Start With What You Take Out

Before you order a single bag of cement, look hard at what is already on site. Most renovation projects throw away material that could go straight back into the build — floorboards, roof timbers, brickwork, paving, broken concrete and hardcore from an old path. The greenest material is the one you never have to buy, transport or manufacture. A slow walk-round with a notebook before demolition starts regularly saves money as well as carbon, because every tonne you keep out of a skip is a tonne you are not paying to tip.

Sort as you strip out. Keep clean timber, bricks, metal and hardcore separate, because mixed skips cost more to tip and are far less likely to be recycled properly. Remember your duty of care: waste leaving site should go with a licensed carrier and a waste transfer note, and if you plan to reuse excavated material on site you may need to register a waste exemption first. It is a short form, but do it before the grab lorry arrives.

Reclaimed Timber: Lovely, but Grade It Before You Trust It

Reclaimed timber is one of the best-value sustainable choices in the UK, and old-growth softwood and hardwood are usually denser and more stable than modern equivalents. Scaffold boards make excellent shelving, planters and non-structural studwork. Old floorboards, joists and roof rafters are superb for flooring, cladding, staircases and feature beams.

Two practical cautions. First, reclaimed timber is generally not accepted for structural use unless it has been strength-graded — visually graded to BS 4978 for softwood or BS 5756 for hardwood by someone qualified to do it. Your building control officer will want to see that. Second, check for nails, lead paint, woodworm and damp. A cheap moisture meter is worth buying; aim for under 20% before installing anything internally, or you will be sanding and painting around shrinkage cracks for a year.

Good sources include architectural salvage yards, reclamation auctions, demolition contractors and crate or pallet timber from local businesses. Ask where it came from and what it was previously treated with — old creosote and engine oil do not belong in a bedroom.

Recycled Aggregates and Hardcore: The Quiet Win

Aggregates are heavy, which means transport makes up a huge slice of their environmental impact. Crushed concrete, brick rubble, asphalt planings and quarry spoil are widely available and perfectly suitable for sub-bases, driveways, patio foundations, backfill and drainage surrounds.

• Type 1 sub-base made from crushed concrete performs well under paths, driveways and shed bases when compacted in layers of about 100mm.
• Crushed brick and concrete work as backfill to retaining walls and as general fill, provided drainage is considered.
• Do not use recycled aggregate in structural concrete unless it is certified to the relevant aggregate standard — your concrete supplier or engineer will advise.
• Hiring a mini crusher for a few days is often cheaper than skip hire and deliveries if you have more than a lorry load of hardcore to deal with.

Watch frost susceptibility in clay-heavy material, and keep an eye on how much fine dust is in the mix, as too many fines stop it draining.

Low-Carbon Insulation: Thicker, Softer, Usually Better for Old Walls

Insulation is where the biggest long-term savings live, and where material choice matters most. Rigid foam boards have high embodied carbon thanks to their blowing agents, while wood fibre, sheep's wool, hemp, cellulose (recycled newspaper) and recycled glass mineral wool all carry far less. Many are vapour-open, meaning they let moisture pass through rather than trapping it.

That matters enormously in older UK housing. If you internally insulate a solid brick wall with a sealed, impermeable layer, you risk pushing the dew point into the masonry and creating damp and rot. A breathable system used with a lime-based finish is usually the safer route, ideally backed by a hygrothermal assessment on a period property.

Be realistic about thickness. Natural insulants often have a slightly higher thermal conductivity than PIR, so you will need more depth to hit the same U-value — typically around 0.30 W/m²K for a renovated wall under Part L. Losing 50mm of floor space is usually a fair trade.

Small Swaps That Add Up

• Lime mortar for repointing older solid walls instead of cement, which traps moisture and can spall soft bricks.
• Concrete with GGBS or limestone fines replacing 30–70% of the cement — good carbon savings, though it cures more slowly in cold weather.
• Certified timber from responsibly managed forests, and homegrown larch or spruce where appearance allows.
• Reclaimed bricks for garden walls and non-exposed work, checking frost resistance before using them externally.
• Recycled plastic drainage and reclaimed slates, which are often cheaper than new and last decades.

Making It Work on a Real Project

Reclaimed is not automatically cheaper — salvaged bricks, floorboards and slates can cost more than new. The savings come from planning. Work out quantities properly, buy in one go, and have somewhere dry to store it. Allow extra lead time for salvage sourcing, and build a little contingency for waste and breakages, often 10–15% on reclaimed stock.

Talk to your building control officer early if you are using reclaimed structural timber, recycled aggregate or unfamiliar insulation, so there are no surprises at inspection stage. Keep a folder of receipts, grading certificates and waste notes. Then take photographs as you go — it is genuinely satisfying to look back at a finished room and know that half of it was already there before you started.