ACTFLEX 400 CLEAR Clear waterproofing membrane
Clear temporary leak repair solution for tiled balconies and bathrooms
Fix a leaking balcony or shower without removing a tile. Three thin clear coats, no primer.
How ACTFLEX 400 CLEAR goes on
ACTFLEX 400 CLEAR coverage, coats and cure times
A clear, semi-gloss membrane that goes over the existing tiles and grout and fixes the leak for up to five years. It is a temporary membrane, not a permanent waterproofing system.
- Coverage
- ≈ 3 m²typicalper 1 kg over tiles (3 kg ≈ 9 m², 7 kg ≈ 21 m²) · TDS p2
- Coats
- 3thin, even coats, no primer · TDS p2
- Dry film
- 0.2 mmover tiles; 0.5 mm over grout, joins and concrete · TDS p2
- Recoat
- 4 hminimum; all coats within 48 hours · TDS p2
- Keep dry
- 3–5 daysno rain or water after the final coat · TDS p4
- Full cure
- 5–7 daysafter the final coat · TDS p2
- Leak fixed
- Up to 5 yearstypicalon a clean, sound, prepared surface · TDS p2
- Pack
- 1, 3, 7 kgsingle pack: trowel, brush or roller · TDS p1
- Apply at
- 10°C minsurface temperature; moisture below 4% · TDS p2
From the FORSPEC data sheet, TDS-400CLEAR · Revision 2 · 12 August 2026. Times are at 25°C and 50% relative humidity unless the data sheet says otherwise. Typical = FORSPEC’s own typical value, not a laboratory-certified one.
Where ACTFLEX 400 CLEAR is used
Use it for
- Leaking tiled balconies, courtyards and terraces
- Leaking tiled showers and internal wet areas
- Parapet walls, hobs and building exteriors
- Terracotta tiles and pavers
- Sandstone and face brick walls
- Top-coating and sealing timber floors
Know before you start
- A temporary membrane: it fixes the leak for up to 5 years and is not a permanent fix. No product warranty is offered.
- Does not fix broken, popping or loose tiles or loose grout: repair them first
- Never on a damp surface or over water trapped under the tiles
- Not slip-resistant as supplied: broadcast ACTFLEX ANTISLIP into the second coat
Its FORSPEC systems
How to apply ACTFLEX 400 CLEAR
- 01
Repair
Replace broken, popping or loose tiles. Rake out loose grout and replace it. Repair every crack with ACTFLEX MS PRO before coating.
- 02
Clean and dry
Remove dust, grease, moss and mould. The surface must be dry, below 4% moisture, with no rain or water on it for 3 to 5 days first.
- 03
Fill corners
Fill and fillet every corner, wall and floor junction, hob junction and penetration with ACTFLEX MS PRO, tooled smooth and cured tack-free.
- 04
Mix
Stir well. By trowel, use it neat to fill grout lines. By brush or roller, dilute 2 parts product to 1 part clean water, for example 1 kg with 0.5 L.
- 05
Apply
Three thin coats, the first with a mohair roller. At least 4 hours between coats and all coats within 48 hours. For grip, broadcast ACTFLEX ANTISLIP into the wet second coat.
- 06
Cure
No rain, washing or sitting water for at least 3 to 5 days after the final coat. Full cure takes 5 to 7 days. Foot traffic once cured.
A short guide from the data sheet. Read the full ACTFLEX 400 CLEAR TDS before you start.
How much ACTFLEX 400 CLEAR do I need?
Clear membrane over tiles, 1, 3 and 7 kg
Over tiles, diluted 2 : 1, three thin coats: 1 kg covers about 3 m², 3 kg about 9 m², 7 kg about 21 m². Grout lines, mortar and concrete build to 0.5 mm and use about 0.9 to 1.1 kg per m². Best mix is the least product that covers the job in the fewest pails.
You need
0 pails
Where the figures come from
Over tiles, diluted 2 : 1, three thin coats: 1 kg covers about 3 m², 3 kg about 9 m², 7 kg about 21 m². Grout lines, mortar and concrete build to 0.5 mm and use about 0.9 to 1.1 kg per m². Best mix is the least product that covers the job in the fewest pails.
- Practical yield over tiles, 3 thin coats: 1 kg about 3 m²; 3 kg about 9 m²; 7 kg about 21 m². TDS-400CLEAR, R2, 12 Aug 2026, page 2
- Joins, grout, mortar, level surfaces, 0.5 mm: about 0.9 to 1.1 kg/m² (1.0 used). TDS-400CLEAR, R2, 12 Aug 2026, page 2
ACTFLEX 400 CLEAR questions
Do I have to remove the tiles?
No. ACTFLEX 400 CLEAR goes over the existing tiles and grout. Broken, popping or loose tiles and loose grout must be fixed first, because it relies on the surface it covers.
Is ACTFLEX 400 CLEAR a permanent waterproofing membrane?
No. It is a temporary clear membrane that fixes the leak for up to five years on a sound, prepared surface. When a permanent fix is wanted, the tiled system is replaced with a FORSPEC membrane system.
How much do I need?
As a guide, 1 kg covers about 3 m² in three thin coats over tiles when diluted 2 to 1 with water. A 3 kg pack covers about 9 m² and a 7 kg pack about 21 m². Rough grout and porous surfaces use more.
Can I walk on it?
Yes, once it has cured. It is not slip-resistant as supplied. For grip, broadcast ACTFLEX ANTISLIP into the wet second coat and lock it in with the third.
Will it change the look of my tiles?
It dries clear with a semi-gloss finish. It can turn cloudy white where water ponds and clears again as the water dries. Some yellowing may occur over its service life.
Can I apply it to a damp balcony?
No. The surface must be completely dry, below 4% moisture. If water is trapped under the tiles, let it air for at least 3 to 5 days and confirm it is dry first.
Used with ACTFLEX 400 CLEAR
ACTFLEX 400 CLEAR TDS and SDS
Always work from the current data sheet. Every FORSPEC TDS and SDS →
Specify it. Or buy it.
Send the drawings or photos and FORSPEC comes back with the system, the details and the quantities. Or find a FORSPEC stockist for ACTFLEX 400 CLEAR.