F. Ball Stopgap F77 Epoxy Damp Proof Membrane
F. Ball Stopgap F77 Epoxy Damp Proof Membrane - 7kg is backordered and will ship as soon as it is back in stock.
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| Area | Excluded postcodes |
|---|---|
| North-east Scotland | AB31–AB45, AB51–AB56 |
| Central & northern Highlands | FK19–FK21; all IV |
| Outer Hebrides | All HS |
| Arran & Cumbrae | KA27–KA28 |
| Caithness, east Sutherland & Orkney | All KW |
| Argyll & Inner Hebrides | PA21–PA38, PA41–PA49, PA60–PA78 |
| Perthshire & western Highlands | PH1 1, PH1 3, PH1 4, PH5–PH10, PH15–PH26, PH30–PH44, PH49–PH50 |
| Shetland | All ZE |
| Northern Ireland | All BT |
| Channel Islands & Isle of Man | All GY, JE & IM |
| Isles of Scilly | TR21–TR25 |
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F. Ball Stopgap F77 is a professional, solvent-free, two-part epoxy resin system that cures to form a high-performance waterproof surface membrane. It impedes residual construction moisture and rising damp in suitable concrete and sand/cement screeds before smoothing compounds, adhesives and floor coverings are installed.
Applied as a single coat, F77 can be used at subfloor relative humidity readings of up to 98% RH. It cures from approximately three hours at 20°C, making it ideal for fast-track domestic and commercial flooring installations where waiting for the subfloor to dry naturally would cause unnecessary delays.
Stopgap F77 is supplied as a pre-measured resin and hardener kit and is available from WWFS in practical 7kg and 14kg sizes.
Key Benefits
- Professional two-part epoxy waterproof surface membrane.
- Impedes residual construction moisture and rising damp.
- Single-coat application at readings up to 98% RH.
- Suitable over correctly commissioned cementitious underfloor heating screeds up to 90% RH.
- Rapid curing from approximately three hours at 20°C.
- Black pigmentation helps installers visually check coverage.
- Suitable beneath compatible Stopgap smoothing compounds and flooring adhesives.
- Allows earlier installation of suitable floor coverings.
- Solvent-free formulation.
- Available in 7kg and 14kg kits.
Ideal For
- Prepared concrete subfloors.
- Prepared sand and cement screeds.
- New-build concrete containing residual construction moisture.
- Domestic renovation projects.
- Commercial and fast-track flooring installations.
- Correctly commissioned cementitious underfloor heating screeds.
- Projects receiving wood flooring, LVT, vinyl, carpet or another suitable floor covering.
Professional Advice
Always test and record the subfloor moisture level before choosing the application rate. Stopgap F77 must be applied to a clean, absorbent and slightly textured surface. Remove laitance, surface hardeners, adhesive contamination, oil, grease and anything else that could prevent adhesion. Power-floated concrete must be mechanically prepared.
The substrate should have a surface strength greater than 1.5N/mm². The cured membrane must form a continuous, glossy black coating without pinholes, weak areas or missed sections. Never exceed the specified coverage rate, as spreading the product too thinly may prevent it from providing the required moisture protection.
Coverage and Application Guide
Up to 85% RH
- Application rate: Approximately 2.5m² per kg.
- Trowel: STYCCOBOND A2 trowel.
- 7kg coverage: Approximately 17.5m².
- 14kg coverage: Approximately 35m².
Above 85% RH and Up to 98% RH
- Application rate: Approximately 1.8m² per kg.
- Trowel: 1.5mm × 5mm trowel supplied with the kit.
- 7kg coverage: Approximately 12.5m².
- 14kg coverage: Approximately 25m².
Underfloor Heating Screeds Up to 90% RH
- Application rate: Approximately 1.8m² per kg.
- Trowel: 1.5mm × 5mm trowel supplied with the kit.
- 7kg coverage: Approximately 12.5m².
- 14kg coverage: Approximately 25m².
One Coat – Different Application Weights
Stopgap F77 is a one-coat system at both application rates. Higher moisture readings require a heavier coat applied with the supplied 1.5mm × 5mm trowel, rather than two standard coats.
Immediately back-roll the applied epoxy with a pre-coated paint roller to flatten the ridges and create an even, continuous and pinhole-free membrane. Where a very absorbent surface leaves a subdued shine, or pinholes or weak areas remain, a second application will be required.
