Ready Reference: Plasters and Wall Fillers
WHICH FILLER TO USE
Celluloseor ready-mixed for:
• superficial cracks in plaster and plasterboard
• small holes (up to 50mm/2in) across
• gouge marks in plaster
• joint cracks in plasterboard or coving
• filling dents and cracks in wood to be painted.
Finishing plaster or brush-on skim plaster for:
• large holes (over 50mm/2in) across
• deep cracks in plaster
• patches where unsound plaster has been stripped off
• skim coats on plasterboard.
Wood stopper in matching shade for:
• wood to be given a natural finish.
Flexible mastic or ready-mixed filler for
• gaps between woodwork and walls (round windows and door frames).
TOOLS FOR MAKING GOOD
• a filling knife with a 25-50mm (1-2in) wide blade. This has a more flexible blade than a wallpaper stripping knife, and is useful for small repairs
• a hawk for holding plaster close to the work (something you can make yourself from a square of450 x 450mm with a piece of thick dowelling for the handle)
• a plasterer’s trowel (also called a steel float) used for applying plaster and polishing the surface
• an angle trowel is also useful for making neat right-angled internal corners
WHICH FILLER IS WHICH?
Celluloseare based on plaster with added cellulose resins to improve flexibility, adhesion and reduce drying time.
• remains workable for up to 1 hour
• it will shrink, so cracks should be overfilled and sanded back
• expensive to use in large quantities
• dries white.
Ready-mixedare like ordinary cellulose , but with added ingredients to improve performance and sold in plastic tubs.
• quick-drying in thin layers (thick layers may take up to 24 hours)
• less likely to shrink or slump
• waterproof, so can be used in wet areas or outdoors
• relatively expensive to use in large quantities.
This is made from gypsum (calcium sulphate) and numerous different types are available.
• for most repair jobs, Sirapite or similar finishing plaster is ideal
• available in bags from 5kg (11lb) upwards
• relatively inexpensive for large repairs
• very quick setting (less than 30mins)
• may shrink in deep cracks or thick layers
• dries grey or pink.
Brush-On Skim Plaster
Brush-on skim plaster, specially-formulated and ready-mixed, is designed to be brushed on and smoothed with a spreader instead of.
• remains workable for up to 4 hours
• doesn’t shrink or crack
• more expensive than plain plaster
• dries white.
Wood stoppers are resin-based ready-mixed fillers designed for wood that’s going to be varnished.
• sets quickly with little shrinkage
• dries wood-colour but can take stain.
Flexible mastics are rubber or acrylic-basic sealants designed for gaps between walls and woodwork where sight movement would crack ordinary fillers.
• remains flexible without shrinking
• can be painted
• available in different colours.