Every renovation and extension rests on the same handful of structural material decisions: what the walls are built from, what holds the floors up, what spans the openings, and what the whole thing sits on. In 2026, UK structural materials range from £8–£14/m² for a sand-cement floor screed to £310–£420/m³ for C24 structural timber and £95–£130/m³ for ready-mix concrete — and specifying the wrong grade or type costs far more to correct later than it does to get right the first time.
This guide brings together our structural materials library in one place — bricks, blocks and mortar, concrete and foundations, steel, structural timber, and floors and screeds — so you can see how the pieces fit together before you order anything or brief a contractor.
Bricks, Blocks & Mortar
Brick choice sets both the look and the durability of a wall. Our guide to types of brick explains why a soft common brick used below DPC will spall within a decade, while spalling brick repair cost covers what it costs to fix if that damage has already started. Before you order, check UK brick sizes and bonds so quantities and setting-out match the existing wall.
Behind the facing leaf, concrete blocks do most of the structural and thermal work in a modern cavity wall, held together across the cavity by cavity wall ties at a standard 900 × 450 mm spacing. Once the leaves are tied, the cavity itself usually gets filled — see cavity wall insulation for how full-fill, internal and external options compare on U-value and cost.
Both bricks and blocks are bedded and jointed in mortar, and the two materials behind it deserve equal care. Cement types explains why the wrong bag — rapid-set instead of sulfate-resisting, for instance — can cause premature failure below ground. For the mix itself, how to make mortar covers ratios and consistency for DIY batches, while mortar mix ratios sets out the full M2–M12 designation system for matching mix strength to application.
| Material | Typical Cost (2026) | Typical Use |
|---|---|---|
| Facing brick | £350–£900 per 1,000 | External walls, visible brickwork |
| Aircrete block | £1.20–£2.50 per block | Inner leaf, thermal blockwork |
| Ready-mix concrete (C25–C30) | £95–£130/m³ | Foundations, ground-bearing slabs |
| Structural steel (S275 UB) | £30–£150/m | Beams over openings, load transfer |
| C24 structural timber | £310–£420/m³ | Floor joists, roof members |
| Sand-cement floor screed | £8–£14/m² | Level bed over slab or insulation |
Figures are 2026 UK supply costs; add labour and, for steel, fabrication and delivery.
Concrete & Foundations
Concrete is specified by strength, not just quantity. Concrete grades explains what C20 to C40 actually mean and which grade suits a strip foundation versus a ground-bearing slab, and the foundation itself needs choosing before any concrete is ordered — foundation types compares strip, trench-fill and raft options on depth, volume and cost.
Underneath a slab or driveway, MOT Type 1 sub-base prevents settlement and bridging voids provided it is compacted correctly in layers, and every ground floor needs a continuous damp proof membrane linked to the wall’s DPC to keep rising moisture out. Where a slab or beam has to resist tension rather than just compression, rebar and mesh sizing sets out the B500B grades and A142–A393 fabric specifications Building Control will check on site.
Steel
When a wall comes down or an opening gets wider, something has to carry the load above it. Steel beam sizes explains the RSJ, UB and UC designations, and why a £200 beam can become a £1,500 installed item once fabrication and craneage are added. For smaller openings, a lintel does the same job at a fraction of the cost — steel, prestressed concrete and stone each suit different spans and finishes.
Wherever a beam lands on masonry, check the bearing: a padstone spreads the point load into the wall below so the blockwork doesn’t crush or crack under it.
[!tip] Get the engineer’s calculation before you order Never size a beam, lintel or padstone by eye or by “what the last job used.” A structural engineer’s calculation costs a few hundred pounds and confirms the exact section and bearing you need — undersizing is a safety issue, and oversizing wastes money on steel you didn’t need.
Structural Timber
Structural timber is strength-graded, and the two grades you’ll meet on almost every job are covered in C16 vs C24 — C24 costs more but handles longer joist spans and trussed rafters where C16 falls short. For longer clear spans without deepening the section, glulam and LVL engineered beams outperform solid timber on strength and dimensional stability.
Deciding on the structure itself rather than just its members? Timber frame vs masonry compares cost, build speed and thermal performance for a new build or large extension. Whichever frame you choose, the floor and roof members still need correct sizing — joist span tables sets out spans and spacing for solid timber and I-joists under Approved Document A.
Floors & Screeds
Ground floors come in three main forms, compared directly in beam and block vs concrete slab ground floors, alongside the suspended timber alternative covered in suspended timber floors — still common in Victorian and Edwardian houses and reliant on proper airbrick ventilation to avoid rot. Whichever structure you choose, floor insulation build-ups explain how PIR, EPS and mineral wool trade off thickness against U-value within a fixed floor depth.
On top of a solid floor, floor screed levels the surface and, increasingly, carries underfloor heating — sand-cement and liquid anhydrite dry at very different rates. On a timber deck instead, chipboard, OSB and plywood compares the three panel products on moisture resistance and stiffness, so a swollen floor doesn’t turn into a new-build defects claim.
Where to Start
If you’re building or repairing a wall, start with types of brick to get the specification right before you order. If you’re widening an opening or taking out a wall, read steel beam sizes alongside foundation types so both ends of the structural chain — what carries the load, and what it bears onto — are sorted together before work starts.