Technical Specifications
| Product Type | Solvent-free, two-part epoxy waterproof surface membrane |
|---|---|
| Available Sizes | 7kg and 14kg kits |
| Components | Pre-measured resin and hardener |
| Colour | Black |
| Maximum Moisture Reading | Up to 98% RH on suitable cementitious subfloors |
| Underfloor Heating | Up to 90% RH on correctly commissioned cementitious heated screeds at approximately 1.8m² per kg |
| Working Time | Approximately 30 minutes at 20°C once mixed and poured onto the floor |
| Curing Time | From approximately three hours at 20°C |
| Application | Specified notched trowel followed immediately by back-rolling |
| Suitable Substrates | Prepared, clean and absorbent concrete and sand/cement screeds |
| Minimum Substrate Strength | Greater than 1.5N/mm² |
| Indoor Use | Yes |
How to Apply Stopgap F77
1. Test the Subfloor Moisture
Use an appropriate calibrated hygrometer to establish and record the relative humidity of the subfloor. The reading determines the required application rate and coverage.
2. Prepare the Surface
Remove laitance, surface treatments, weak material and contamination to produce a clean, absorbent and slightly textured surface. Power-floated concrete must be mechanically prepared. New concrete and sand/cement screeds should normally be left for at least seven days before preparation and application.
3. Repair or Pre-Smooth Where Required
Rough, uneven or damaged cementitious subfloors must be repaired or pre-smoothed before applying F77. Suitable products can include Stopgap 1200 Pro or another compatible Stopgap product selected for the substrate and required depth.
Any smoothing compound installed beneath the membrane must be fully dry and sufficiently strong before F77 is applied. Take care to minimise pinholes in the pre-smoothed surface.
4. Mix the Complete Kit
Add all of the hardener to the resin container. Mix using a suitable power whisk and low-speed drill for approximately two minutes, scrape the sides and base of the container, and then continue mixing for a further two to three minutes until a uniform colour and consistency are achieved.
Mix only in full packs. Do not split the kit. Incomplete or incorrectly proportioned mixing can leave soft, uncured areas and render the membrane ineffective.
5. Apply Immediately
Once mixed, pour the product onto the prepared floor immediately. Leaving mixed epoxy inside the container significantly reduces its working time.
For readings above 85% RH and up to 98% RH, or commissioned underfloor heating screeds up to 90% RH, spread the membrane using the supplied 1.5mm × 5mm trowel at approximately 1.8m² per kg.
For readings up to 85% RH, use a STYCCOBOND A2 trowel at approximately 2.5m² per kg.
6. Back-Roll the Membrane
Immediately back-roll the applied F77 using a pre-coated paint roller. This flattens the trowel ridges and helps form an even, glossy, continuous and pinhole-free coating.
7. Allow the Membrane to Cure
At approximately 20°C, F77 can cure in around three hours. Cooler temperatures will extend the curing time. Do not proceed until the entire surface is hard, fully cured and tack-free.
Compatible Follow-On Products
Once F77 has fully cured, apply Stopgap P141 Primer neat before installing most Stopgap smoothing compounds.
Typical system:
Prepared cementitious subfloor → Stopgap F77 → neat Stopgap P141 → compatible Stopgap smoothing compound → flooring adhesive → floor covering.
On installations without underfloor heating, Stopgap 1200 Pro can be applied directly to fully cured F77 within 24 hours without P141. Where underfloor heating is present, prime the fully cured F77 with neat P141 before applying the selected compatible smoothing compound.
F. Ball STYCCOBOND B95 wood flooring adhesive may be applied directly to fully cured Stopgap epoxy waterproof surface membranes within 24 hours under suitable conditions, provided the surface is smooth enough and the complete installation meets F. Ball’s requirements.
Do not assume a Bona or another manufacturer’s adhesive can be bonded directly to F77. Unless the exact combination has been approved by the adhesive manufacturer, use F77 followed by P141 and a compatible Stopgap smoothing compound before applying the selected adhesive.
Choosing the Correct System
The correct system depends on the substrate, moisture reading, floor covering, underfloor heating and whether the surface requires repair or levelling. Contact our flooring specialists before ordering if you are unsure which products are required.
Important Information
- Apply Stopgap F77 only to a clean, absorbent and correctly prepared substrate.
- Do not apply it over calcium sulphate or anhydrite screeds.
- Do not use it where the subfloor is subject to hydrostatic pressure.
- Do not apply it directly over old bitumen adhesive residue. A suitable isolation and smoothing system may be required first.
- For mastic asphalt or another non-standard substrate, obtain project-specific guidance from F. Ball Technical Services.
- Do not bridge structural or movement joints with F77.
- Apply the membrane across the entire floor and terminate it correctly at the wall damp-proof course.
- The floor temperature must be above 10°C and the substrate must be at least 3°C above the dew point during application.
- Prevent trafficking until the membrane is fully cured.
- Underfloor heating must be correctly commissioned and switched off for 48 hours before, during and for 48 hours after installation of the membrane, smoothing compound and floor covering.
- Recommission underfloor heating gradually to prevent thermal shock.
- Always follow the latest F. Ball Technical Data Sheet and relevant British Standards.
Coverage, working and curing times are approximate and depend on temperature, substrate texture, porosity, application technique and site conditions. Never exceed the specified coverage rate. Product specifications and manufacturer recommendations can change, so always consult the latest technical information before use.