The traditional way of finishing off masonry walls, and a technique still favoured by many plasterers, wet plastering includes utilizing either a cement-based render or a gypsum backing which is trowelled directly onto the bricks or blocks.To start with, a scratch coat is applied, alternatively known as a ‘key’ coat. This is the base coat that is softly scratched while the plaster remains wet to make a good key for the second layer of plaster - the ‘skim’ coat - to adhere to.
In addition to cement-based and gypsum plasters, lime and clay plasters are favoured by many traditionalists and those desiring a wall that can breathe. Lime and clay plasterers in devon are higher in price than ‘conventional’ wall surface finishes and it is a good idea to use only a plasterer with experience of these materials.
Something to be aware of though: if you are going to be applying the technique of wet plaster upon an outside wall, do consider that you are not able to add insulation as you're able to with plasterboard - except in cases where you are happy to use exterior insulation on your property. So, if you currently have solid brick walls - as opposed to cavity walls - you must look into the effect that a lack of insulation may have.
Gives an even, hardwearing finish
Suits traditional properties perfectly
Simple to apply around difficult areas for instance windows and doors
Offers outstanding airtightness and soundproofing
Can't add insulation internally behind this type of plaster
Takes more time to dry out compared with various other methods
Hairline cracking can take place
High skill level is essential - a skilled plaster can be difficult to come across and will most likely ask for more for this specific sort of work.
Plasterboard with Skim Coat
There are a couple of standard board thicknesses of plasterboard - 9.5mm for 400mm spacings and 12.5mm for 600mm. There's also numerous different methods by which plasterboard might be fixed to a wall: ‘dot and dab’ or ‘board on dabs’, and plasterboard that is screwed to timber battens fixed to the wall.
By using dot and dab, sheets of plasterboard are stuck to either brickwork or blockwork walls working with dabs of adhesive and permitting just a small cavity between the plasterboard and the wall. Using the batten method - ideal for those wanting to add insulation to a solid wall - timber battens, usually measuring 38mm wide along with a depth to support the thickness of insulation you are using between them, are screwed to the wall.
Rigid board PIR (polyisocyanurate) insulation is then put between the battens just before the plasterboard is fixed over the top. A vapour control layer is also needed in the instance of solid walls.
Finally, the joints between the boards are lined with scrim tape - typically in the style of a self-adhesive tape - just before a skim layer of plaster is trowelled on to the plasterboard.
Hairline cracks - which are often linked with wet plaster - are unlikely
Quicker drying out time
Achievable to carry out on a DIY basis
Insulation can be fitted behind plasterboard
The cavity made can eat into room space
Can be tough to fix shelving, radiators and pictures
Provides not much in the way of airtightness
Scrim won't always mask the space between the sheets of plasterboard which could be evident through the skim coat.
As opposed to having a skim finish applied to plasterboard, it can be quite possible to use the plasterboard itself as your final finish - in fact, this is common in the US and in more and more developer houses in the UK also.
In the example of taping and jointing, tapered-edge board is ordinarily selected. Joints are taped and next filled over, as are any screw or nail holes. The whole surface is then sanded before painting. It is quick, comparatively affordable and crack-free.
Quicker and less sloppy as opposed to other techniques
Ends up a little cheaper as no plasterer is essential
Can be executed on a DIY basis
The final finish is rougher and a little dull, even if painted
Walls feel hollow if tapped and lack the solid-feel of plastered walls (especially when applied on stud walls)
Plasterboard is easily damaged and difficult to mend