Cork wall coating for exterior walls on sound render or old plaster

1. Materials & Tools

Gather everything before you begin

Purpose:

Get everything on site before you open a container. The toner pack goes into the whole bucket in one mix, so the colour is set once for the whole job.

Products:

• Decork Façade: an 18 kg bucket of neutral product plus its 2 kg toner pack. One bucket covers about 15 to 20 m² in two coats

• Diaseal Strong sealant for every joint, with a caulking gun

• Optional finish: BKK Eco for wet regions

Tools:

• Mixing bucket and a drill with a helical-tip mixer
• Stainless trowel with rounded corners, or a texture hopper gun with a compressor. Façade is applied by trowel or hopper gun only
• Hawk, for trowel work
• Scraper, stiff brush and a vacuum
• Damp cloth for the tools
• Painter's tape, masking plastic, drop sheets for sills, paths and planting
• Clean water and a measuring jug

Plan the Day:

• Apply between +5°C and +35°C, on a dry wall
• Allow 8 to 10 hours between coats at 23°C and 50% humidity. Plan two days for most walls
• One person covers about 80 to 110 m² a day by trowel or brush. A hopper gun covers more
• Finish each wall in one session, corner to corner

2. Prepare the Wall

Sound, dry and clean, with every joint sealed

Purpose:

The wall must be sound, dry and clean before anything goes on it. Loose material, dust, grease or damp under the coating shows through it or lifts it.

All Walls:

• Clean from the top down. Brush off dust and cobwebs, wash off grease, then vacuum
• Scrape off anything loose and brush out the dust
• Check for damp. A wall with moisture, staining or rising damp needs its water source fixed first; the priming step then routes it to WATstop
• Mask trim, sills, fixtures and the floor. The coating is textured and cannot be sanded back off a trim line
• Remove or tape off outlet covers, light fittings and signs

Existing plaster or render: remove loose, hollow or chalking material back to a firm edge. Painted plaster takes the tape test below.

Joints:

• Seal every joint with Diaseal Strong before any coating goes on: panel joints, expansion and control joints, insulation board joints and the gap around fixtures
• Cut the nozzle to the joint width, fill to just below the surface, tool it smooth and wipe the surround
• Give the sealant 24 hours before priming or coating

Painted Surfaces:

• Press painter's tape firmly onto the paint and pull it off sharply. If paint lifts, remove it. If it holds, prime over it
• Remove loose, peeling or flaking paint in any case

3. Prime for Your Substrate

The wall decides the primer

Purpose:

Each substrate takes its own primer, from the product sheets: Grip Primer on slick surfaces, D20 on dusty or thirsty surfaces, WATstop on damp or rough concrete, and no primer on sound plaster.

Sound plaster or render: no primer. Go to mixing. Rough, dusty plaster takes D20 first, and so does painted plaster that passed the tape test.

4. Mix the Coating

Whole toner pack, high-speed mix

Purpose:

The toner pack gives the colour. Mix the whole pack into the whole bucket, once, so every wall gets the same colour.

Method:

• Empty the bag into the mixing bucket. Break up any lumps with the paddle
• Add the whole toner pack. Scrape the pack out
• Mix with a drill and a helical-tip mixer at high speed for at least 2 to 3 minutes. Work the paddle to the bottom and around the sides
• Stop and check the sides and bottom for unmixed product. Mix again briefly
• Add nothing but the toner and, where the method calls for it, clean water

Dilution:

• Façade: undiluted as a rule. In extreme heat, up to 5% water (0.9 L per 18 kg) and no more
• Add the water with a measuring jug. Mix it in fully before judging the consistency

Before You Apply:

• Mix a full bucket per batch. Plan batches to whole walls
• Brush a test patch on the primed wall and let it dry. The dry colour is the true colour; the wet mix looks darker
• Keep the lid on between loads so the surface does not skin

5. Apply Two Coats

Thin, even coats, one wall at a time

Purpose:

Apply two coats. The first coat covers and grips. The second coat closes the texture and evens the colour.

• Façade: stainless trowel or texture hopper gun only. 0.9 to 1.2 kg/m² over the two coats, about 2 mm when finished

By Trowel:

• Load a little material on the leading edge of the trowel from the hawk
• Lay it on at about 45°, then flatten the blade to spread it thin and even
• Work from the bottom up, never top down as material will easily fall off the trowel
• Use short strokes in changing directions, each overlapping the last. The cork grain fills the strokes
• Keep the coat thin. A heavy coat sags, dries slowly and goes white where it pools
• Keep a wet edge. Finish each wall corner to corner

By Hopper Gun:

• Fill the hopper. Set the compressor to at least 5 bar with a 3 to 4 mm nozzle
• Spray at a steady distance in overlapping passes. Keep the gun moving; a pause leaves a heavy patch
• Mask wider than the wall. Overspray carries

Second Coat:

• Apply the second coat after the first has dried fully, about 8 to 10 hours at 23°C and 50% humidity, longer in cold or damp weather
• Same method, same thickness, bottom up
• Check the first coat in raking light before you start. Cover thin spots and misses with the second coat

Conditions:

• Apply between +5°C and +35°C on a dry wall
• Vertical surfaces only. Standing water turns the finish white, so shape sills and ledges to shed water
• Outside, keep direct sun, wind, rain and frost off the wall during application and the first hours of drying

6. Drying & Protection

Calm conditions while it cures

Purpose:

The finish dries in about 10 hours at 23°C and 50% humidity. The first 2 hours matter most: rain, frost, direct sun or wind in that window mark the coat.

Drying:

• About 10 hours at 23°C and 50% humidity. Cold and damp stretch every drying time
• A heavy coat takes much longer to dry. Keep coats thin
• Protect from rain, frost, direct sun and wind for at least the first 2 hours
• Indoors, ventilate the room and keep it at room temperature. Keep heaters off the wall

Finishing Up:

• Pull the masking tape once the surface is dry to the touch. Draw it away at a low angle so the edge stays clean
• Wash tools with water before the coating dries on them
• Keep hands, furniture and bags off the wall for the first day

7. Optional Protection

For high-traffic and wet-region walls

Purpose:

Most walls are finished at the previous step. Two situations call for a sealer.

• Exterior walls in wet regions: BKK Eco adds water repellency. Apply it per its own sheet, over the fully dried finish

Most walls need no sealer.