Rotten roof battens
How do you know if roof battens are rotten?
The short answer
You can often tell roof battens are rotten from the tiles, because they sit unevenly, slip repeatedly or dip between the rafters. The battens are the timber laths that the tiles hang from, so when they soften the tiles lose their grip. Inside the loft, dark, crumbling or sagging timber confirms it, though the battens often show only once some tiles are lifted.
What battens do, the signs that point to rot, what causes it, and how a roofer replaces them without stripping more than needed.
What the battens carry
On a tiled roof the rafters are the sloping timbers, and the battens are the thin horizontal laths fixed across them. Each course of tiles hooks over a batten by its nibs or is nailed to it, so the battens hold the whole covering in place and pass its weight down to the rafters. Spacing is set by the size of the tile and how much each course overlaps the one below it.
Because they sit directly under the tiles, battens take the hit when anything goes wrong above them, and they cannot be inspected without lifting tiles. A small leak that never reaches the ceiling can soak a batten for months. Timber that stays wet softens, loses its grip on the nails and finally gives way. That is why a roof can look tidy from the street and still be weak underneath, and why we look at the battens whenever tiles are lifted for any other job.
Signs on the tiles
Start with the lines. A healthy slope has tile courses that run straight and level. Rotten battens let tiles settle, so you see waves across a slope, a dip between two rafters, or a course that no longer lines up with its neighbours. Tiles that slip again after being refitted are another strong clue, because the nails or nibs have nothing firm to hold. Loose nails and wind are the other usual reasons a tile moves.
Look closely at the moss. A thick band that follows one course may sit over a leak. Cracked tiles in a line can also mean a batten under them has dropped, putting a load on tiles never meant to carry it. None of this proves rot by itself. A tile that sounds hollow when tapped or a lift that comes away with no resistance is closer to proof, and the roofer should show you the timber in a photograph.
Signs from inside the loft
Where a roof was laid without underlay, as many older ones were, the battens show from the loft as a row of thin laths. Where there is felt, you usually see only its underside, and the evidence is indirect. Look for damp patches on the felt, stains on rafters, daylight through the covering, or dust and bits of grit on the loft floor that have dropped from above.
If you can reach the timber safely, press a screwdriver into it. Sound wood resists. Rotten wood is soft, dark and breaks into small cubes or fibres. A batten that crumbles under light pressure has little left to give a nail. Stay on the joists or a proper boarded walkway, never on the plasterboard between them. If you are not sure, take photographs and leave the probing to us. Our guide to a sagging roof explains when a dip points at rafters or the structure, and not only the battens.
What causes battens to rot
Water is the main cause, and it gets in by several routes. Torn or perished felt lets rain through. A cracked tile, a failed valley or a flashing that has pulled away feeds a steady drip onto one spot. Condensation forms on cold surfaces in a poorly ventilated roof space and wets the timber from below. Gutters that overflow soak the lowest battens at the eaves again and again.
Age plays its part as well. Older roofs may have timber that was never treated, or that has been damp so often it has little strength left. The fixings matter too, because nails that loosen in softened wood let the tile move. Coastal weather adds its own load, as gales pull at a loose covering and driving rain finds every gap, so a weakened batten is put to the test quickly. If you suspect more than one cause, our guide to underlay and ventilation covers how air movement and the felt layer work together to keep the timber dry.
Replacing battens, and what it costs
Battens cannot be changed from above without lifting the tiles over them. On a small patch, we strip only that area, fit new treated battens at the correct spacing and relay the sound tiles. Where rot has spread across a slope, re-battening the whole slope is the safer call, since new timber next to weak timber leaves a roof with uneven strength. Fixings follow the manufacturer's data and BS 5534, which Wienerberger summarises as at least one mechanical fixing for every single-lap tile.
Access and area decide the cost. Checkatrade's roof repair guide, updated in October 2026, gives roofers' rates of around £35 to £45 per hour or £280 to £360 per day. The written quote that follows our survey names one total. For the wider choice between patching and a new covering, see our guide to repairing or replacing a tiled roof, or the pitched roofing page for the full range of work.
Related questions
Roof batten questions
Can only the rotten battens be replaced?
Yes, when the damage is limited to a small area. The tiles over it are lifted, the timber is renewed, and the tiles go back. If the rot runs across a whole slope, renewing the full slope gives a more even result.
Should the felt be renewed when battens are replaced?
Usually it is worth doing, because the felt sits right under the battens and the tiles are already off. If it has torn, perished or sagged, new underlay costs little extra once the access is in place.