A slate roof that has started to shed slates does not always need replacing. Often the slates are sound and what has failed is hidden: the nails holding them, the battens they hang from, the underlay beneath, or the lead at the chimney and the valleys. Re-slating is the job that deals with all of that together. The slates come off, the structure under them is checked and renewed where it needs it, and the slates, or new ones, go back on to a proper setting out.
The work follows a sequence, and each stage depends on the one before. Strip carelessly and slates that could have been saved break. Skip the battens and a new covering is hung from old, tired timber. Get the headlap wrong for the pitch and the roof can let driven rain in from the day it is finished.
This guide walks through the stages in the order a slater works, including what to ask at each, where the rules touch the job, and what moves the price. Roofs differ, so treat it as a map rather than a specification.
Deciding that re-slating is the right job
Before anything else, ask whether a repair would do. One or two slipped slates, a split valley or a failed flashing can be put right without lifting the roof, and when that is the case we tell you. Re-slating becomes the better choice when the faults are widespread: slates slipping across several slopes, nails rusting through in many places, battens soft or snapped, or patching that has been repeated until the roof is a patchwork.
Why does it matter? On a slate roof, each repair means walking on slates that are already loosely held, and each one risks more breakage. When the fixings have gone across a whole slope, repairing slate by slate costs more over the years than starting afresh. Our guide to slate roof repairs explains the cases where a repair is enough.
What the survey looks for
From the ground, and then from ladders and the loft, we look at how many slates have slipped, whether the heads of the slates have broken off around the nail holes, what the battens and rafters look like from inside, whether daylight shows through, and whether the underlay is present at all. Many older roofs have none, or a perished bitumen felt.
We photograph what we find and show you the pictures. Where the slates are good and the nails are what gave out, the plan is to strip and relay the same slates. If the slates are also delaminating or crumbling, new ones are needed. The decision is made on evidence from your roof, not a rule of thumb.
Scaffold, stripping and salvage
Every re-slate starts with access. A safe scaffold around the house, with a licence for any part on the public highway, goes up first, and it is a real cost: MyBuilder gives about £850 to £1,200 for a standard two-storey house, with chimney scaffolds at £400 to £900 on top (updated 21/08/2026). The scaffold firm applies for that licence, which in this area is issued by West Sussex County Council, or by Brighton & Hove in the city.
Stripping then goes from the top down, a course at a time. Ridge tiles, hip tiles and lead come off first, then the slates, which are sorted on the ground. Good slates are stacked by length and width; cracked, chipped or laminating ones are discarded. On an old roof the salvage rate is a useful early indicator of whether the existing slate is worth keeping.
Why salvage matters
Reusing your own slates keeps the roof's character, and on an older house or inside a protected street that can be a condition of consent as much as a preference. The slates were chosen, cut and weathered together, and they will not be matched exactly by anything bought later. Where there are not enough to cover the roof, the best slates go on the front slopes and reclaimed or new slates of the same size cover the gap on the back.
Stripping also shows what the roof was hiding: rot in the battens, old repairs, poor lead, a sagging rafter. Those are discussed with you when they appear, with photographs, and the written quote allows for what the survey expected to find. Anything beyond that is agreed with you before work goes ahead.
Battens, rafters and underlay
Once the roof is open, the structure is checked. Battens are the cross-timbers fixed over the rafters, and the slates hang from them. On most re-slating jobs we renew them as a matter of course, because old battens that grip nails poorly can undo the whole job. Fixing new slates onto soft or split timber defeats the purpose of the job. Rafters, ridge boards and wall plates are looked at as well, and any that have decayed are repaired or sistered.
The spacing of the battens is not arbitrary. It follows from the slate length and the headlap chosen for the pitch, so the setting out is worked out for the roof before the first batten goes on. A batten gauge set a few millimetres wrong shows as a creeping error by the ridge.
The underlay
Underlay is a sheet laid across the rafters under the battens. It catches wind-driven rain and snow that gets past the slates and leads it to the eaves. Many Victorian and Edwardian roofs have none. Fitting it during a re-slate is far easier than adding it later, and it improves the roof's resistance to weather. Our page on underlay and sarking for slate goes further.
Underlay also touches ventilation. A cold roof needs air to move through the loft, and the product you choose sets how much ventilation at the eaves is needed. Marley's reading of BS 5250 is a continuous eaves gap of 10 mm above 15 degrees of pitch, and 25 mm at 15 degrees or below, where the underlay is the high-resistance kind. We check that against your eaves, and where insulation has been pushed hard into them, we deal with it.
