Roof battens need replacing when they can no longer hold the tiles or slates safely: when the timber has gone soft, when it has split along its nail holes, when it was too thin for the job in the first place, or when the whole covering is coming off anyway. A batten that is dry, firm and straight can carry on doing its work for a long time, and a roof does not need new battens just because it is old.
Battens are the rows of sawn timber fixed across the rafters. Each course of tiles or slates hangs from one, hooked on by the tile's nibs (the small lugs on its back edge) or nailed through. If a batten fails, the tiles on it move. That is why a single slipped tile can be a sign of something bigger, and why we look underneath before we say what a repair involves.
This guide covers the signs of rot and weakness, what undersized or wrongly spaced battens look like, when a local repair is enough, why re-battening goes with a re-tile, and how the new battens and tiles are fixed under BS 5534.
How a batten fails under the tiles
A batten fails for one of three reasons: water from above, damp from below, or the nails that hold it. Each leaves its own marks on the timber, and knowing which one you are looking at tells you how far the problem goes.
Water getting past the covering
Under the battens sits the underlay, a membrane that catches any rain or snow driven between the tiles and runs it down to the gutter. When old bitumen felt goes brittle and tears between the rafters, water that should drain away soaks into the timber above it instead. Every wet spell then feeds the same patch of wood. The batten darkens, softens and loses its grip on the nails.
Condensation from below
A loft that cannot breathe can rot battens from the other side. With an HR (high resistance, so non-breathable) underlay over a cold roof, Marley's guidance on BS 5250 calls for an eaves gap of 10mm along the length of the eaves on pitches of more than 15°, and 25mm on pitches of 15° or less. Where insulation has been pushed hard into the eaves and blocked that gap, warm moist air settles on the cold timber and underlay, and the damage spreads across a whole slope rather than one spot.
Nails that rust through
Sometimes the batten is fine and its fixings are not. A corroded nail head snaps, the batten lifts off the rafter, and the course of tiles above it sags. The timber may look healthy from the loft, which is why we check the fixings as well as the wood, and photograph both for you.
Rot you can spot from the loft
You can learn a lot about your battens without going on the roof. Take a torch into the loft on a dry day, stand on the joists or boarding, and look up between the rafters.
What to look for inside
- Dark, wet-looking timber, especially low down near the eaves or around a chimney, where water collects.
- Daylight showing through gaps where a tile has slipped or cracked.
- Sagging underlay that hangs in pockets between the rafters, or has torn and dropped away completely.
- Black mould spots on the underside of the timber and underlay, a common sign of condensation.
- Rusty nail heads poking through, or orange streaks running down from them.
If you can safely reach a batten, press it gently with a screwdriver. Sound timber resists. Soft, spongy or crumbling timber has started to rot. Never lean on a batten or step off the joists to test one.
Signs you can see from the garden
From the ground, look along each slope. A course of tiles that dips in the middle, a wavy line where the rows should run straight, or slipped tiles in several places on the same slope all point to battens or fixings that have given way. One slipped tile on its own is usually a single failed nail or nib. Several in a line suggest the batten behind them has gone. Our guide to slipped roof tiles explains how to tell those two apart.
Where the underlay has failed but the battens are still firm, the order of work changes, and the survey photos show you which case you have.
Undersized, split or poorly spaced battens
Not every faulty batten is rotten. Some were never right for the roof they are on, and those show up most clearly when the tiles are lifted.
Too thin for the job
A batten has to span the gap between rafters and carry the weight of the tiles, the person fixing them and the wind trying to lift them. The right size depends on the rafter spacing and the covering, and BS 5534:2014+A2:2018, the current standard governing slating and tiling work, sets out how battens are specified. Older roofs and past patch repairs sometimes used thin offcuts or whatever timber was to hand. A thin batten bows between rafters, nails pull out of it more easily, and a heavy covering such as clay or concrete makes that worse.
Split along the nail line
Nailing too close to the end of a batten, or into dry timber with oversized nails, can split it. A split batten still looks whole from below but holds its nails poorly. On a slate roof, where every slate is nailed rather than hung, splits matter more.
