How do I fit guttering to a shed?

Rain coming off an ungutted shed roof lands in a line about 300mm out from the wall, splashes back onto the cladding and soaks the bottom 200mm of it every time it rains. That band is exactly where a shed rots, and it is exactly what a gutter costing very little prevents. On a shed the gutter also has a second job: it collects usefully clean water for the garden.

Safety

What you'll need

• Mini or half-round gutter, the length of the eaves
• Gutter brackets
• Stop end, outlet and any joints
• Downpipe and clips
• Stainless or exterior-rated screws
• String line and a spirit level
• Fascia batten, treated (optional)
• Water butt and stand (optional)

Step by step

1. Give yourself something to screw into.Many sheds have no fascia — the roof boards simply overhang the wall. Screw a treated batten, 45 x 20mm or similar, to the rafter ends along the eaves. Brackets screwed into the edge of a 9mm roof board will pull out.
2. Decide which end the water leaves.Usually the end nearest where you want the butt, and away from the door. Mark the outlet position first — everything else is set relative to it.
3. Set the fall with a string line.Mark the high end so the gutter sits just under the line the water leaves the roof, then drop about 5mm per metre to the outlet end. Pin a string line between the two marks and set every bracket to it.
4. Keep the gutter under the roof line, not level with it.The back of the gutter should be higher than the front, and the roof edge should overhang into the gutter by about a third of its width. Water leaves a felt roof with some speed and overshoots a gutter set too low or too far out.
5. Fix the brackets at proper centres.No more than 800mm apart for mini gutter, and one within 150mm of each side of every joint and the outlet. Under-bracketed gutter sags between fixings and holds water and silt.
6. Clip the gutter in, working from the outlet.Clip the outlet in first, then work uphill. Check the insertion depth marks on the fittings — a joint pushed fully home has no room for expansion and will pop in summer.
7. Run the downpipe and support it.A short offset from the outlet to the wall, then pipe clips into the cladding at the studs. On a shed the downpipe usually goes straight into a butt, so the length is short — but it still needs a clip.
8. Set the butt on a firm, level stand with an overflow.A full butt weighs a great deal, so the stand must be on something solid. Fit an overflow — a hose from the butt's overflow outlet to a border or a soakaway — or a full butt simply spills at the base of the shed, which is the problem you set out to fix.
9. Test it with a hose.Run water along the whole gutter. Look for standing water at the high end, drips at the joints and splashing over the front. Adjust brackets now, while access is easy.

Tips

• Mini gutter is the right size for almost any shed. Full-size house gutter is heavier, costs more and needs stronger fixings for no benefit.
• On an apex shed, gutter both sides and join them with a swan-neck to one butt, or fit a linking kit between two butts.
• A leaf guard along the gutter is worth fitting under trees. On a shed you will not clean it as often as a house gutter, because it is out of sight.
• Take the downpipe outlet through a rainwater diverter if you want the butt to fill and then let the excess carry on down the pipe automatically.
• Fit the gutter before you treat the cladding, so you can treat the band behind it while you can still reach it.

Common mistakes

• Screwing brackets into the roof board edge — A 9mm board edge holds a screw for one wet winter. The gutter drops at one bracket, water runs to that point and pours out. Fix a fascia batten first.
• Setting the gutter dead level — Water sits in it, silt settles, algae grows and it becomes a trough of standing water that is heavier than the brackets were sized for. A small consistent fall is what makes it self-clearing.
• Letting the butt overflow at the shed base — The gutter was fitted to keep water away from the bottom of the walls. An overflowing butt puts it all back in one place, which is worse than no gutter at all.

Keeping on top of it

• Clear leaves and silt from the gutter and the outlet (Autumn, and spring if there are trees nearby)
• Check the gutter still falls to the outlet (Yearly)
• Check the butt overflow is clear and still discharging away from the shed (Yearly)

Questions people ask