Cracked, patchy or tired walls leave most homeowners wondering whether a quick skim will do or whether the old plaster has to come off entirely. Getting this call right saves money and avoids a finish that fails within a year. Here is how we judge it on jobs across Pontypridd and the Rhondda valleys.
Skimming is a thin 2 to 3mm coat of finish plaster applied over an existing sound surface, whether that is old plaster, plasterboard or a stable painted wall that has been prepared and PVA'd. It flattens minor damage and gives you a smooth base ready for paint.
Full replastering means hacking off the old plaster back to the brick or block, then rebuilding with a bonding or browning undercoat followed by a finish skim. It is far more disruptive and dusty, but it is the only real fix when the substrate itself has failed.
If the existing plaster is firmly stuck to the wall and the problems are cosmetic, a skim is usually the sensible, cheaper choice. Tap across the wall with your knuckles: a solid, dull sound is good news.
Some faults sit in the substrate, and no amount of skimming will hide them for long. In older Valleys terraces we often find lime plaster that has lost its key, or areas damaged by past damp.
As a rough guide, skimming an average bedroom wall is quicker and lighter on the wallet, while full replastering can cost two to three times more per room because of the labour in hacking off, disposal and the extra undercoat stage. Prices vary with access, ceiling heights and how much making good is needed, so treat any figure as a starting point until we have seen the room.
Timing matters too. A skimmed room can often be painted within a few days once fully dry, whereas freshly replastered walls need longer to dry out, sometimes two to four weeks before painting, especially in cooler months. Rushing paint onto green plaster is a common cause of flaky, patchy finishes.
When in doubt, get someone to look before committing. A ten minute inspection tapping the walls and checking a few suspect areas usually settles it, and it stops you paying for full replastering you did not need or skimming that will not last. If damp is involved, deal with the source first, because plastering over an active leak or rising damp simply wastes the work.
Sometimes, if the lime plaster is still sound and well keyed, though it needs the right preparation and a suitable bonding agent. If it is soft or blown, it is better hacked off and rebuilt.
A skim coat is often ready within a few days, while full replastering may need two to four weeks to dry fully. Use a breathable mist coat first rather than neat emulsion.
Generally yes, because there is no hacking off, waste disposal or undercoat stage. Full replastering can cost roughly two to three times more per room, but it is the right choice when the old plaster has failed.