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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Free Next Working Day Delivery
Free Next Working Day Delivery
- Free Next Day Delivery on all orders (Please note that occasional delays may occur due to courier disruptions or stock availability).
- Orders placed before 3 pm will be dispatched on the same working day for delivery the next working day.
- Orders placed after 3 pm on Fridays will be dispatched first thing on Monday for delivery on Tuesday.
- Small items are shipped via Royal Mail with 24-hour tracked delivery.
- Large and oversized items are shipped via FedEx with next day tracked delivery.
- Tracking information will be provided via email or text once your order has been dispatched.
- We deliver to mainland UK only.
- Orders placed for delivery on a bank holiday or during our closure period will be dispatched on the next standard working day.
- Exclusions: Levelling compounds are not eligible for delivery
Click & Collect
Click & Collect
- Place your order online.
- Select the click & collect option at the checkout.
- You will receive email confirmation that your order is ready to collect (generally within 5 minutes)
Opening hours: 7am - 4pm Mon-Fri
Collection address:
Wiltshire Wood Flooring Supplies
Unit 1
Penton Business Park
Stephenson Road
Churchfields Industrial Estate
Salisbury
SP2 7NP
F. Ball Stopgap F77 is a professional, solvent-free, two-part epoxy damp proof membrane designed to control residual construction moisture and rising damp in concrete and sand/cement screeds before installing smoothing compounds, adhesives and floor coverings.
Applied as a single coat, F77 can provide moisture protection 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.
Why Choose F. Ball Stopgap F77?
- Professional two-part epoxy waterproof surface membrane.
- Controls residual construction moisture and rising damp.
- Single-coat application at readings up to 98% RH.
- Suitable over 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.
- Can allow earlier installation of wood flooring and other 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.
- Ground-floor installations affected by rising damp.
- Domestic renovation projects.
- Commercial and fast-track flooring installations.
- Cementitious underfloor heating screeds that have been correctly commissioned.
- Projects receiving wood flooring, LVT, vinyl, carpet or other suitable floor coverings.
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 mechanically prepared cementitious surface. Concrete or sand/cement screeds should be free from laitance, surface hardeners, adhesive contamination, oil, grease and other materials that could prevent adhesion.
The finished membrane must form a continuous, glossy black coating without pinholes, weak areas or missed sections. The specified coverage rate must not be exceeded, as spreading the product too thinly may prevent it from providing the required moisture protection.
Coverage and Application Guide
| Subfloor Moisture Level | Application Rate | Application Trowel | 7kg Coverage | 14kg Coverage |
|---|---|---|---|---|
| Up to 85% RH | Approximately 2.5m² per kg | STYCCOBOND A2 trowel | Approximately 17.5m² | Approximately 35m² |
| Up to 98% RH | Approximately 1.8m² per kg | 1.5mm × 5mm trowel supplied with the kit | Approximately 12.5m² | Approximately 25m² |
| Underfloor heating screeds up to 90% RH | Approximately 1.8m² per kg | 1.5mm × 5mm trowel supplied with the kit | Approximately 12.5m² | Approximately 25m² |
One Coat – Different Application Weights
Stopgap F77 is a one-coat system at both application rates. A higher relative humidity reading does not require two standard coats. Instead, the product is applied at a heavier coat weight using the supplied 1.5mm × 5mm trowel.
After trowelling, immediately back-roll the epoxy with a pre-coated paint roller to flatten the ridges and create an even, continuous and pinhole-free membrane.
Very absorbent surfaces can draw resin into the subfloor and leave a subdued finish. Where pinholes, weak areas or insufficient coverage remain visible, an additional application may be required.
Technical Specifications
| Product Type | Two-part epoxy waterproof surface membrane |
|---|---|
| Available Sizes | 7kg and 14kg kits |
| Components | Pre-measured resin and hardener |
| Colour | Glossy black when correctly mixed and applied |
| Maximum Moisture Reading | Up to 98% RH on suitable cementitious subfloors |
| Underfloor Heating | Up to 90% RH at an application rate of approximately 1.8m² per kg |
| Working Time | Approximately 30 minutes at 20°C once mixed and poured onto the floor |
| Curing Time | From approximately 3 hours at 20°C |
| Minimum Floor Temperature | Above 10°C during application |
| Application | Specified notched trowel followed immediately by back-rolling |
| Suitable Substrates | Prepared, clean and absorbent concrete and sand/cement screeds |
| 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 moisture reading determines the required application rate and coverage.
2. Mechanically Prepare the Surface
Remove laitance, surface treatments, weak material and contamination by suitable mechanical preparation. Power-floated concrete must be mechanically prepared to expose a clean, lightly textured and absorbent surface.
New concrete and sand/cement screeds should normally be left for a minimum of seven days before preparation and application of the membrane.
3. Repair or Pre-Smooth Where Required
Rough, uneven or damaged cementitious subfloors should be repaired or pre-smoothed before applying F77. Suitable products can include Stopgap 1200 Pro or another compatible Stopgap repair or smoothing compound 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. Care should be taken to avoid pinholes within 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 consistent colour and appearance are achieved.
