Can you plaster over wallpaper? You are not meant to plaster over wallpaper as the water in the plaster mix soaks the paper and loosens it, also you are not in direct contact with the background. Plaster takes nearly 3 hours to set so it would be soaking the paper for all this time and paper as you know is porous.
I have in the past however seen wallpaper that has been skimmed over. The plasterer applied p.v.a adhesive and gambled that it would hold , it did look ok but I think that the wall paper was painted in oil based paint .
Colleges will tell you its a BOTCH just like wall papering over existing wall paper .
How much time do you get to work with plaster ? Once mixed finish plaster takes between 2.5 and 3.5 hours to set, so even a small area takes a considerable amount of time to complete as you can`t attain a good finish until it has nearly set hard.
How long before I can paint my new plaster? If you have had an area skimmed you should be able to paint it after around 2 to 3 days depending on the time of year it will take longer to dry in winter, you should let the plaster dry naturally.If you have had both an undercoat plaster and a skim coat of plaster applied directly to brick or block work you can estimate a drying time of around 7 days,again the room temperature will effect this.
Can you plaster over painted walls? Yes providing pva adhesive is applied prior to plastering and any loose or flacky paint is scraped off.
white wash or distemper must be removed before plaster can be applied.You can usually wash it off with warm water and a sponge then apply a good coat of p.v.a prior to a finishing plaster.
Can you plaster over textured patterns? Yes providing that they are not too heavy. Finish plaster can be applied to around 3-4 mm. so if the texture is scraped back with a heavy duty Razor scraper you can cover the majority of patterns.You should take into account that many people apply texture to hide bad bumpy ceilings and walls so make sure that the overall shape of the background you want smoothed is quite flat as a smooth finish will show imperfections.
My ceilings have very bad cracks in them, can they be plastered? The only remedy for really bad and cracked ceilings is to either pull down the ceiling and replace it with a New one or locate the joists and screw new plasterboard directly over the existing ceiling. if doing the latter Care must be taken to stagger the joins so that you are spanning the cracks that are alteady there . In other words screw the boards up in a different pattern than they are now.
If it is possible to screw new plasterboards over the existing ceiling you will avoid a lot of mess and additional cost of removing the rubbish.Over boarding will also give improved fire protection and better soundproofing. (Warning ) though ,Care must be taken to avoid drilling through pipes or wires, its easily done !!! Trust
Faint cracks can have reinforcing tape known as scrim applied to them prior to plastering, this often stops the cracks opening up again but you can never be 100% sure.First floor ceilings receive more vibration so are more prone to cracking.
I have removed Tiles from my walls and they have left a terrible mess, Can it be repaired? Yes you can usually repair this damage using carlite bonding to patch it back in. If there has been substantial damage to the plasterboard you can often patch in a new peice of board and then re skim.
Outside Rendering- how many coats?
Outside rendering requires 2 separate layers of sand and cement. The first coat is called a scratch coat. This coat usually incorporates a waterproof admix which allows you time to work the surface of the 2nd and final coat. This coat is applied at least a day after the scratch coat. The 2nd coat is leveled using a straight edge and it is then buffed up using a plastic trowel known as a float, you can achieve a good finish by passing a sponge over the floated area once it has hardened sufficiently. Make no mistake this is quite a skill and takes time to perfect. In winter it is best to incorporate a suitable frost inhibitor in the mix.