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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