loft need?
A general guideline is to provide at least 1 square foot of ventilation for every 150 square feet of roof space if ventilation is unbalanced, or 1 square foot per 300 square feet when balanced between intake and exhaust. Split ventilation between eaves (inlets) and ridge or roof vents (outlets) to ensure good airflow and reduce condensation risk.
What are the signs my flat roof needs a new membrane?
Look for persistent pooling water, blistering or bubbling of the surface, visible seams lifting, and recurring leaks inside the building. Small cracks or worn patches can often be patched with liquid roofing, but widespread blistering or multiple seams failing usually means it’s time to replace the membrane.