Everbuild404 Fast Powerful Fungicidal Wash – Removes Lichens, Fungi and Algae – Exterior and Interior use – 1 litre

From the outset, I approached Everbuild 404 as a rigorous, multi-stage mould remediation solution rather than a casual cleaner. This wasn't about a light spritz and forget—it was about reversing embedded biological infestation across a combination of interior plaster, exterior render, and biological algal ingress on uPVC. What sets Everbuild 404 apart is not merely its advertised performance, but its real-world efficacy when applied with strategic precision, adjusted exposure time, and surface-specific methodology. Across six weeks of testing, I trialled this on 11 distinctly different materials—from porous lime plaster to gloss skirting boards, bath sealant, cement board, garden flags, and timber soffits—all under varied humidity, age of infestation, and sunlight exposure.The real game-changer is in its uncut, ready-to-use formulation. Unlike concentrate products, Everbuild 404 demands no dilution, which eliminates user error during prep. This purity translates into a potent impact, particularly where the infestation is layered deep into breathable surfaces like internal plasterboard. In those cases, simply misting is insufficient. What worked instead was a three-phase strategy: brush agitation, then saturation soak, then reapplication after 12 hours. Using a soft bristle brush (not too coarse, to avoid driving spores deeper), I’d gently loosen surface layers before flooding the zone with spray. In two of the cases, the initial signs of black mould faded in under 30 minutes, but it was after 24 hours that the deep fungal colonisation showed visible regression.One heavily affected Victorian wall corner, which had recurring black and green mould due to condensation and external bridging, responded best to a high-volume dabbing method with a foam pad saturated in Everbuild 404. This allowed better soaking into the internal plaster matrix. I covered the area with plastic sheeting after application to slow down evaporation—thus extending surface contact time. Result: complete visible mould reversal without reappearance even four weeks later under the same RH conditions (~78%).For deep-seated infestations in cracked plaster or cavities (where musty odour often suggests biofilm activity beneath paint), I trialled two approaches. First, direct injection via a disposable syringe into visible micro-cracks—this worked surprisingly well in driving fungicide into otherwise inaccessible substrate. Second, a sponge-over method where I pressed the solution into the plaster and sealed it under cling film. After 48 hours, the smell was neutralised, and there were no surface stains.Exteriorly, I had long-standing issues with algae bloom on north-facing painted render and lichens on a tiled roof valley. Application via pump sprayer on a dry, windless day yielded best results. Key insight: apply only during low sun to prevent premature evaporation. The render, once saturated and left for an hour, showed streaks of dead green algae within hours, and full clarity within 48 hours post-wash. Lichens required brush agitation first; their waxy coating otherwise resists penetration.Now, safety isn’t an afterthought with this product—it’s an imperative. Everbuild 404 contains potent biocidal agents. You must wear nitrile gloves (avoid vinyl, as some compounds diffuse through), long sleeves, and eye protection. I used a 3M P3-rated mask during interior application, especially when brushing, to avoid airborne spore inhalation. Ventilation is critical indoors—leave windows open, block HVAC vents, and isolate treated rooms.The product’s performance differs on gloss vs. matt vs. raw materials. On silicone grout lines and gloss bathroom sealant, I found the solution alone sufficient with no agitation. Spray, wait 20–30 minutes, rinse with warm water—done. On raw painted MDF or old emulsion walls, brushing was essential. Interestingly, on smooth satin paint, results were patchy unless lightly sanded first.Storage and repeat usage are also practical. I decanted part of the bottle into a glass spray bottle for spot treatments and left the main container sealed. Even after four weeks, the strength remained unchanged. There’s a subtle chemical smell upon spraying (expected with any fungicide), but it dissipates quickly and doesn’t cling to fabrics or wood.One advanced tip I discovered: for deeply stained areas, pre-wet surrounding dry plaster to prevent overabsorption from adjacent dry zones. This ensures the solution remains active where it’s needed most, not wicked away.Perhaps the most impressive result came from a secondary bathroom ventilation issue. A corner had visible brown spore clusters, including early-stage mycelium spread under a sealed paint layer. After sanding back the paint, I doused the area liberally, left it overnight, then applied two further coats over two days. Post-treatment humidity testing showed no regrowth, and odour sensors read clean. That zone has since stayed clear, without the need for anti-mould paint—testament to the product’s residual barrier effect.Cost savings? Immense. Contractors had quoted upwards of £380 for whole-wall antifungal treatment. Instead, I tackled it myself with two £6.35 bottles, a quality brush, mask, gloves, and about four hours of my time. The value is not just monetary—it’s in the peace of mind that what’s lurking behind that wall or beneath the sealant is finally, chemically neutralised.Crucially, Everbuild 404 doesn’t bleach—this is not a cosmetic wipe—it kills at the microbial root. I confirmed this by re-testing areas with ATP surface swabs post-treatment. On untreated patches, the swabs lit up; on Everbuild-treated areas, levels were negligible, suggesting actual biological death rather than surface displacement.his product excels when used with thought, attention, and patience. If you go in expecting a one-minute miracle spray, you’ll be disappointed. But if you approach it like a microbial remediation process—with layers, contact time, and mechanical support—it rewards you with clinical results.In closing, I now use Everbuild 404 not just for emergencies, but proactively in seasonal mould-prone areas. It’s now part of our winter prep: bathroom corners, north walls, and garden brick bases get annual treatment to stave off bloom. For its cost, coverage (~5–10 m² per litre), residual effect, and compatibility across materials, I consider it one of the best-value fungicidal solutions available in the domestic sector.Everyone with an old home, poor ventilation, or a damp-prone zone should have this. And wear your gloves—it’s strong because it needs to be.

A good quality product. Easy to use. Does the job.

It does what it claims!

Got it to clean growing patches of green mildew on an external cellar light well (painted white). Just sprayed a load on and left it for a while and the brickwork cleaned up. To be honest I didn't wipe or rinse it off. Has kept the mildew away since.Good product.

The item was absolutely filthy and almost a year out of date!!

Works OK. Bottle is faulty so only has a direct spray option, the mist does not work

Used this to clean my stone windowsills outside and brought them up great!! Only problem was the trigger which was pretty poor. Ended up having to pull the trigger out with one finger before squeezing it again with my other fingers.So maybe have another spray bottle on hand. I only had 3 sills to do so struggled on.

Have been getting black mould due to poor ventilation in my flat and radiator being directly under the window. Previously tried a more natural remedy of vinegar solution to clear it but the mould returned.This, so far at least, has kept it at bay