Question answered
Rotten roof battens: signs and repairs
The short answer
Rotten roof battens show up from the loft as dark, soft or crumbling timber, and from the street as tile lines that dip or wave and tiles that keep slipping. If the rot sits around one old leak, that section can be stripped and re-battened. If it runs across a slope, or the underlay has gone too, the tiles must be lifted and the slope is, in effect, re-roofed.
Battens are the thin timber laths every tile hangs from. When they rot, the covering above them loses its grip. This page explains the warning signs and when a patch stops being sensible.
What a batten does, and why it goes soft
A batten is a narrow strip of timber fixed across the rafters, running level along the slope. Each course of tiles hangs from one, so a batten carries the weight of the covering and anchors it against the wind. They lie under the tiles, normally over a layer of underlay, which is why nobody sees them from the ground.
Timber rots when it stays wet. On a roof that nearly always traces back to one of two causes. Either water has been entering for years, through a split valley, a failed flashing or a run of cracked tiles. Or moist indoor air has condensed against the chilly underside of the tiles, which is how a loft without airflow can rot battens on a roof that has never leaked. Our answer on underlay and roof ventilation covers that second route.
Many older roofs were battened in untreated softwood, so simple age works against them too.
Warning signs from inside the loft
Choose a dry day, take a good torch up the hatch and step only on the joists. Healthy battens are pale to mid brown and feel hard. Trouble looks like timber turned black or grey, a surface cracked into small cubes like charcoal, white threads of fungus and a musty smell.
Look at the nails as well. Rust streaks running down from the nail heads, or tile nails that have drawn out and dangle, show the batten no longer grips them. A thin blade pressed lightly into the underside should meet firm resistance. If it sinks in, the strength has gone.
Then notice where the rot sits. A patch the size of a dinner plate beneath a chimney or valley suggests one old leak. Dark, damp battens along the whole eaves line point to something wider, perhaps underlay that has slumped into the gutter, as covered in eaves felt support.
Clues from the pavement and the garden
A fair amount can be learned without a ladder. Stand well back in low, raking light and sight along the slope. Tile lines that sink between the rafters, or a surface that looks rippled, may mean the battens under it have sagged. A tile that keeps slipping after being reset, or a patch where the same few work loose in every blow, suggests the nails have nothing sound to bite into.
Debris is another clue. Broken tile or loose nails turning up in the gutter after a gale tell you the fixings are letting go. A pair of binoculars, or a phone's zoom lens, used from the ground, shows more than many owners expect, and a steady hand with a phone captures the detail for later.
Do not climb up to investigate. A rotten batten will not carry a person, and the tiles over it can drop away under a boot. Dated ground photographs let us plan the loft inspection before we arrive.
A patch, or the whole slope
How far the rot has travelled decides the job. When damage is confined to a small area round a known leak, the tiles above can be lifted and stacked, the bad battens cut out, new treated ones fixed and the same tiles relaid, with a spare for any that crack. That is a sensible, modest repair, and the source of the leak is dealt with in the same visit.
If the rot crosses a slope, or each lifted section reveals more wet timber, patching only moves the problem along. The same holds when the underlay has perished, as described in torn or perished felt. At that stage it is cleaner to strip the slope and re-batten it fully, fixing the underlay and the edge tiles properly as they go back.
Our advice is whatever small repair ends the fault for good, and the survey photographs let you see where your own roof stands.
Where re-battening meets the re-roof thresholds
Re-battening a whole slope amounts to re-covering it, so Building Regulations enter the picture. The Planning Portal puts the dividing line at under 25 per cent of the building envelope and under 50 per cent of the roof affected: stay inside both and a building control application is not normally needed. Past either figure, approval is required and an insulation upgrade to the roof may follow.
On a bungalow or a terrace, one slope can be a big share of the roof, so it pays to check the sums early. Consent is explained to you, and we file the building control notification when the work needs one, so nothing is left for you to chase.
After the visit the written quote reaches you with pictures of the timber, and it gives a single total. Whichever roofer you ask, find out whether their figure includes scaffold and VAT. The wider range of tiled-roof work sits on our pitched roofing page.
Batten rot: two further questions
Can new battens go in without lifting any tiles?
Not properly. The tiles hang from the battens, so the covering over any section must be lifted, stacked and relaid. A new lath pushed in from the loft side cannot be nailed through to the rafter correctly and will not carry the tiles. Short, careful sections are possible, but the tiles always come off.
Why did nobody spot the rot at the last roof check?
Rot develops slowly and hides beneath the tiles, so a look from the road can miss it. A leak that began after a storm, or a loft insulated later without airflow, can also change conditions quickly. Photographs taken from inside the loft show the true state of the timber.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
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