Can glulam be painted?

Yes — clear lacquer preserving timber grain (most common — Osmo PolyX, Rubio Monocoat), white lime wash, or opaque paint (acceptable but defeats aesthetic purpose). Lime wash + clear oil maintain breathability; opaque acrylic paint locks moisture potentially long-term.

Does glulam need fire protection?

Building Regs Approved Document B requires 30-min FR for structural members in single-dwelling (typical loft conversion). Glulam achieves this via 'sacrificial char' calculation — outer charred layer protects inner — typically 25–35mm sacrificial timber thickness, which means designed beam upsized 50–70mm beyond structural minimum. Engineer calculates. No paint required if char-design route used.

Does glulam shrink/move?

Less than solid sawn timber — kiln-dried + laminated grain orientation stabilises. Some movement still inevitable (1–3mm over 5m span seasonally). Allow for in joinery + ceiling junctions — small expansion gap with shadow gap or movement bead. Most clients don't notice.

Glulam vs Steel London Extension 2026 | Builderr

Glulam Beam vs Steel — Which Is Better for a London Extension?

Glulam (glued-laminated structural timber) vs steel for London extensions: glulam offers warmer aesthetic exposed beam + 80% lower embodied carbon (90 vs 1,540 kgCO2e/m³); steel offers slimmer profile + cheaper supply + longer spans. Glulam £450–£950/m supplied for typical 200×400mm beam; steel £85–£185/m supplied for equivalent 305×165 UB. Pick glulam where beam visible + extension is timber-aesthetic-led; steel where hidden, longer span (>6m), or budget-constrained.

When glulam wins

Aesthetic: exposed structural beam visible in finished room — glulam is a feature, steel is industrial (some clients want industrial; many don't). Warm timber finish matches Scandinavian/Japandi/biophilic design schemes. Embodied carbon: glulam ~90 kgCO2e/m³ vs structural steel ~1,540 kgCO2e/m³ — 17× lower. WLCA-conscious projects + RIBA 2030 Climate Challenge submissions favour glulam. Sustainability narrative for client + planning support. Spans: glulam handles 4–8m spans efficiently; over 8m steel pulls ahead on slenderness. Connections: bolted steel plate connectors (Simpson Strong-Tie SBE, Heco connectors) hidden inside beam — clean joinery look. Build-up: glulam single member often replaces composite steel-flitch-timber beams used in earlier loft conversions — simpler + tidier.

When steel wins

Span: 6–12m+ open-plan removal of internal walls — steel UB sections 305×165 or 406×178 efficient at depth/span ratio glulam can't match without becoming very deep. Compact section: where ceiling/floor depth restricted (e.g. retaining headroom in loft conversion, matching existing floor zone in extension at adjacent room) — steel slimmer, particularly PFC (parallel flange channel) at edges. Concentrated loads: steel handles point loads from columns above + cantilevers better than glulam. Cost: steel typically 40–60% cheaper supplied + installed than glulam for equivalent span/load — significant on tight budgets. Fire resistance: 30/60-min fire rating via intumescent paint or boxed boarding both possible — steel slightly faster + cheaper to box. Site availability: steel widely stocked, 1–3 weeks lead; glulam 4–10 weeks from German/Austrian/UK mills.

Cost comparison + sourcing

Glulam typical 200×400mm GL28h: £450–£950/m supplied including transport from mill (UK suppliers: Constructional Timber, Buckland Timber, Glulam Solutions; European: Hess Timber, KLH UK office). Engineer detail required (Eurocode 5 design). Connection ironmongery £45–£185 each. Installation typically 1–2 days for small project, similar labour to steel. Steel UB 305×165×40 grade S275 typical extension beam: £85–£185/m supplied + erected including padstones + connections. Fabrication 1–3 weeks lead from local fabricator (Hadley Steel, Smith Group). Whole-package comparison on typical 4m open-plan beam: glulam £2,400–£4,500 supplied + installed; steel £450–£950. Glulam premium £1,950–£3,550 for aesthetic + embodied carbon benefit. Justify by client priority + WLCA targets.