A new roof and solar panels are usually bought a year or more apart, from different companies, and the order matters. Panels are held on brackets that pass through the covering to the rafters, so the roof under them is hard to reach once they are up. A tile that slips beneath an array, or a flashing that fails beside one, can mean taking part of the system down before anyone can repair it.
The sensible question is which job comes first, and what the roof needs before it carries anything extra. If the covering, battens and underlay are near the end of their life, replacing them first lets the panel fixings go into new work. If the roof is sound, there may be no reason to touch it at all.
This guide covers timing, the difference between in-roof and on-roof panels, where solar sits in the planning rules, the checks made on the roof beforehand and what moves the price. It deals with the roof side only. The panel design and the electrics belong to the company that supplies the system. For the wider picture of a full roof replacement, start on the main page.
Which job goes first, the roof or the panels
The cleanest answer is to renew the roof first whenever the covering is within a few years of the end of its life, then fit the panels onto the new work. Lifespans are published as ranges, never promises. Concrete tiles are often put at 30 to 60 years, one tile maker quotes a minimum of 60 years for clay, and natural slate at 80 to 100 years or more, all depending on exposure, workmanship and upkeep. A roof in the second half of its range, with panels bolted to it, is a roof you will want to reopen.
The reverse order is the expensive one. Lifting an array off to re-roof underneath means someone to disconnect and test the system, a second visit to refit it, and a spell without generation. Paying for the scaffold twice is the other sting. MyBuilder puts it at around £850 to £1,200 for a standard house of two storeys (updated 21/08/2026), and one erection shared between roofers and panel fitters is the simplest saving on offer.
When the roof can stay as it is
A sound covering does not need replacing just because panels are coming. If the survey shows tiles in good order, firm battens and an underlay that has not perished, the panel installer can work on it. We tell you so. The smaller repairs worth doing beforehand are the ones that are awkward to reach later: refixing loose ridge and hip tiles, renewing worn lead at a chimney, and clearing a choked valley.
Re-roofing with panels in mind
If you are replacing the roof and panels are likely within a few years, mention it at the survey. The slope the array will use and the route the cable will take are easier to plan while the slope is open than after the new covering is down.
In-roof against on-roof panels
On-roof panels, the common arrangement, stand a short distance above the covering on hooks or brackets screwed to the rafters. The tiles stay where they are, with the bracket passing through or under them. In-roof panels take the place of part of the covering instead. They sit in the plane of the slope, framed in a tray with flashings around the edge, and shed the rain themselves over the area they fill.
The difference matters most on a new roof. An in-roof system is a roofing job as much as an electrical one, because the waterproofing in that patch depends on the tray, its flashings and the underlay beneath. It is laid as the roof is covered, so it suits a full replacement far better than a retrofit onto an old slope. If water gets in under one, the tile layer that would normally shed it first is missing, which makes a leak harder to trace. Whoever fits it needs to understand how the surrounding tiles lap into the frame.
What on-roof fixings do to the covering
Every bracket is a penetration. On a tiled slope the tile is notched or swapped for a purpose-made type, and on slate the fixing has to be dressed or flashed. Done properly, the joint stays dry. Done badly, it is the first place water finds. Wind adds to the load, since panels catch it too. Marley points out that below a 30° pitch a windward slope can see severe suction, so an array sits on a surface already working hard. The tiles around it should follow the maker's fixing specification, and the ridge and hips are mechanically fixed to BS 5534 rather than left to mortar.
Roof type changes the plan
A low-pitched bungalow slope, covered in our guide to bungalow roof replacement, is easy to reach but sensitive to wind. On a block, the roof usually belongs to the building, not to one flat, which is why roof replacement on a block of flats starts with who has the right to decide.
Where solar sits in the planning rules
Solar panels are treated separately from other roof alterations. The permitted development class for alterations to a house roof, Class C, covers things like roof windows and rooflights, but its own exclusions in C.1(d) remove solar photovoltaic and solar thermal installations, alterations and replacements. Panels are governed by their own provisions, which we do not set out here. The class wording is in the General Permitted Development Order, Schedule 2 Part 1, and the Adur & Worthing planning team will tell you how it applies at your address.
The roofing half is a separate question
Putting back a covering that looks the same rarely changes how the house looks, which means that part seldom needs a planning application. Two caveats apply: a listed building, or an Article 4 direction that has taken the right away.
