How Heavy Are Concrete and Clay Roof Tiles?

Weight of a single tile

An individual tile is lighter than people expect. A small clay plain tile weighs in the region of one to two kilograms, because it is thin and compact. A large concrete interlocking tile, the sort used on modern estates, is heavier, often more than three kilograms, because it is bigger and denser. Natural slates are thin and light, and a slate of average size weighs less than a kilogram, though thick, rough-hewn slates weigh more.

Single-tile weight only matters when you are carrying them. For the roof structure, what counts is the weight per square metre of finished roof.

Weight per square metre

Per square metre, the figures are less obvious, because small tiles overlap more and need more tiles to cover the same area. Typical ranges are listed below. They are approximate and vary with the make, the lap and the batten gauge, so treat them as a guide.

The weight of battens, underlay and any water held in the tiles adds to this. Clay and concrete tiles absorb a little moisture, so a roof is heavier after rain. If you need an exact value for a structural check, use the data sheet for your tile.

Why the weight matters

The rafters, purlins and walls beneath a roof are designed for the covering that was there. Swap a light covering for a heavy one without checking, and you can overload the timbers, which then sag. The reverse also happens: stripping a heavy covering and replacing it with a lighter one means less load, but also less weight to resist wind uplift, which affects how many fixings are needed.

Roofs that are already dipping or bowed are a warning. Our answer on why a roof sags sets out the causes, and the structure should be looked at before more weight goes on.

The 15 per cent rule

Under the Building Regulations, a new covering that comes out at 15 per cent above the old weight, or higher, needs building control approval, and the structure may need strengthening (Approved Document A). So a switch from slate to concrete tile, or from concrete to clay, can bring in a regulatory step. Your building control body, which is the council team or a registered building control approver, can confirm what applies. We handle that side where the work is notifiable.

To compare materials beyond weight, see our guide on concrete versus clay roof tiles.

Weight and wind

Weight is a load on the structure, and it is also a resistance against the wind. A heavy tile is harder to lift in a gale than a light one, which is why heavy clay on a hilltop house needs fewer extra fixings than a light slate does. The standard fixing tables reflect that, and they also take account of how high and exposed the building is. A lighter covering is not worse, but it needs its fixings done properly.

If you are moving to a lighter covering to save load, tell us at the start. We can work out the fixing pattern for the new tile, and we can explain what that means for the nails and clips you will see on the finished roof.

Carrying and handling

Weight also decides how the job runs. A pallet of concrete tiles weighs a tonne or more, and it has to be lifted onto the scaffold or the roof in stages, and spread so it does not overload one rafter. The tiles are stacked over the walls where possible, not mid-span. If you are planning a re-roof, expect a delivery vehicle with a crane, and a clear place for the pallets to land.

How we check before we quote

On a survey we look at the roof structure from the loft, the sizes of rafters and purlins, signs of sag, and the covering already in place. If a heavier tile is on your wish list, we flag the question early and recommend a structural opinion where it is needed. We never guess at loads, and where a figure matters for the design we ask for it in writing from the tile maker. See our full tiled-roof service on the pitched roofing in Basingstoke page.