Plastering is sometimes a supply-and-fix trade but, with the rise in popularity of dry-lining, it has tended to slip back into being a labour-only trade. Plasterers are probably one of the hardest trades to locate and they are always busy, so you will need to identify who’s going to be doing your plastering at the earliest possible stage and then keep in touch with them to advise them on progress.
The walls of timber frame, steel frame and SIPs (structural insulated panels) houses are almost always finished with 12mm plasterboard fixed to the vertical studs or counter battens. Those building in masonry have the choice of either hard (wet) plastering the walls or dry-lining with 12mm-thick plasterboard fixed to the walls with dabs of Gyproc adhesive. Along with the cost disadvantage of hard plaster (SEE BELOW), there is also the fact that it takes twice as long to do the work and it can take an inordinately long time to dry out, necessitating a three-to-four-week delay in the winter months. Cracking through drying out is also much more likely with a hard-plastered wall. Walls are usually costed right through – i.e. ignoring the openings for windows and doors – and this compensates for the reveals.
Ceilings are finished with plasterboard and it has become standard practice to use 15mm plasterboard, which does away with having to introduce noggings at each joint and at the perimeter. Fixing these days is almost always by drywall screws rather than nailing and this preserves the integrity of the board.
Both walls and ceilings are skim-coated with plaster. On a hard-plastered wall, this skim coat will be applied as a 3mm base plus a 2mm finish to the substrate of either sand and cement or proprietary base coat. For plasterboard walls and ceilings, the joints between the boards are first of all taped with an adhesive fibre tape before a 3mm-thick plaster topcoat is applied. In high-density housing, a tapered-edge board is used with the joints simply taped and skimmed over, but that is not really satisfactory for a better quality home. Ceilings are usually set with a 3mm plus 2mm smooth plaster finish over the taped boards.
External walls to be rendered are usually given two coats of a sand and cement mix, which contains a waterproofer. This then has to be painted with an exterior paint. The scaffolding has to be independent with no putlogs and will also stay up for the painter.
Floors are commonly screeded with a sand and cement mixture, either mixed on site or delivered ready mixed. It can then either be barrowed in or pumped in to be levelled out by hand. This is time consuming and labour intensive and with underfloor central heating pipes, potentially damaging. There has, therefore, been a move towards the use of self-levelling screeds, usually a calcium sulphate mix, that are pumped in by specialist contractors.
The attic is costed as having the stub walls, sloping and flat ceilings plasterboarded and skimmed.
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|200 sheets 12.5mm plasterboard @ £3.84 each||£768.00|
|VAT @ 20%||£153.60|
|80 x 25kg bags plasterboard adhesive @ £4.60 each||£368.00|
|VAT @ 20%||£73.60|
|10 rolls self-adhesive fibre tape @ £4.35 each||£43.50|
|VAT @ 20%||£8.70|
|30 skim beads @ £1.06 each||£31.80|
|VAT @ 20%||£6.36|
|54 bags plaster finish @ £3.60 per bag||£194.40|
|VAT @ 20%||£38.88|
|Plasterer plus labourer, 20 days @ £267.04 per day||£5,340.00|
|Ceilings and stub walls to loft|
|130 sheets 15mm plasterboard @ £5.20 per sheet||£676.00|
|VAT @ 20%||£135.20|
|4 boxes 32mm drywall screws @ £4.55 per box||£18.20|
|VAT @ 20%||£3.64|
|7 rolls self-adhesive fibre tape @ £4.35 each||£30.45|
|VAT @ 20%||£6.09|
|36 bags plaster finish @ £3.60 per bag||£129.60|
|VAT @ 20%||£25.92|
|Plasterer plus labourer, 10 days @ £267.04 per day||£2,670.40|
Floor insulation and screed
The insulation for the ground floor has already been costed for within Part 3: The Floor Structure. The insulation to the eaves and the stub walls in the attic has already been costed for in Part 5: The Roof. The beam and block first floor is costed here with 50mm insulation beneath the screed, and the ceiling joists beneath the loft floor have 100mm mineral wool insulation beneath the decking.
38 sheets 50mm flooring insulation @ £13.50 per sheet £513.00
VAT @ 20% £102.60
6 rolls 100mm mineral wool insulation @ £11.99 per roll £71.94
VAT @ 20% £14.39
5 rolls foil tape @ £6.77 each £33.85
VAT @ 20% £6.77
Ganger plus labourer, 1 day @ £27.63 per hour £221.04
Supply-and-fix self-levelling screed @ £16.79/m² £3,811.33
The external render is taken down to the waist/plinth course of proud bricks and render stop beading is, therefore, not required on this building. If it was, then you would need 15 lengths of beading at £2.53 each and it would add a day’s labour for a single plasterer’s labourer at £100.
4 bags plasterer’s sand @ £6.16 per bag £24.64
VAT @ 20% £4.93
48 bags Portland cement @ £2.90 per bag £139.20
VAT @ 20% £27.84
13 render angle beads @ 95p each £12.35
VAT @ 20% £2.47
Plasterer plus labourer, 5 days @ £267.04 per day £1,335.20
|(of which recoverable VAT)||£610.99|
Why not wet plaster?
Hard (wet) plastering fans prefer the solidity and durability that it offers, but it is more expensive. On our benchmark house, the extra cost of using hard plaster with a proprietary base coat plaster would amount to some £2,250.
How to reduce these costs
- If you took on the job of laying the insulation to the first and loft floors, there would be a saving of £221 which, added to the cost of installing the insulation to the ground floor, would mean a total saving of £538.
- Switching to a sand and cement screed would save around £580. But the mirror-flat surface that the self-levelling screed produces speeds up the laying of floor tiles etc.
- The resourceful self-builder might also consider taking on all or part of the tacking or, at the very least, working with the plasterers by helping to cut the boards.
Our Benchmark House
The floorplan for the house costed within this series measures up at 227m² — much larger than the average family home. Four bedrooms on the smaller first floor share three bathrooms. Downstairs, the living spaces flow easily onto one another, with an open plan family kitchen being the hub of home life.
All prices correct at time of writing, November 2011
Special thanks to Estimators Limited (estimators-online.com 0161 286 8601) and Design & Materials Limited (designandmaterials.uk.com 0845 404 0400) for their help in the preparation of this series of articles.