Nobody photographs roof battens for the estate agent. They are narrow strips of softwood nailed across the rafters, hidden under the tiles and out of sight from the loft unless you shine a torch along them. Yet every tile on your roof depends on one: it hooks over a batten, or it is nailed to one, and when the batten fails the tile goes with it. Battens are cheap, and a roof that is re-tiled on tired battens is a poor bargain. This guide explains what they are, what the grade marks mean, how spacing is worked out, and the signs that yours are on their way out.
What roof battens do
A batten has three jobs. It carries the weight of the tiles, passing it down into the rafters. It holds the fixings, since the nails or clips that keep tiles in place bite into the batten. And it sets the spacing of the courses, so that every row of tiles lies at the right distance from the next. Get any of those wrong and the roof suffers: a weak batten sags, a split batten loses its nails, and a batten at the wrong spacing leaves the headlap too short.
The battens run horizontally across the rafters, from one side of the roof to the other. Over them sit the tiles. Under them, usually, is the underlay, the membrane that catches any water that gets past the tiles and sends it to the gutter. Where a vapour-permeable membrane is used, a second set of battens may run up and down the rafters over the membrane, to create a drainage space, and these are called counter battens. Our guide to breathable roof membranes and underlay explains where those fit.
Sizes and what they are made from
Roofing battens are softwood, normally pine or spruce, cut square-edged and sawn rather than planed. The common cross sections are about 25 mm by 38 mm and about 25 mm by 50 mm. The wider, thicker section gives more bite for the fixings and more strength between rafters, and it is chosen where the rafters are spaced further apart or the tiles are heavy. The right size depends on the rafter spacing, the weight of the covering and the code of practice, and a supplier or roofer reads it from the tile data and the spacing of the rafters on site.
Sawn softwood is vulnerable to damp, so roofing battens are normally treated with a preservative. The treatment is often visible as a green or brown tint to the timber. Untreated battens are prone to rot where they are damp, and that is a common reason for failure on older roofs, which were often laid with whatever timber was to hand. Our guide to roof timbers places battens among the rest of the structure.
Grades and stamps: reading the markings
Run a torch along a new batten and you will usually find a stamp on it. The marking identifies the grade of the timber, the supplier, the treatment and the standard it was cut to. For roofing, the grading matters because it controls how many knots, splits and slopes of grain the timber can have. A batten with a large knot at the centre is weaker, and one with a split near the end will lose a nail. The tiling code of practice sets out what is acceptable for roof battens and says they should be graded and marked.
In practice, you should be able to ask a roofer three questions about the battens and get plain answers. Are they graded and stamped? Are they preservative-treated? And are they the right section for the rafter spacing on this roof? A roofer who cannot say what the battens are is probably not using good ones. Our explainer on BS 5534 and tile fixing shows where battens sit in the standard.
Spacing and gauge
Two distances matter. The first is the spacing of the rafters, which sets how far each batten spans. Most modern roofs have rafters or trusses at a regular spacing. The second is the gauge of the battens, the distance between one batten and the next up the slope. The gauge is set by the length of the tile and the headlap required: it is the tile length less the headlap, divided evenly over the slope. Get the gauge wrong and the tiles either run out of room at the ridge or leave too little overlap to keep out wind-driven rain.
The first and last battens are special. At the eaves, the lowest batten is set so the first course of tiles projects the right distance into the gutter. Near the ridge, the top batten is placed to carry the ridge tiles and any dry-fix system. A "tilting fillet" or eaves support is added at the bottom to lift the first tiles to the right angle. These details are where an inexperienced roofer's work shows first, and they are a good place to look when you are trying to judge a roof that has been re-done.
How battens fail
Battens fail in four main ways.
- Rot. Water from a leak, or condensation in a poorly ventilated roof, keeps the timber damp, and wet-rot fungi break it down. Rot is worst where leaks run along the underside of a tile, at valleys, behind chimneys and at the eaves.
- Snap and split. Old, dry battens go brittle. A tile slides, someone steps on the roof, and the batten breaks at a knot.
- Nail failure. The batten is sound but the nail has corroded or the nail hole has widened. This is the root of the trouble we describe under nail sickness.
- Insect attack. Woodworm can riddle softwood that has been damp for years. The holes weaken the batten and loosen the nails.
Often a batten shows more than one of these. A split batten also lets water in, which causes rot, which loosens the nails. That is how a small fault turns into a roof-wide one.
Signs your battens are going
You cannot see battens from the ground, but you can see what they do. Tiles that are slipping, sagging or lifting in lines along the roof point to batten trouble, because tiles slip in the row along a failed batten. A roof that looks wavy, with a dip across a slope, may have battens that have lost their strength. In the loft, a torch beam along the underside shows dark, soft or crumbling timber, orange rust at nail points, or battens that are visibly cracked. Pressing a screwdriver into the wood and finding it soft is a clear sign of rot.
Our guide to signs a tiled roof is failing lists the warning signs on the outside of the roof, and many of them lead back to the battens.
| What you see | What it may mean | Usual response |
|---|---|---|
| Row of tiles slipped along a line | Batten snapped or nails failed along it | Replace the batten and refix the tiles |
| Soft, dark batten in the loft | Rot from a leak or condensation | Find the water source, then replace the batten |
| Rust powder under tile nail holes | Nail corrosion | Refix with corrosion-resistant nails |
| Pin holes and fine dust | Insect attack | Assess the extent, replace affected timber |
| Wavy roof line | Weak battens or sagging rafters | Survey the structure before recovering |
Why we replace battens when we re-roof
When a roof is stripped for recovering, the battens go too, unless there is a good reason to keep them. There are three reasons. The old battens are holed by the old nails, so new fixings have less to grip. They have been through years of weather and are likely to be brittle. And their spacing was set for the old tile, and rarely matches the new one exactly. New, graded and treated battens at the correct gauge cost a small part of a re-roof, and they are the foundation of the new covering. Reusing them to save a small sum is a false economy, and any roofer who offers to do so should explain why.
There are exceptions. On a sound roof where only a patch is being repaired, existing battens that are in good order stay. On a listed or historic building, original timbers may be kept and repaired for the sake of the fabric, and any change should be agreed with the council's conservation officer. Our guide to roof work on a listed building covers the usual approach.
Re-battening and cost
Re-battening a roof without replacing the tiles is possible: the tiles are lifted, the old battens removed, new ones fixed and the tiles relaid. It is common when the tiles are sound but the roof has nail or batten trouble, as the tiles can be reused and the main cost is labour. A cost for this varies a lot with the size of the roof, access and how many tiles break on lifting, and we have no sourced typical UK range to quote, so we price it from the survey. The same applies to scaffold hire, which can be a large share of any pitched roof job. Our page on tiled roof repair costs sets out what is known.
The cost of not doing it is higher. Tiles laid on weak battens come off in the first big wind, and the repair that follows needs the scaffold again. If your roof is on its last legs, it is far cheaper to fix the battens once, properly.
What we do on a survey
We check the battens wherever we can see them: from the loft with a torch, at the eaves, at gaps where tiles have slipped, and under any tile we lift. We photograph what we find on your roof, and we tell you whether the timber is sound, patchy or past it. If a repair will do, we quote it. If re-battening or a full strip is needed, the report says why. The quote is fixed and in writing, the old battens and waste are taken away when we finish, and the work comes with our written ten-year guarantee on workmanship. To see how this fits into the rest of our work, read about pitched roofing in Basingstoke.
