• Lisa Gardener

Build Cost Basics: Roof Tiles

Tiles are a popular covering for pitched roofs, but there are lots of options to choose from. Plus, each style works best on specific roof pitches, so it's important to do your research before ordering.

Roof pitches

The most suitable topping for your self build to extension will be influenced by your budget, how the space will be used and, possibly, the thoughts of the local planning department. Other considerations include geographical location, building orientation and wind exposure on your site.

The roof pitch on a ground floor single-level extension is generally going to be lower than those on higher storeys - mostly because of its visual appearance and the practical element of needing to fit the roof below/between existing upper floor windows. But a pitch roof of 15° or less is unlikely to be tiled due to wind uplift and penetration by wind driven rain, particularly in areas of sever exposure.

As a rule, lower pitches require greater overlap between tiles, which means more units and therefore higher costs per m². Tile spacing on steeper designs is generally wider; although the price per m² will reduce, it will not make the roof cheaper overall because the steeper angle has a bigger surface to cover. However, the larger area beneath this can provide an opportunity to create additional living space.

Tile options

There are different styles and materials available to cover a pitched roof, but here are some popular solutions:

Pantiles: Featuring an S-shape profile, lapped tiles are available in various designs to create a roof with rolls and troughs. They are available in single and double tiles, non-interlocking and interlocking, clay and concrete. Some are suitable for pitches down to around 15°. These units are generally lighter and the most cost-effective in comparison to the other options. You can also get pantiles that simulate the look of plain tiles.

Plain tiles: Mostly made of clay, these flat designs require double lapping to prevent water penetrating the gaps between adjoining tiles, which can increase the load on the structure by as much as 50% more than interlocking units. The extra nailing requirements make a big difference to labour costs. Plain tiles are not generally suitable for pitches below 35°.

Slate: These units need at least double lapping for a watertight finish. They usually require a pitch of 30° or more; larger sizes are suitable for lower designs as they are heavier, but they are also more expensive.

Estimating costs

The prices shown below are presenting a 12m x 8m house and 5m x 5m extension project, both with apex roofs. The costs include the labour and materials. The main exclusions are design charges, planning costs and fees. We haven't included VAT, overheads and profit. Self build projects qualify for zero-rated VAT on labour and materials.