Bungaroosh Pitfalls in Garage Conversions – Brighton & Hove Edition

Why flint-and-lime walls demand specialist care before you swap that garage door for bi-fold glass.

What Makes Bungaroosh Different

Bungaroosh isn’t brick: it’s a loose cocktail of beach flint, broken brick, chalk nodules and lime mortar. Those voids and soft aggregates mean:

  • High capillary action—walls suck up water fast, then dry unevenly.

  • Low compressive strength—new point loads can crush internal pockets.

  • Salt content—sea-spray chlorides migrate and crystallise behind dense coatings.

Ignoring these traits is the fastest route to cracks, bulging render and persistent damp after a garage conversion.

Common Mistakes Contractors Make

Covering walls with cement render

  • Cement locks in moisture and pushes salts outward. Bulges appear within two winters.

Injecting chemical DPCs

  • Fluids can’t spread evenly through voided bungaroosh; you get patchy damp lines instead.

Fixing goal-post frames with rawlplugs

  • Lime mortar crumbles around expanding fixings. Resin anchors or through-bolts into sound brick pockets are safer.

Using gypsum plaster

  • Gypsum sets fast but dries the lime matrix, leading to surface dusting and hairline cracking.

Skipping salt-draw cycles

  • New finishes detach when trapped chlorides expand. Clay poultice draws salts out before plastering or rendering.

Essential Prep Steps for a Healthy Conversion

  • Strip any cement render or waterproof paint back to bare lime.

  • Run moisture readings (capacitance meter) every metre; mark damp hotspots.

  • Apply clay-and-paper poultice; repeat until salt bloom fades.

  • Pin deep voids with chestnut laths and hot-lime mortar for structural continuity.

  • Embed stainless mesh across wall-to-steel junctions to absorb differential movement.

Breathable Build-Up That Works

Internal option

  • 25 mm hot-lime base coat

  • 40 mm wood-fibre insulation board bedded in lime

  • 5 mm fine lime skim and mineral paint finish

External option

  • Three-coat lime render at 18 mm total thickness

  • Silicate paint for colour and extra weather protection

Either build-up avoids condensation, lets salts escape and hits modern U-value targets once paired with roof and floor insulation.

Thermal Bridge Alerts

  • Steel goal-post legs sitting on a cold slab—wrap legs in 10 mm aerogel or fit thermal break shoes.

  • Window reveals where wall thins—return insulation 20 mm onto the frame and seal with airtight tape.

  • Junction between dwarf brick infill and bungaroosh—slip a strip of mineral-wool cavity closer to cut cold conduction.

Ventilation Rules for Lime-Rich Walls

  • Fit humidity-tracking extract fans or MVHR; bungaroosh loves fresh airflow.

  • Locate vent terminals away from prevailing south-westerlies to reduce salt spray ingestion.

  • Specify ducting with smooth rigid pipe; flexi hose traps condensation.

Signs Your Contractor Understands Bungaroosh

  • Mentions hot-lime, not sand-cement.

  • Talks about salt-draw or poulticing before plastering.

  • Specifies breathable insulation such as wood-fibre or mineral-wool.

  • Proposes stainless fixings and resin anchors, not plastic plugs.

  • Provides a moisture-monitoring schedule post-completion.

After-Care Checklist

  • Limewash or silicate coat every five to seven years.

  • Keep gutters clear; bungaroosh walls drink overflowing rainwater fast.

  • Hose down facade with fresh water each spring to rinse surface salts.

  • Refill hairline cracks (<1 mm) with lime putty as they appear.

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