Guide

How much stone do I need? Estimating tonnage for a dry stone wall rebuild

The working rule for a UK dry stone wall is one tonne of stone per square metre of wall face. That covers face stone, hearting, throughs and copes — everything that ends up in the finished wall. Most experienced wallers use a slightly bigger number for the order, around 1.1 to 1.2 tonnes per square metre, to allow for breakage, mis-fit and the inevitable lumps that look right at the quarry but go straight on the hearting pile when you actually start laying.

The rest is detail. Here is the detail.

What "a square metre" means

A square metre of wall face is one metre of horizontal length by one metre of height. A wall 10 metres long and 1.2 metres high is 12 square metres of face.

For a double-faced wall (the standard field boundary), each square metre of face implies stone on both faces plus hearting between them. The 1 tonne/m² rule is calibrated for this — it is the figure most quarries and stone merchants will agree on for a standard 0.5m to 0.6m wide wall.

For a single-skin wall (garden, decorative, retaining-against-bank), the per-square-metre figure drops to roughly 0.5 to 0.7 tonnes/m², because you only have one face plus a smaller backing. Confirm with the supplier — single-skin orders are easier to get wrong.

For a wider-than-standard wall (some boundary walls in the Dales run 0.8m wide at the base), scale up proportionally. A wall 0.75m wide at the base needs roughly 25 per cent more stone than the standard 0.6m wall.

A worked example

A 20-metre rebuild of a standard double-faced field wall, 1.2m high:

• Face area = 20m × 1.2m = 24 square metres.
• Stone required at 1.1 tonnes/m² = 26.4 tonnes.
• If 70 per cent is reclaimable on site, the buy-in is 8 tonnes.

That is the order. Most wallers round up to the next half-tonne for a delivery — so order 8.5 tonnes and let the extra sit at the side. You will use it for pinning, hearting, or the small bit of wall the customer asks you to "just tidy while you are here".

Reclaim ratio — the hardest part of the estimate

Reclaim ratio is the proportion of the existing wall stone that is sound enough to go back in. The honest range across UK field-boundary work is 60 to 90 per cent. Below 60 per cent and you are essentially building a new wall with old stone — flag it on the quote as a major buy-in. Above 90 per cent and you are essentially sorting and re-laying — the customer should benefit on the price.

Walk the wall before you quote. Look for:

• Frost-shattered stone (white powder on the bed faces, splits along the natural grain).
• Stone that is too small for anything but hearting.
• Buried stone in the field — count it as half-recoverable unless you can see it.
• Missing throughs — these are the heavy 0.6m+ stones that bond the two faces. If they are gone, you are buying them in.

A safe quote padding: estimate the reclaim ratio, then knock 10 per cent off it before ordering. If your eye says 80 per cent, order for 70 per cent. The over-order goes back next time.

Where to source replacement stone

• Local quarries. Best quality match for the regional stone type. Yorkshire gritstone, Cotswold limestone, Welsh slate — go local. Expect £80 to £160 per tonne delivered, depending on distance and stone type. Cotswold dry-stone-grade limestone runs higher; sometimes £180 to £220 per tonne.
• Reclamation yards. Honest reclaimed stone, weathered to match. Pricier than fresh quarried (£140 to £240 per tonne) but invisible alongside old stone. Worth it on heritage and conservation work.
• Farm yards. Pile of stone in the corner of someone else's farm, sold by the load. Cheap, variable quality, brilliant if you know the farmer.

Always order in delivered tonnes and confirm the truck can reach the site. A 16-tonne wagon that cannot get past the gate is a day lost and a stack of stone in the wrong field.

The wall types and their nuances

• Field boundary, double-faced — the 1.0 to 1.1 tonnes/m² rule applies cleanly.
• Garden wall, double-faced — same rule, but more pinning stone wanted for the finer faces.
• Retaining wall — single face, heavy backing. Treat as 0.6 to 0.8 tonnes/m² of face but add 0.3 to 0.5 tonnes/m² of backfill stone behind.
• Feature / heritage walls — order 15 per cent over because cut-stone wastage is higher.

FastQuote prompts for the wall dimensions on the quote, so the tonnage line on the document is consistent with what you have measured and not a number you have to remember to update.

Related: Cost per metre · What's in a quote