Spacing that does not match the tile
The distance between battens, called the gauge, decides how far each tile overlaps the one below. That overlap is what keeps rain out. If battens were set at the wrong gauge for the tile, or a later repair used a different tile on the old gauge, the overlap can be short and rain can get through even when every tile is in place. The tile maker's data sheet gives the gauge for that tile at that pitch.
None of these faults can be fixed by refixing the tiles. The batten itself has to change.
When a local batten repair is enough
If the rot or damage is confined to one area, such as below a slipped run of tiles, around a chimney or at a valley, you do not need a new roof. A local batten repair keeps the rest of the covering in place.
What the repair involves
We strip the tiles or slates from the damaged area and set them aside. The failed lengths of batten come out, and new lengths go in, each joined over a rafter so no end is left hanging. If the underlay beneath is torn, a section is let in and lapped under the sound underlay above so water still runs outwards. The tiles then go back on the new battens, with any broken ones matched and replaced.
On slate, the same applies, though each slate has to be refixed through the batten. Where one slate has broken and the battens behind it are sound, the job is far smaller.
What the national guides show
National cost guides price small tile jobs rather than battens on their own. Which? puts replacing up to six standard tiles that are broken or gone at £75-£400 per job, ex VAT (Nov 2025, typical UK range). MyJobQuote gives about £215 for replacing five roof tiles (Oct 2026). A batten repair adds the work of stripping and relaying a larger area, so the size of that area and the access to it drive the price.
A local repair makes sense when the battens either side of the damage are firm. If we find soft timber spreading across the slope, patching one area just moves the next failure along.
Why re-battening goes with a re-tile
Once every tile is off a slope, the battens are fully exposed and cheap to renew compared with the cost of stripping the roof a second time later. Reusing old battens under a new covering is a false saving: the new tiles may outlast the timber they hang on.
Stripped to the rafters
On a full re-roof the covering, battens and old underlay come off together. The rafters are checked, a new underlay is laid, and new battens are fixed at the gauge the new tile needs. Our guide to the breathable roof membrane explains how the underlay choice affects loft ventilation. If the old tiles are hard and sound, they can be relaid on the new battens.
| Covering | Typical life, as published |
|---|---|
| Clay tile | HomeBuilding 60-80 years |
| Concrete tile | HomeBuilding 40-50 years, plain or Double Roman |
| Welsh slate | HomeBuilding 100+ years |
Approval and weight
On the Planning Portal's test, re-roofing work that touches under 25 per cent of the building envelope, and under 50 per cent of the roof area, normally needs no building control application. Choose a covering that adds 15 per cent or more in weight and the position changes: Building Regulations approval applies, with the rafters to be looked at by a structural engineer or surveyor ahead of the start.
For a whole three-bedroom roof, Which? gives £7,000-£21,000 ex VAT (Nov 2025) and HomeBuilding £10,000 to £15,000 for plain concrete tiles (Sep 2025). Both are typical UK ranges, and the sources sit a long way apart, which is why the size, covering and access of your own roof matter more than any national average.
Fixing new battens and tiles to BS 5534
The BSI lists BS 5534:2014+A2:2018 as current; it is the code covering slating and tiling of pitched roofs. It covers how battens are fixed to the rafters and how tiles and slates are fixed to the battens.
Is BS 5534 the law?
No. Marley puts it directly: "Installing to BS 5534 isn't required by law". Approved Document C, paragraph 6.8, under the Building Regulations, wants every tile, sheet and roof section fixed appropriately. We work to BS 5534 because it sets out, in detail, what an appropriate fixing looks like for each covering.
Mechanical fixing at the ridge and verge
The 2014 revision changed how ridges and hips are held down. Marley explains that since that revision, mortar alone is no longer relied upon to hold the ridge and hip tiles against the wind. Mortar is not banned and is still used, but each ridge and hip tile is also mechanically fixed, or a dry-fix system is used instead. BS 8612:2018 covers the testing of dry verge, hip and ridge systems. Our guide to dry ridge or mortar sets out the choice.
Slate on new battens
Under BS 5534, as Cupa states, natural slate requires a minimum pitch of 20 degrees, and Cupa recommends against hook fixings where the slope is below 25º. On a shallower slope, slates are nailed to the batten, so the batten has to be thick enough to take the nail without splitting.
On our pitched roofing jobs, we check every batten fixing before the first course goes on.
