The short answer
Interlocking tiles are large and lock side to side, so each covers more roof and the job goes faster. Plain tiles are small, flat pieces overlapped course over course for the traditional rippled look. Some interlocking types work at pitches as low as 12.5 degrees, while plain tiles need a steeper slope. Typical UK costs per m² run higher for plain.
Two ways of covering a pitched roof, side by side: how they are laid, what pitch they need, how they look and what they cost.
How each tile works
An interlocking tile has grooves and ribs along its sides that engage with its neighbour, making a continuous run across the roof. The tiles are big, so fewer cover the same area, and each hangs on a batten by its nibs. Most are concrete, though clay versions exist, and they suit many post-war estates, where speed and consistency mattered.
A plain tile is small and flat or gently curved, and it does not lock to its neighbours. It works by overlapping: each course covers the joints of the course below, laid with at least a double lap so water has no straight route through. Plain tiles are traditionally clay and also made in concrete. There are many more on a roof, each held by nibs and usually a nail, with fixings following BS 5534.
That difference in shedding water shapes everything else. An interlocking roof relies on side locks and head lap, while a plain tile roof relies on a great many small overlaps. Both are sound when laid well, and both depend on battens, underlay and fixings behind them, as our answer on plain clay tile roofs explains.
Pitch limits and what the roof can take
The roof's slope is the first filter, because each product has its own floor. Marley's published figures show the spread. Its concrete Plain tile needs 35 degrees. Its Edgemere and Modern-Duo interlocking tiles need 17.5 degrees, its Double Roman 22.5, its Wessex 15 and its Mendip 12.5. Among clay, the Ashdowne needs 35 degrees, the Canterbury 40, and the Lincoln pantile goes down to 15.
The practical lesson is that interlocking tiles generally allow shallower roofs, which is why they were so common on lower-pitched houses. A plain tile on a shallow slope risks water being driven up under the laps in strong wind. If your roof is shallow and you like the plain-tile look, ask the roofer to test the pitch against the product before you commit.
Weight is the other question. Plain clay and interlocking concrete weigh differently, and moving from one to the other can add load. Under the Planning Portal's test, a covering 15 per cent heavier or more needs approval, so read our answer on changing roof tiles and weight before you switch.
How they look and how they age
Plain tiles give a finely textured roof with many small shadow lines, and hand-made clay carries natural shifts in colour, a look associated with older brick-and-tile villages. Interlocking tiles read as a broader, more uniform surface with bolder profiles. Neither is better; they suit different houses.
Ageing differs. Concrete tiles weather towards a duller, sometimes mossy face, and Marley puts their typical life at around 60 years while saying that is not a guarantee. For clay the quoted minimum is 60 years, a figure that is not a reliable guide for old peg tile. Moss and lichen settle on both. Concrete tiles can lose nibs with age, and our answer on broken tile nibs shows what that looks like.
Repairs follow the same pattern. A few interlocking tiles are easy to swap if a matching profile can be sourced. Plain tiles swap one at a time and reclaimed ones blend well, but with so many on the roof, matching colour and size takes more care. In a conservation area or on a listed house, the conservation officer may expect the existing material to stay, so ask the council's planning team first.
Cost per square metre and making the choice
From Checkatrade's October 2026 installation guide, typical UK costs are £120 to £230 per m² for plain tiling and £160 to £275 for clay. For repairs its June 2026 table lists concrete at £90 to £120 per m² and plain clay at £110 to £160, before VAT, for small areas. Plain costs more because more tiles, courses and nails go into the same area.
Treat those figures as yardsticks. What you pay depends on your roof's area, pitch, hips, valleys and dormers, and on how it is reached. One written total follows our survey, and it is wise to check whether any quote you gather includes VAT and scaffolding.
The choice comes down to pitch, house and budget. If the roof is shallow, interlocking is the sensible choice. If the house is older and the street is plain tile, matching it keeps the look. If you are repairing rather than replacing, stay with what is there unless the survey says otherwise.
Send a view of your roof from the road, plus the pitch if known, and we will explain which details we would examine first. Our pitched roofing page covers the wider choices.
More on this in Pitched Roofing Services in Crawley
Two more tile-type questions
Can I mix interlocking and plain tiles on one roof?
It can work on separate roofs, such as an extension, but mixing them on one slope looks odd and the pitch needs may differ. For a repair, find a tile of the same profile. If none exists, take sound tiles from a hidden slope for the visible side. The survey will show what is realistic.
Which type lasts longer?
Concrete is put at around 60 years, clay at 60 at least, never as a guarantee. How long a roof lasts depends on the fixings, battens, underlay, exposure and upkeep as much as the tile. A well-laid roof of either type outlasts a poor one, so ask what the survey says about yours.