Our Unit's Flat Roof Keeps Leaking. What Are the Real Options?

Commercial flat roofs fail differently from house roofs and the decisions involve tenants, trading and budgets. A practical guide for building owners.

How commercial flat roofs fail

Large flat roofs on shops, offices, schools and small industrial units usually fail at the details first: upstands, outlets, parapet copings and plant bases. Ponding water where the deck has deflected speeds up wear, and foot traffic from contractors servicing plant punctures membranes.

A targeted repair suits a sound roof with a few defined failures. An overlay, where a new membrane goes over the existing covering, can be cost effective if the existing layers and insulation are dry. Where the insulation is wet or the deck is failing, stripping back is the only lasting answer.

A core sample or moisture survey shows which situation you are in, and it is money well spent before committing to a large contract.

Keeping the building open

Most commercial roof work can be phased so the building keeps trading. That means planning where materials are lifted, protecting entrances, and making each section watertight at the end of every day.

Clearing outlets and gutters, checking upstands and resealing small defects once or twice a year is far cheaper than dealing with water through a suspended ceiling. A simple roof log of what was found and done also helps when you come to sell or let.

Can you repair our roof without closing the business?

Usually yes. Work is phased and each area is made watertight daily so the building can stay open.

Is an overlay as good as a new roof?

It can be, provided the existing layers and insulation are dry and sound. A moisture survey tells you whether that is the case.

Why does water appear far from where the roof is damaged?

Water travels across the deck and between layers before it finds a way down, so the drip inside is rarely under the defect.

How often should a commercial flat roof be checked?

Once or twice a year, and after major storms, with outlets cleared each time.

Manage a building with a flat roof?

We will survey it, show you where it is actually failing and give you a written plan you can budget around.

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