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SKU: STOPGAP12105

Stopgap P121 Primer - 5L

£37.53
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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

  • 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 P121 is a high-performance acrylic primer developed to prepare calcium sulphate (anhydrite) screeds before the application of Stopgap smoothing compounds and compatible flooring adhesives. It improves adhesion, controls substrate absorbency and helps prevent unacceptably rapid drying of smoothing compounds and adhesives.

Its distinctive blue colour provides excellent visual coverage during application, helping to ensure the entire floor has been primed evenly. Stopgap P121 is non-flammable, easy to apply and suitable for use over normal underfloor heating systems.

Why Choose F. Ball Stopgap P121?

  • Specifically developed for calcium sulphate and anhydrite screeds.
  • Promotes excellent adhesion of smoothing compounds and adhesives.
  • Controls substrate absorbency.
  • Helps prevent rapid drying of adhesives and smoothing compounds.
  • Blue colour provides visual control during application.
  • Easy to apply by roller or brush.
  • Non-flammable formulation.
  • Suitable over normal underfloor heating installations.

Ideal For

  • Calcium sulphate screeds.
  • Anhydrite screeds.
  • Preparing subfloors before Stopgap smoothing compounds.
  • Reducing substrate absorbency.
  • Domestic flooring projects.
  • Commercial flooring installations.
  • Underfloor heating systems.

Professional Advice

Calcium sulphate screeds require the correct preparation before levelling compounds or adhesives are applied. Stopgap P121 is specifically formulated for these substrates and helps provide a consistent, well-bonded surface for the next stage of your flooring installation.

Once primed, choose the appropriate Stopgap levelling compound depending on your project requirements, substrate type and installation times.

Technical Specifications

Product Type Acrylic Primer
Pack Size 5 Litres
Colour Blue
Application Method Brush or roller
Coverage Approximately 40m²–60m² per 5L depending on substrate porosity*
Drying Time Approximately 1 hour under normal conditions*
Suitable Subfloors Calcium sulphate (anhydrite) screeds.
Underfloor Heating Suitable for normal underfloor heating installations.
Flammability Non-flammable.

Prepare Your Subfloor Like a Professional

Correct preparation is essential for a smooth, durable and long-lasting flooring installation.

1. Check for Moisture

Ensure the screed has reached the manufacturer's recommended moisture content before priming or installing floor coverings.

2. Prime the Surface

Apply Stopgap P121 evenly across the prepared calcium sulphate screed. The blue colour helps ensure complete and consistent coverage.

3. Repair Any Imperfections

Use Stopgap Micro Rapid for minor repairs and feather edging, or Stopgap 400 Repair for larger repairs before levelling.

4. Choose the Right Levelling Compound

Stopgap Fast-Track 30 – Ideal when speed is the priority.

Stopgap 700 Superflex – Flexible formulation for timber and plywood.

Stopgap 1200 Pro – Excellent for refurbishment projects over suitable adhesive residues.

Stopgap 300 HD – Heavy-duty smoothing compound for demanding environments.

Need Help Choosing?

Not sure which primer your subfloor requires? Contact our flooring specialists with details of your substrate and we'll help you choose the correct preparation system.

Important Information

  • For internal use only.
  • Apply only to clean, sound and correctly prepared subfloors.
  • Allow the primer to dry before applying smoothing compounds or adhesives.
  • Always follow the latest F. Ball Technical Data Sheet.
  • Coverage varies depending on substrate porosity.

*Coverage and drying times are based on normal site conditions. Highly porous substrates, lower temperatures or increased humidity may affect performance.

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