Shed roofs leak for a small number of predictable reasons. Working through them in order will normally find the cause in an afternoon, and most are inexpensive to put right.

1. Fixings

This is the most common cause by some distance. Screws driven at an angle, overtightened until the washer is squashed out of shape, or left slightly loose, will all admit water. Washers also perish with age and UV exposure long before the sheet does.

Check every fixing for a clean, even seal. Replacements are straightforward: our roofing fixings range runs from 25mm to 210mm, and we include magnetic bit Tek drivers free on request with any order.

2. Laps

Side and end laps that are too short, or that have crept apart over time, let water track back under the sheet. On a shallow pitch this happens readily because water moves slowly and has time to find its way in. Our guide to overlapping roof sheets covers the dimensions.

3. Pitch

Sheds are often built with less fall than the roof covering really wants. Where the pitch is shallow, end laps need to be longer, and sealing tape or mastic in the lap stops becoming optional. If you are re-sheeting and can raise the pitch even slightly, it pays off.

4. Corrosion at cut edges and fixing holes

Any point where the protective coating has been breached will corrode first. Cut ends, drilled holes and scratches from installation are the vulnerable spots. Cutting sheets to length before they leave us avoids most site cutting, and we cut every sheet to your exact measurements as standard.

5. Flashings and trims

Junctions at ridges, verges and abutments are harder to get right than the open field of the roof, and they are where water concentrates. Ill-fitting or damaged flashings and trims are a frequent source of persistent small leaks.

When to patch and when to re-sheet

A single failed washer or a short lap is worth repairing. Widespread corrosion, multiple failing fixings or sheets that have lost their coating are usually telling you the covering has reached the end of its life, and patching will only postpone the work.

If you decide to re-sheet, send us your measurements. Sheets are made to order and delivered anywhere in the UK within seven days.