Hi, I am plastering a room in a 1938 -40 house. I have removed all the old plaster down to the bare wall. I was going to plasterboard the room out, then skim it. However when I worked out the price of plasterboard / PB adhesive and skimming it worked out much dearer than using Carlite Bonding and then skimming.
Apart from the time issue between the two methods, is their any other reason people apt for using plasterboard instead of bonding???
Thanks
It requires more skill to use a scratch (bonding) coat. However, if you know how to do it, it's generally regarded as a better job.
The dry lining technique makes it easier to add extra insulation to external walls, it is quicker, and requires less skilled plasterers.
Cos we can't plaster to save our lives?
Sadly true.
Had to cover red brick external walls in a conservatory last month. Fine says I, no problem. Just a few sheets of plasterboard and it's an easy job.
Everyone shakes their heads. No, we will get a plasterer to do it. Plaster looks much better.
Plasterer comes and you can guess what he did! :)))
Hey-ho.
It's quicker to dryline it, it also gives better thermal and acoustic insulation, it's easier to skim and gives a better finish, also I doubt whether your sums are right, bonding is over a fiver a bag and in an average sized room, you can expect to use at least 15 bags, that's provided you only put it on thin
Acoustically, wet plastering is better unless you can be sure that the perimeter of the wall is 100% sealed
I did one wall a couple of years ago with bonding then skimmed it, and it is still up and looks perfect. I don`t know how the professionals do it, nut I placed three 12mm vertical battens on each wall evenly spaced then applied the bonding coat. I then used a straight edge and ran it up the battens to make a perfectly flat vertical bonded wall. After it had dried out I took the battens off and filled in the gaps. I actually found this better than using plaster board, as the walls in that particular room where not very flat NOR straight.
Is this how it is normally done?? Thanks
No, except for DIY.
The scratch coat's job is to provide a flat vertical straight surface for the finish coat, regardless of the state of the wall. (Obviously, if the wall is too far from being straight or vertical, plaster isn't going to be able to correct this.) Fixing battens to the brickwork means you end up transfering any imperfections in the brickwork to the plaster face. This is often "good enough", but a plasterer is aiming to do better than this, i.e. correcting the imperfections in the brickwork.
I use an old technique called "dots and screed". You need a straight edge, spirit level, and 4 "dots". Dots are offcuts from the ends of laths, about 2" long. Given you don't find laths on building sites anymore, you'll have to make up 4 dots. Leave them floating in your water bucket until you need them. The "screed" is in effect your battens, but you make them out of plaster as you go.
Looking at the wall, work out where you want your screeds (battens). They need to be close enough that your straight edge reaches. Put 4 dollops of plaster on the wall about
1/4 of the way from each end of the screeds. Take the dots, and push them into the surface of each dollop just far enough so they don't fall out, largest face parallel to the wall. Hold your straight edge vertically with spirit level held in contact, and touch it against the surface of the dots. Tap the straight edge to push the dots into the dollops of plaster until the spirit level shows the faces are exactly vertical, and the gap under the straight edge is roughtly 0.5" from the wall (or whatever thickness scratch coat you want). Repeat for the other screed. Your dots are now the reference points for the surface of the scratch coat. The dollops of plaster will stiffen enough after some minutes that the dots become quite stable. Whilst that's happening, run two vertical lines of plaster between the dots, which will form the screed. Initially, make sure it's all proud of the dots. Use the straight edge to level it off with the dot surfaces. Again, whilst it's stiffening up, continue the screed lines to the floor and ceiling. Use the straight edge to level these off with the middle half of the screed.You now have your two battens, and they are vertical, rather than following the face of the wall. You now plaster just as you would with wooden battens -- fill in the middle first and level off with the straight edge, and then fill in the outside edges and level off against the middle section. The dots can be removed now (stab them with the corner of the trowel and they should come out).
If you need more than two screeds on a long wall, you get them all in a perfectly straight line by using a taught string across the dot faces. Look for the most proud part of the brickwork and check that it will be behind the scratch coat surface.
Platerboard has rubish thermal insulation , at least bonding couat has vermiculite in it. Acoustic insulation is awfull as anyone who has been in an office /hotel with stud partitions.
Solid masonary finish is IMO much nicer.
I agree on that one.
That's studding, we're talking about drylining, IE, using adhesive to stick boards to a masonry wall - the trapped air behind the PB is good insulation, ask any BCO.
Nicer maybe, but a PITA to apply, unless sand and cement is used as a backing plaster - bonding and browning really need to be skimmed the same day, any longer than 24 hours and the skimming sets as soon as it touches it.
But the cavity behind it insulates nicely. And when filled with rockwool, very nicely. Proper plasterwork, while of far better perceptual quality and more robust, misses the insulation opportunity.
And that insulation equates to a big (delayed) cost difference.
NT
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