Do not split the pack unless the resin and hardener can be measured in the manufacturer’s exact proportions. Incomplete mixing can leave soft, uncured areas and prevent the membrane from performing correctly.
5. Apply Immediately
Once mixed, pour the product onto the prepared floor immediately. Leaving mixed epoxy inside the container significantly reduces its working time and can cause it to heat and cure rapidly.
For readings up to 98% 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 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 fully 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.
What Goes Over Stopgap F77?
F77 Followed by a Smoothing Compound
Once the F77 has fully cured, apply Stopgap P141 Primer neat before installing most Stopgap smoothing compounds. P141 dries to a hard, textured surface that promotes adhesion between the non-absorbent epoxy membrane and the smoothing compound.
A typical system is:
Prepared cementitious subfloor → Stopgap F77 → neat Stopgap P141 → compatible Stopgap smoothing compound → flooring adhesive → floor covering.
Stopgap 1200 Directly Over F77
Stopgap 1200 Pro can be applied directly to fully cured Stopgap F77 within 24 hours of the membrane curing, without first applying P141.
The 24-hour period is the maximum direct-application window and not an additional waiting time. For example, where the F77 becomes fully cured and tack-free after approximately three hours, the 24-hour window starts from that point.
Direct Bonding Wood Flooring with STYCCOBOND B95
F. Ball STYCCOBOND B95 wood flooring adhesive can be applied directly to a fully cured Stopgap epoxy waterproof surface membrane within 24 hours of the membrane curing, provided the surface is smooth enough to receive the flooring and all other installation requirements are satisfied.
A direct wood-flooring system can therefore be:
Prepared cementitious subfloor → Stopgap F77 → STYCCOBOND B95 → suitable wood flooring.
If the subfloor requires levelling, the correct system would normally be F77 followed by P141 and a suitable smoothing compound before the wood flooring adhesive is applied.
Using Bona or Another Manufacturer’s Adhesive
Do not assume that a Bona or other third-party wood flooring adhesive can be bonded directly to Stopgap F77 simply because it is a reactive or silane-based adhesive.
Unless the adhesive manufacturer has confirmed the exact combination in writing, the safer mixed-manufacturer system is:
Stopgap F77 → Stopgap P141 → compatible Stopgap smoothing compound → selected wood flooring adhesive.
This provides a conventional prepared smoothing-compound surface for the adhesive and avoids relying on an unconfirmed direct bond between products from different manufacturers.
P141 Primer or Kiln-Dried Grit?
Epoxy damp proof membranes have traditionally sometimes been blinded with clean kiln-dried grit while the epoxy is still wet. The grit becomes embedded in the resin and creates a mechanical key for a subsequent smoothing compound.
For most modern F. Ball installations, the cleaner and simpler system is to allow F77 to cure fully and then apply Stopgap P141 Primer neat. P141 contains recycled uPVC particles and dries to a textured surface designed specifically to promote adhesion to non-absorbent substrates, including Stopgap waterproof surface membranes.
Do not add or broadcast grit unless it forms part of a project-specific specification or has been recommended by F. Ball Technical Services. Using P141 avoids loose or poorly bonded aggregate and makes it easier to achieve a controlled, consistent surface.
Recommended Levelling Compounds
Stopgap 1200 Pro – A two-part smoothing compound particularly suited to refurbishment work. It can be applied directly to cured F77 within the specified 24-hour window.
Stopgap 300 HD – A heavy-duty smoothing compound for preparing internal subfloors in demanding domestic and commercial areas. Apply over cured F77 using the correct primer and system guidance.
Stopgap 700 Superflex – A flexible, fibre-reinforced smoothing compound for suitable timber, steel and mixed subfloor installations. Apply only as part of the correct specified build-up.
Stopgap Fast-Track 30 – A rapid-setting smoothing compound for time-sensitive installations. Use over F77 only with the required primer and in accordance with the current technical data.
Need Help Choosing?
The correct system depends on the subfloor, 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 F. Ball products are required for your installation.
Important Information
- Stopgap F77 must be applied to a clean and absorbent cementitious substrate.
- Do not apply it directly over old bitumen adhesive residue.
- Do not describe old black adhesive residue as a suitable base simply because F77 is an epoxy product.
- Mastic asphalt is a finished flooring substrate made using bitumen and aggregate; it is not the same as a thin layer of bitumen adhesive residue.
- Sound asphalt normally requires an appropriate smoothing-compound system rather than direct application of F77.
- For bitumen adhesive residues, Stopgap 1200 Pro may be suitable where the residue is firm, thin and well bonded, subject to full preparation guidance.
- 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 remain above 10°C during application.
- The underfloor heating system must be fully commissioned before installation.
- Underfloor heating should be 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 and curing times are approximate and depend on the temperature, substrate texture, porosity, application technique and site conditions. The specified coverage rate must not be exceeded. Product specifications and manufacturer recommendations can change, so always consult the latest technical information before use.
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