Plastering: Your Options

What are the pros and cons of wet plaster against dry-lining? Mark Brinkley explains

Wet or dry?

Traditionally, homes in Britain have been treated to a wet plastered finish. The actual constituents of the plaster may have varied over the years — clays, lime renders, gypsum coatings, cement and Artex have all been used (and continue in use to this day), but the principle remains pretty much the same. Cover everything, trowel to a smooth finish and then wait to dry before painting or papering over. The problems with wet plastering are that it is a skilled job to apply (at least to do it properly), you have to wait for it to dry out and even when it does, it is prone to shrinkage and movement cracks: not popular with new homeowners.

In the past 30 years, there has been a big swing towards using dry plastering techniques, based largely on the ever increasing popularity of plasterboard. Sold in sheets 2.4m x 1.2m, plasterboard is quick to put up, is completely dry and can be finished with tape, sandpaper and paint. If you are wanting a surface against a timber stud or joist background, these days you more or less have to use a board finish, but increasingly builders are using plasterboard against masonry walls as well, where it gets stuck on in a process known as dot and dab. Why do this? Once again, it’s the attraction of a quick, dry process that can go more or less straight to painting.

Most plasterers using boards prefer to replicate a wet-plastered finish – which is undoubtedly better to decorate – by skimming over the board.

DIY options

Many hands-on self-builders plump for a wallboard called Fermacell. This is similar to plasterboard but is denser and heavier, which makes it good for soundproofing and allows you to fix heavy objects anywhere on the wall (unlike plasterboard, which requires either specialist fixings or searching out for the timber studs). But the main attraction for the DIYer is that it is very easy to finish: any gaps can be glued together, followed by a light sanding and it’s ready to paint. Fermacell is around three times the price of regular plasterboard, but it makes good financial sense if you plan to undertake the work yourself.

Screeding

Floor screeding is another skill traditionally carried out by plasterers. Again, it’s a skill that looks deceptively simple but which is notoriously difficult in practice. Traditionally, floor screeds are mixed on site, using a strong mix of cement and sharp sand, and laid over the floor slab below at a depth of 65mm or 75mm. It’s slow and relatively labour-intensive work.

Over the past decade or so, there has been a big switch to readymixed screeds, delivered to site by lorry. Not only is the quality of the mix ensured, but you are able to order enough for a day’s screeding, thus minimising waste. Ready-mixed screeds are slightly more expensive than using materials mixed on site (e.g. £100/m³ vs £80/m³) but save money in reducing the work of a labourer.

A further development is the uptake of gypsum-based or calcium sulphate screeds, as opposed to cement ones. These are much easier and quicker to lay and they achieve good strength with shallower depths, typically 50mm instead of 75mm. However, there is a price premium — the cost is around £150/m³. All forms of screed take a considerable amount of time to dry out: expect to leave a screed open for at least 70 days before it is suitable for applying a floor cover to it.

*Correct as of January 2008

Further reading:

• How to patch up plaster
• The trades explained: The Plasterer
• DIY plastering