Directions that name solar panels
Two local conservation area directions mention them outright. In Old Shoreham and Kingston Buci, permission is needed for alterations to a house roof that faces onto a public way, and the directions list roof coverings, rooflights and solar panels among them. Warwick Place in Worthing removes roof alterations on its own frontage too. Elsewhere in a conservation area the ordinary rules still apply, but check before you order.
Listed buildings need consent for work that affects their character, and panels on a listed roof are a matter for the council's conservation officer. Where the house lies within the South Downs National Park, the Park's own Authority is the planning authority. A call before you sign costs nothing and avoids an enforcement letter later.
Roof checks before anything is fixed to it
Before panels go on, or before a new roof is specified around them, we look at what the weight and the fixings will bear on. Most of it can be seen from the loft and the eaves, and you get the pictures along with the quote.
Rafters come first. They are the timbers the brackets screw into, so we look for sagging between supports, old rot at the eaves and any rafter cut away for a chimney or a hatch. Our guide to roof timbers when re-roofing explains what happens when soft or undersized timber turns up.
Battens and underlay come next. Battens that have rotted, or been pieced from short lengths, will not hold a bracket properly. An underlay that has perished or torn lets water past any hole a fixing makes, and an old one is far better replaced while the tiles are off than after the array is up.
Joints and edges
We check the flashings at chimneys and abutments, the lead in valleys, and the bedding under ridge and hip tiles. Anything due for renewal within a few years is cheaper to deal with now than around a bank of panels. The same goes for verges, the roof edge at a gable, because panels near an edge take the most wind.
Ventilation in the loft
Condensation is a risk wherever the roof void cannot breathe. For a high-resistance underlay, Marley's summary of BS 5250 gives a continuous 10mm gap along the eaves on pitches above 15°. We check the eaves stay open and that nobody has pushed insulation over them. If the survey finds a fault, the quote deals with it as one total price.
Building Regulations, weight and the thermal upgrade
Re-covering a roof does not normally need a building control application where less than 25 per cent of the building envelope and less than 50 per cent of the roof is affected, says the Planning Portal. A full replacement of a main slope usually passes the roof limit, so plan on approval, through the council or a registered building control approver. Where the work is notifiable, we handle that step.
Passing the threshold can bring a thermal upgrade. Approved Document L wants the entire element brought up to standard once more than 50 per cent of it is renovated, and a new or replacement roof has a limiting U-value of 0.15 W/(m²·K). Plan the insulation with the roof, not afterwards, since the build-up can change the depth at the eaves where panel rails will sit.
Weight on the structure
Panels add load, and a heavier covering does too. A new covering 15 per cent or more heavier needs approval, according to the Planning Portal, which also recommends asking a surveyor or structural engineer first if the new tile is significantly heavier than the old. Approved Document A calls a loading rise of more than 15 per cent significant. Those figures concern the covering, not the array, so on an old or lightly built roof ask the panel company whether the structure has been checked for the two together.
Wildlife
The law protects bats and nesting birds, and a re-roof is among the jobs that can disturb them. Tell us if you have seen either in or around your roof.
Ask the panel company what notification their own part of the work needs. It is separate from ours and best settled before dates are fixed.
What shapes the price when the jobs are combined
The roofing cost follows the usual drivers: the roof's size and complexity, the new covering, the access and whatever the survey turns up. For a semi-detached house MyBuilder (updated 21/08/2026) gives typical UK ranges of £5,000 to £8,000 for a gable roof and £8,000 to £12,000 for a hipped one. Checkatrade (October 2026) shows £7,000 to £16,250 for a gable and £9,250 to £18,000 for a hip, plus VAT. They are national guides, not a price for your house, and the written quote follows the survey.
Planning around panels can add a little on the roofing side, such as extra battening, better underlay in the array area or neatly dressed flashings round a frame. It can also save money, mostly through one scaffold and one run of days on site.
Check what each figure includes
If you put a roofing quote beside one from a panel company, find out whether each includes VAT and scaffolding. A quote that leaves out the scaffold looks cheaper than one that carries it. If insulation is part of the job, the quote sets out how the VAT on it has been treated, because the rate turns on whether it counts as one supply or several.
Grants
Most homes will not find a grant that pays for a new roof. The government's Warm Homes: Local Grant lists solar panels among improvements a council arranges and pays for, for a household income of £36,000 a year or less, an EPC of D to G, and only where the council has funding. It does not mention roofs. The Housing Grants Team at Adur & Worthing Councils can say whether you qualify.
When panels are planned, we say whether the covering and flashings should be renewed first, so they need not be lifted again.
