skimming over protruding screwheads/washers

[jashton]

Hi.
I've just relined a brick party wall with sound insulating PB. It's 15mm PB with a rubber-foam-rubber backing roughly another 15mm thick. To get the best result the boards have to be fitted so that the backing isn't compressed. On an uneven brick wall that means that some areas will get a bit squashed but no big deal. Main problem is that the boards have to be fixed using screws (I've used masonry screws as they're quicker/easier than wall plugs). Often you have to fit a washer to prevent the screw head pulling through. The finished boards are ok but a lot of the screw heads/washers aren't flush. To get them flush would damage the surface of the boards.
So, question is do I skim them, assuming that in certain areas the first coat will run up to but not really cover the washers/screws but then the second coat will. Or do I put a thin bonding coat across the entire wall to smooth everything out and then skim?

 

[DAZB]

Either way will do the job but I'd advise cutting and sticking a small patch of adhesive scrim tape to each offending screw which will help the plaster stay on once dry and limit cracking.

 

[jashton]

Yeah. I've done that. Scrim and filled over each head/washer. Just wasn't sure if a skim coat on its own would do the job. Certainly prefer that option to putting on a scratch coat first.

 

[Richard C]

I'd stick a coat of Bonding on there first & then skim over that.

 

[jashton]

I'd stick a coat of Bonding on there first & then skim over that.

Never done bonding but assume it's straightforward enough. is there any reason why it can't be a very thin coat? Normally it's a pertty thick coat, right? The screws only protrude a couple of mm and there are a couple of dips in the boards that I need to level out but in general I wouldn't need the bonding coat to be more than 2/3mm deep in most areas

 

[Richard C]

Given that you’ve got protruding screw heads (never a good idea), you need to ensure a decent covering over them if you’re going to avoid popping the heads, even with the tape covering. A tight Bonding coat around 3mm will give you a decent cover for the Multi; it’s also softer than Multi & will be more accommodating to future movement although you may still get popping in the future.

When plastering over deeper Artex patterns, I skim over with a tight Bonding coat first & then finish with Multi. You need to do it in one operation & finish with Multi as soon as the Bonding has gone off; if you leave it overnight, you’ll have suction problems & will need to prep it accordingly.

 

[jashton]

Given that you’ve got protruding screw heads (never a good idea), you need to ensure a decent covering over them if you’re going to avoid popping the heads, even with the tape covering. A tight Bonding coat around 3mm will give you a decent cover for the Multi; it’s also softer than Multi & will be more accommodating to future movement although you may still get popping in the future.

When plastering over deeper Artex patterns, I skim over with a tight Bonding coat first & then finish with Multi. You need to do it in one operation & finish with Multi as soon as the Bonding has gone off; if you leave it overnight, you’ll have suction problems & will need to prep it accordingly.

thanks. I'll put a bonding coat on then. My concern is I'm not sure if I'm quick enough to get the bonding plus top coats on in the same day. It's a 4x2.5m wall and I'm pretty slow. Assume if I leave the bonding overnight then will need to give it a dilute PVA coat prior to multi going on?

 

[NickB_99]

thanks. I'll put a bonding coat on then. My concern is I'm not sure if I'm quick enough to get the bonding plus top coats on in the same day. It's a 4x2.5m wall and I'm pretty slow. Assume if I leave the bonding overnight then will need to give it a dilute PVA coat prior to multi going on?

I find a tight Bonding coat quite easy to put on as it has 'coarse granules' in it, which I find help me gauge the thickness. I think from memory they're called vermiculite.

To do both the same day will be better for sure.
When I've put Bonding on at home, next day I've needed some diluted PVA as it was drying out too quick. But that was on top of blocks and it was a thick coat of Bonding. Here you've got plasterboard underneath and only a thin coat, so suction should be less. If you do leave it to next day, maybe wet a part of it before you start skimming, to check to see how much suction there is and whether diluted PVA needed.

 

[stevethespreader]

if you knew your wall was uneven you should have dubbed it out first before you boarded it would have been a lot easier screwing the fixings in, if yor screws are proud it will only be a matter of time before they pop the plaster

 

[Richard C]

My concern is I'm not sure if I'm quick enough to get the bonding plus top coats on in the same day. It's a 4x2.5m wall and I'm pretty slow. Assume if I leave the bonding overnight then will need to give it a dilute PVA coat prior to multi going on?

That doesn’t really make sense Whatever your putting up there has got to be on, trowelled up & finished within around 1 ½ hours or it’ll have gone off on you. By the time you clean up & get ready for the next mix, each session equates to around 2 hours & I aim to get 4 of those in a day, usually enough to skim a complete 4 x 4m room & I can over skim a 24 sq/metre Artex ceiling in 2 x 2 hour sessions, Bonding & Finish; I certainly aint no super spread & consider myself slower than most

Have you done much plastering before? If you’re not confident you can manage that size of wall in one hit, I would advise you call someone in; if you run out of time the chances are it’ll end up looking like a disaster zone

 

[roughcaster]

I'd stick a coat of Bonding on there first & then skim over that.

I'd do it the same way.

 

[peaps]

You could scrim it up with cotton or hessian, the old method..?

 

[stevethespreader]

You could scrim it up with cotton or hessian, the old method..?

 

[Alastairreid]

You could scrim it up with cotton or hessian, the old method..?

Wattle and daub Roughcaster will explain

 

[stevethespreader]

You could scrim it up with cotton or hessian, the old method..?

Wattle and daub Roughcaster will explain

no need to expain anything the smiley was me laughing at numpy nuts who had stated in another post (quote) "Hardly stuck in the past. I apply traditional plastering techniques when needed and moden when needed."
i rest my case