Scrim

[plasticpigeon]

As i am now going to plaster my front room myself, I thought I would experiment a bit. The celing is cracked and has some rather stubborn gloss painted lining paper stuck to it that I have only managed to take off in parts. Rather than do the conventional thing and overboard, as it seems very solid, just cracked in places, I thought perhaps I could scrim the whole lot and plaster over. I've found this 1m wide scrim online. Has anyone got any experience of this and does it sound a good idea?

http://build.lsd.co.uk/plasterers-scrim-self-adhesive-fibreglass-tape-1000mm-x-25m

 

[Feltwell]

Not sure, to be honest. If you're in doubt then overboarding and skimming is relatively quick and cheap, and well proven. Whilst the ideal is repairing the original ceiling, at least overboarding leaves it intact, and visually you can't tell the difference. So long as decent joint tape is used - preferably the paper type rather than the self-adhesive mesh type - joints don't crack unless the building moves a lot.

In saying this I am presuming you have no cornice. If you have, then it's no contest in my mind - repair the original ceiling.

Who the hell thought it was a good idea to gloss paint a ceiling? Past owners - we have so much to be thankful to them for. :roll:

 

[Zebra]

I am using this stuff - a larger pattern of mesh, but the same thing - where I'm lime plastering over woodfibre boards. Because the woodfibre boards are quite soft, it gives stability to the first coat. You push it in to the first coat while it's still soft, before the application of the second. The stuff I'm using isn't adhesive though.
Are you going to scrim and lime plaster, or gypsum?

 

[Me!]

I use the 2" wide version of that scrim for doing all joins in plasterboard and I think it works very well for that.
However, it isn't very sticky. Only sticky enough really to hold it in place until the plaster goes over it and the plaster then sticks to the plasterboard. So, do you think the new plaster will stick well enough to the existing gloss paint and paper? I have no experience of trying this, but I don't think I'd want to risk it personally.

 

[Penners]

PP - if you're gypsum plastering over a plain ceiling that already has a substrate of gypsum plaster, then as Me! says I wouldn't rely on the adhesive scrim to get the plaster to stick. I would paint the ceiling with a coat of PVA, and then add some PVA to the plaster mix.

However, I completely agree with Feltwell's comments about cornicing.

 

[plasticpigeon]

No cornices here, it is a humble little house. The ceiling is gauged lime plaster on lath. I absolutely hate overboarding. I saw one plasterer doing my back room miss the joists around 70% of the time, and with all those nails in the laths and the joists only 2 - 3" wide, when he did get a joist he often hit a nail too. It is almost impossible to get the boards lining up on the joist so at least one edge is hanging in space and it absolutely knackers the lime ceiling underneath when it is nailed or screwed as the original ceiling is often not totally flat.

 

[Feltwell]

I overboarded (underboarded?) my attic room ceilings - partly because the lath &plaster ceiling was in a poor state, but mostly because it was the only way to insulate the roof, using insulated plasterboard.

I suspect I took much more care than your average plasterer - I marked the walls beforehand at the ceiling junction with where the joists / rafters were, finding them with a stud detector but more often just by probing with a bradawl. Then once the plasterboard was propped in place I was able to transfer the marks onto it and draw a line for the joist/rafter centre. I screwed the plasterboard in place rather than nailing - the screws didn't really have any problem if they hit a nail, they just pushed past. I also took a line of plaster off the top of the walls so the new boards went right up to the brick, filling the gap back in afterwards. Boards were cut so that joints always fell on a rafter for support. The whole ceiling was PVA'd and skimmed with Thistle Multi - 6 years on and no sign of cracking, all looks good.

But, at a previous house a previous owner had had the ceilings overboarded. The sheets were fixed in place by what seemed to be random screwing, which of course went mostly into or between the old laths. Joints were put any old where. Needless to say cracking at board joints was a problem. If you do a job as you describe above PP then you'll get problems, but done carefully overboarding can be OK. I'd also recommend the paper type joint tape - where you put some plaster over the joint and then push the paper tape into it to hold it, rather than the much more common self-adhesive mesh type. A very experienced plasterer told me that the paper type is less prone to cracking in the long term.

 

[plasticpigeon]

I can see that overboarding with care as you have done would work well. I am trying to find a quicker easier method as I am getting fed up. I think I will try the scrim out but I will try and get the majority of wallpaper off the ceiling first. If it goes wrong I can always overboard!!!

 

[Zebra]

Pp, don't get fed up and take a short cut! Take a break from it, do something else for a bit, the house won't mind, it'll still be there, patiently waiting. Get your mind off it for a while. At least that's what everyone on here has advised me to do when I've felt overwhelmed and not very stripey. Then when you come back a bit fresher, you'll make a decision you feel is the right one, rather than just the one that gets the job done quickly.
I know you've taken real pains with your house. What you did with the bay window, and your plastering efforts elsewhere. Don't rush it now, and take a short cut which you might regret later. And you don't want to have to do it twice!
I know it all takes ages. Many of us on here are, like myself, four years in to a one year project, or similar. And were it not for this forum I would have given up and taken many shortcuts to get it done quicker, because everyone else around in the "normal" world looks upon taking four years to do up a house as a bit mad. But stay with us pp, we're all just as mad, and your house deserves better.

 

[88v8]

It does take an awful long time to do things properly.
And if you don't intend to stay there for ever, well you already know what the next owner is likely to do with your painstaking efforts.

In our previous house, very cracked/blown plaster, I removed none of it, even though some of the ceilings were quite loose. I used scrim paper to keep it in place. Scrim paper seems to have vanished, but this stuff would likely do the job although I haven't actually looked at any as we have no plaster here
http://www.decorating-supplies.co.uk/epages/BT3825.sf/en_GB/?ObjectPath=/Shops/BT3825/Products/WPREM

And then I'd paper over the top of it, crossways of course, with a 'period' anaglypta.
And paint that.

In our bedroom, which was the worst, I put up two layers of scrim paper, and also scrimmed over the cracks first with 2" paste-on scrim. Was OK 20 years later.

Ceiling papering seems hard at first, but I got good at it. A tee bar to hold up the folded paper, it got so I could paper a 12' run single-handed and get the patterns to match. Have a go.

Ivor

Edit... just got to your thread with the pic. Hmmmm. Well, I'd still leave as much as possible in place.

 

[Zebra]

Have disovered that if you run out of plastering scrim mesh, you can make some out of the plastic string bags that carrots come in.