Blown Render on Your Home? We'll Strip It Back and Rebuild It in Wolverhampton

Render is said to be 'blown' when it has lost its bond to the wall behind: tap it and it sounds hollow and drummy instead of solid. Left alone, blown areas crack along their edges, admit water, and eventually drop off in sheets. Because the failure is invisible until it's tapped, blown render is usually bigger than it looks — which is why a proper survey comes before any repair. Here is how it happens and how we deal with it.

Why render blows

Render loses its grip when water or poor application breaks the bond. Water is the main driver: it enters through cracks, porous patches, failed sills or a leaking gutter, saturates the wall-render interface, and frost then expands it and levers the render away a little more each winter. Salts dissolved in that moisture crystallise behind the render surface and push it off the wall. Poor application does the same job more quickly: render applied over dust, dried-out or very absorbent backgrounds without a bonding treatment, or applied too thickly in one pass, never forms a proper mechanical and chemical bond.

The consequence worth understanding is that blown render is a water trap — the hollow space collects moisture, which accelerates the failure and keeps the wall behind damp. That damp shows indoors as stains long before the render falls.

How we survey and map it

We sound the entire affected elevation with a hammer or tapping bar, marking the boundary between solid and hollow render — the honest extent is usually a good deal larger than the visible cracks suggest. We open a small area where needed to inspect the wall behind: is it saturated, salt-contaminated, crumbling, or sound? We trace the water: gutters, downpipes, sills, seals, copings, ground levels and drainage. And we identify the background — brick, block, old render — and the render type, because the repair specification depends on both.

The repair itself

Hollow render comes off — there is no honest way to re-bond it in place. We cut back to a clean square edge in sound material, strip the failed area, and prepare the background: treating absorbent surfaces with a bonding coat or spatterdash so new render keys properly, and allowing saturated walls to dry or drying them as the schedule allows. New render goes on in layers to the correct thickness for the background, with a finish matched to the rest of the elevation.

Where hollow patches are small, few and caused locally, spot repair is proportionate. Where they are widespread, or the render is old and failing generally, patching becomes an endless cycle and a full re-render of the elevation is the honest recommendation — quoted as a project after survey and staged over several dry working days. Either way, the cause — dripping downpipe, cracked sill, failed coping — is repaired first, or the new render follows the old one off.

Weather, timing and expectations

Render needs dry walls and frost-free curing, so work is scheduled around conditions and we will tell you plainly if the forecast must move your dates. Patched repairs are matched as closely as materials allow, though new render beside weathered old render can look slightly different — re-finishing the whole elevation is the route to uniformity if that matters to you. We cannot guarantee against future cracking, particularly where the building moves seasonally, but a properly bonded render with its water source controlled gives the wall its best working life.

Aftercare

Keep gutters and downpipes clear and sound. Inspect joints and render each spring and seal hairline cracks before winter opens them. Avoid pressure washing repaired walls.

Booking your survey

Book through maintenance-men.com or by phone. You pay a booking fee when you book, and labour is charged hourly at a rate that depends on how soon you need the visit. The full cost of the agreed work is quoted and approved before we start, with parts and materials quoted separately. Send photos of the affected wall when you book — they help us plan the survey.