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Surplus Insulation & Plasterboard

Surplus PIR, EPS, mineral wool and plasterboard from UK contractors and merchants. Offcuts perfect for stud walls, full boards for first-fix — at trade-clearance prices.

Insulation is the fastest-moving surplus category on SurplusBuilder — every over-ordered PIR sheet, damaged Rockwool bat and end-of-line EPS pallet ends up somewhere, and most now flow through the marketplace instead of a skip. A full 1200×2400 Celotex GA4000 100mm board that retails at £48 sells surplus at £18–£26. Multiply across a stud wall or loft conversion and the saving pays for the rest of the build.

Surplus stock is factory-fresh — same lambda value (0.022 W/mK for PIR, 0.037 for Rockwool RWA45), same BBA certification, same fire rating. The only difference is that it was over-ordered on a new-build site or is a corner-dinged retail return. Reject anything with delamination, water damage or a musty smell; everything else is identical to merchant supply.

Plasterboard rides the same pattern. British Gypsum, Knauf and Siniat produce first-quality stock that ships as over-orders every week; SurplusBuilder aggregates it at 50–70% below merchant retail on a fast-moving commodity.

  • cheap Celotex offcuts
  • leftover plasterboard sheets
  • surplus PIR boards
  • end-of-line rockwool
  • discounted Kingspan
  • surplus Kingspan Kooltherm
  • cheap Celotex GA4000
  • surplus fire-line plasterboard

2026 UK price bands

Live SurplusBuilder listings sampled Q1 2026. Regional variation ±10–20%.

ProductSurplus £/m² or /sheetMerchant new
PIR 100mm (Celotex/Kingspan)£8.90–£14 /m²£22–£28 /m²
PIR 50mm£5.10–£7.80 /m²£12–£16 /m²
EPS 100mm£3.80–£5.20 /m²£9.40–£12 /m²
Rockwool RWA45 50mm£4.50–£6.20 /m²£11–£14 /m²
Plasterboard 12.5mm standard£4.50–£7 /sheet£11–£15 /sheet
Fire-line plasterboard£8–£12 /sheet£18–£24 /sheet

Buyer's checklist

  • ✓Match the exact product code: 100mm PIR is not interchangeable across brands for U-value calculations.
  • ✓Check foil facing is intact — damaged foil reduces thermal performance by 5–15%.
  • ✓Store PIR flat, off the ground, out of direct sun. Yellowed boards lose ~10% R-value.
  • ✓Fire-line plasterboard is pink-faced. Standard grey is not a fire substitute.
  • ✓For loft insulation, mineral wool is safer than PIR (no combustion concern between ceiling and floor joists).
  • ✓Cut PIR offcuts sell at ~40% of full-sheet price by area — great for stud-bay infills at 400/600mm centres.

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Related categories

Reclaimed Timber & Sheet Materials

Reclaimed and surplus timber, OSB, plywood and MDF from UK sites. Offcuts, full lengths and sheet job lots — perfect for joinery, decking, formwork and self-builds.

Surplus Roofing Materials

Reclaimed slates, surplus concrete and clay tiles, ridge tiles, membranes and underlay. Match an existing roof or save on a new build with stock cleared from UK sites and merchants.

Frequently asked questions

Are PIR offcuts as good as full boards?+

Thermally identical. They just need more cutting, taping and joint-filling on site. Ideal for stud walls, small bays and one-off pattress installations — but for a large uniform area, full boards are quicker and give a better airtightness result.

Is surplus PIR the same spec as new?+

Yes — surplus is factory-fresh, just over-ordered on the last job. Same BBA certificate, same lambda value (0.022 W/mK), same fire rating. Reject anything with visible water damage, delamination or musty smell.

Can mineral wool get wet?+

Recovers fully if it dries within 48 hours. Prolonged saturation permanently reduces R-value and creates a mould risk — dispose of anything that's been wet for a week or more.

How long can PIR be stored?+

Indefinitely if kept in original wrapping, out of direct sun and off wet ground. UV degrades the foil facing over ~6 months of exposure and reduces performance.

Can I use surplus plasterboard on a fire-rated wall?+

Only if the board is genuine fire-line grade (pink face, marked FR on the edge). Standard grey plasterboard is not a fire substitute and cannot be used to meet Building Regs Part B compliance on escape routes or party walls.

How do I transport plasterboard safely?+

Flat on a pallet, kept dry, ideally covered. A Transit fits about 15 sheets flat; a Luton with tail-lift takes 40–60. Stand-up transport cracks the corners and destroys the paper facing.