Home > Companies > Ball, F and Co Ltd > Stopgap 300 H D

A self-smoothing, low odour, protein-free underlayment.

Designed for preparing sound interior subfloors for the installation of new coverings. Suitable for heavy duty and biologically sensitive areas.

Can be used on:

  • Absorbent surfaces, e.g. concrete, sand:cement screeds, synthetic anhydrite screeds.
  • Non-absorbent surfaces, such as asphalt, granolithic, terrazzo, steel, epoxy and polyester resins, ceramic and quarry tiles to provide a layer of absorbent material.
  • Surfaces contaminated with minimal quantities of adhesive residues.


  • Can be applied unfilled (i.e. without aggregate) from between 2-15mm, Stopgap graded aggregate can be used for economy up to 20mm thickness.
  • Can be applied by hand or with suitable pump equipment, and can be spread down to a feather edge.
  • Trowel marks should be removed by rubbing with a carborundum stone before the underlayment has fully hardened, i.e. approximately one and a half hours after application.
  • Underlayment must be dry before laying floorcoverings.

Related literature

The following content references this product:


Preparation products:

All surfaces must be primed before applying underlayment. F Ball and Co. manufactures suitable primers/ sealers for most surfaces:

– Stopgap P131 General Purpose Neoprene Primer:

A neoprene emulsion primer designed:

  • To promote adhesion of Stopgap smoothing underlayments to smooth, non-absorbent surfaces such as steel, epoxy and polyester floors.
  • For use on absorbent surfaces, such as concrete, sand/cement screeds, flooring grade particleboard, plywood, hardboard, and non-absorbent surfaces of terrazzo, power floated concrete, quarry tiles, ceramic tiles, asphalt, steel, galvanized steel, ungritted Stopgap F75 and Stopgap F76 waterproof surface membranes, epoxy, polyester and existing adhesive residue.
  • For use over normal underfloor heating installations.

The product is non-flammable, protected against biodegradation, and pigmented to allow visual control of coverage.

NBS Specification

NBS Create logo
This product is associated with the following NBS Create clause:
45-55-10/320 Smoothing or levelling underlayment compound

Product specification

An important note about specifying



Ball, F and Co Ltd


+44 (0)1538 361633

Product reference

Stopgap 300 HD

Preparation products

Stopgap P131 primer

Manufacturer details

Churnetside Business Park,
Station Road,
Staffordshire, ST13 7RS
Tel +44 (0)1538 361633
Fax +44 (0)1538 361622
NBS Plus
NBS National BIM Library