Thatch a roof

Tie bundles of reeds or straw in overlapping rows, layered like a bird's feathers, so rain runs off for years.

hard⏳ a weektradition — not yet hand-tested

A roof of grass sounds flimsy, and yet a well-laid thatch keeps a family dry for twenty to fifty years. The secret is the same one a duck uses: thousands of stems all pointing downhill, each overlapped by the ones above, so a raindrop can only ever run outward and down. This is patient work, not strong work — every bundle is light, there are simply hundreds of them, and each must be tied down as if the next storm were coming tonight.

You need

• A steep frame — the roof must slope at 45 degrees or more (steeper is better). On a shallow roof, water dawdles, soaks in, and rots the thatch in a year or two.
• Battens — thin horizontal poles lashed across the rafters about a forearm apart. Every bundle ties to these.
• Thatching material, a lot of it — water reed, long rye or wheat straw, sedge, or tough long grass; stems at least arm-length, cut dry and kept dry. A small hut swallows a stack the size of the hut itself.
• Plenty of strong cordage — every course is tied on; you cannot have too much.
• Sways — long straight rods (hazel is ideal) laid across each row of bundles to clamp them down.
• Spars — green hazel or willow sticks, split, sharpened at both ends, twisted into a hairpin: the wooden staples that pin the ridge.
• A flat board or paddle — for tapping the cut ends of the stems even and tight.
• A ladder and a calm day — never thatch in wind.

Steps

1. Make the bundles. Gather stems into bundles as thick as your leg, all butts (the thick cut ends) at the same end, and bind each tightly near the butt. Shake out short and rotten stems.
2. Lay the first course at the eaves (the bottom edge of the roof): bundles side by side, butts pointing down and sticking out past the wall a full forearm, so drips fall clear of the wall face.
3. Tie everything down. Lay a sway rod across the course, then lash it to the batten beneath at every hand-span, sewing cord right through the thatch. Pull each knot until the bundles squeak — a course you can wiggle is a course the wind owns.
4. Work upward in overlapping courses. Each new row sits higher and covers the ties and top two-thirds of the row below — only the bottom third ever shows. Tap the butts with your board so the surface lies even, like combed hair.
5. Keep the thickness generous — about knee-deep (30 centimetres or more) measured straight in. Thin patches are where roofs fail first.
6. Do both sides evenly, course by course, so the frame carries the weight in balance.
7. Cap the ridge. The top line where the slopes meet is the weak point. Bend flexible bundles over it like a saddle, then pin them with spar hairpins pushed into the thatch below, in a criss-cross row on both sides.
8. Trim and comb. Cut the eaves to a clean line and comb loose stems downward — every stray stem is a wick leading water inward.
9. Walk away and look. From a distance the roof should read as one smooth pelt, every stem pointing downhill. Fix any hollow or hump now, while the ladder is up.

Watch out

• Fire is thatch's one great enemy. Never let a chimney or fire pit send sparks near it; keep any flue tall (see the hearth guide before lighting anything indoors). A thatch fire cannot be stopped with a bucket.
• Wet material rots inside the roof. If reeds or straw got rained on, dry them fully before laying. Sealed-in damp becomes mould and collapse.
• A shallow pitch cannot be rescued by thicker thatch. Below about 45 degrees, rebuild the frame steeper or choose a different roof — bark, wood shakes, or turf.
• Skimping on ties is how whole roof-sides peel off in one gust. Tie every sway, every hand-span.
• Birds and rodents mine loose thatch for nests. Tight courses give them no purchase; check ridge and eaves each spring.
• Never work the roof alone. One person on the ladder, one passing bundles and steadying it. Falls, not storms, are the thatcher's real danger.

How it works

Each stem is a tiny pipe angled downhill, and water clings to surfaces — so a drop runs stem to stem, always outward and down, and leaves at the eaves. The steep pitch keeps it moving too fast to soak in; the overlap means every path leads out. Trapped air between the stems also makes thatch a wonderful blanket — warm in winter, cool in summer.