Re-felt a shed roof

Strip the old felt, check the boards, then fit new felt in overlapping layers for a watertight shed roof.

RF-01Pick your day and gather materialsFelt only sticks properly in dry, mild weather, so check the forecast for a dry spell of at least a day, ideally above 10°C. Measure your roof (length x width of each slope) to work out how much felt you need, adding 100mm extra all round for overlaps and edges. Buy mineral felt in a roll, felt nails, felt adhesive, and a ridge cap strip.

1 roll · Shed roofing felt (mineral felt, 10m roll)

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1 250g box · Galvanised felt nails (20mm)

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1 2.5L tin · Felt adhesive/bonding compound

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1 each · Ridge cap felt strip

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RF-02Clear the roof and strip off the old feltRemove anything sitting on the roof and sweep off leaves and moss. Use a claw hammer to pull out old felt nails and lift the edges, then peel the old felt off in strips, using your utility knife to cut through any stubborn sections. Bag the old felt for disposal — most councils won't take large amounts in a normal bin, so check if you need a tip run or a licensed waste collector.

1 each · Claw hammer

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3 each · Heavy-duty rubble sacks

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RF-03Check the roof boards underneathWith the felt off, look for soft, dark or spongy timber — this is rot and it won't hold nails or support the felt. Press firmly with your hand; if a board flexes or crumbles, it needs replacing. Cut out rotten sections back to solid timber and fit new WBP plywood or feather-edge boards cut to match, screwed down every 300mm.

1 sheet · WBP plywood sheet (18mm)

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1 box of 100 · Decking/timber screws (50mm)

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RF-04Treat exposed timberBrush a coat of wood preservative over any bare or newly cut timber and let it dry fully before felting — this usually takes a few hours in mild weather. Don't felt over damp or wet wood, as moisture trapped underneath will cause rot later.

1 tin · Wood preservative (clear, 1L)

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1 each · Paintbrush

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RF-05Fit the first layer of feltStarting at the lowest edge of the roof, roll out the felt so it overhangs the eaves by about 40mm, and trim to length with your utility knife. Nail it down every 150mm along the edges using galvanised felt nails, keeping nails at least 25mm in from any edge so they don't split the felt.

RF-06Fit the remaining layers with overlapsWork up the roof in rows, overlapping each new strip by at least 75mm over the one below. Spread felt adhesive along the overlap before pressing the next strip down firmly, then nail it as before. This overlap is what keeps water running off the roof rather than under the felt, so don't skimp on it.

RF-07Dress the edges and gablesFold the felt down over the eaves and gable edges and nail it to the fascia or barge board every 100mm. Fit a timber or metal edging trim over the fold if your shed doesn't already have one — this stops wind getting underneath and lifting the felt.

2 length (2.4m) · Timber edging trim

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RF-08Fit the ridge cap and finish upFold the ridge cap strip over the apex of the roof so it covers both slopes equally, and nail it down every 150mm along both sides. Check all edges and overlaps are firmly stuck and nailed, then clear away offcuts and tools.

KNOW THE RULES

Before you start: Do I need planning permission for a garden room or outbuilding?

PART OF A BIGGER PROJECT

Refresh a garden shed

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