Pitch, headlap and how the slates are set out
The pitch decides how much overlap each slate needs. The overlap, called the headlap, is the depth by which a slate is covered by the one two courses above it. Steeper roofs shed water quickly and need less of it. Shallow roofs need more, because rain can be driven or can creep upslope between slates.
Cupa Pizarras, a slate maker, publishes figures for sheltered and moderate sites. For a 500 x 300 slate it gives 115 mm at 20 degrees, 105 mm at 22.5 degrees, 95 mm at 25 degrees, 85 mm at 27.5 degrees, 80 mm at 30 degrees, 70 mm at 35 degrees, 60 mm at 40 degrees, 55 mm from 45 to 75 degrees and 50 mm at 85 degrees. For 600 x 300 and 500 x 250 slates, the table gives no value below 25 degrees. On the same page, BS 5534:2014+A2:2018 is read as setting 20 degrees as the lowest pitch for a 500 mm natural slate at moderate exposure.
Why exposure shifts the numbers
Those values are for sheltered and moderate sites. An exposed roof can call for more, and the slate maker's own guidance and the product data sheet decide it. We do not give an exposure category for Worthing or any named street. We read the site, the pitch and the slate on offer, and set the headlap to the manufacturer's figure for them.
It follows that a re-slate is not simply the old pattern put back. If earlier work laid slates with too little headlap for the pitch, relaying to the same pattern repeats the fault. Our page on minimum pitch for slate gives the limits, and if a roof is too shallow for slate at all, we explain the alternatives rather than forcing it.
Nails or hooks, and lead, ridges and valleys
Slates are held either by nails through the slate or by hooks that catch its tail. Nails are the traditional fixing. Hooks are used on some roofs, but Cupa Pizarras advises against hooks anywhere below 25 degrees of pitch, and the maker's data sheet applies in every case. On an exposed coast the fixing is the part that decides how the roof handles a gale, so we specify it to the product, the pitch and the exposure, and the slate maker's instructions come first. Our page on hooks against nails sets out the trade-offs.
Beyond the field of the roof, the details do most of the keeping out of water. Slate roofs have lead at chimneys, abutments, valleys and soakers, the lead pieces dressed under each course. Leadworx reports that code 4 is now the usual lead for ordinary flashings and keeps code 3 for soakers only. Old lead that has split or lifted is replaced during a re-slate, since it will not be accessible again for decades.
The top and the edges
Since the 2014 revision of BS 5534, mortar by itself no longer holds the capping on a ridge or hip; each piece gets a mechanical fixing as well. Dry systems for those positions and for verges are tested to BS 8612:2018. On slate, a dry ridge system is often worth discussing, and our page on dry ridge on slate covers the question. At verges, the slates are bedded or fixed so the edge resists the wind that gets under a gable.
Valleys in lead or in a mitred slate pattern, hips and dormer cheeks all need finishing by hand. This is where most skill goes into a re-slate, and where a photograph during the work is most reassuring.
Regulations, consent, cost and the written quote
Re-slating is covered by the same thresholds as any re-covering. Two Planning Portal figures matter: 25 per cent of the total building envelope and 50 per cent of the roof. Stay inside both limits and no building control application is usually needed. Go past either one and approval applies; an upgrade to the insulation can follow, because Part L wants the entire roof element improved once more than 50% of its surface is renovated. We explain whether your job is notifiable and handle the Building Regulations notification with your building control body.
Planning is simpler. Planning permission is not usually needed to re-slate like for like. The exceptions are listed buildings and streets with an Article 4 direction that withdraws roof rights, and for those, check with the Adur & Worthing planning team first. Our notes on Victorian slate roofs cover the older houses where this arises most often.
What moves the price
In MyBuilder's slate guide (updated 21/08/2026), a re-slate runs at £100 to £180 per m², a typical UK range. On a real roof the total depends on the area and shape, the number of hips, valleys and dormers, the scaffold, how much slate can be salvaged, the battens and underlay, the lead and what the stripping reveals. Our guide to roof slate prices sets out the figures, and natural or man-made slate covers a choice that changes them.
Surveying comes first. A written quote with one total then reaches you, the photographs of your roof beside it, at pricing that is good and fair. Details of the slate chosen are in the quote, and we clear the site. For the whole picture of what we do with slate, see slate roofing in Worthing.
