Rotten plaster - dryline? skim? batten? insulate? Confusion!

[Russtavo]

Hi all,

Just bought our first house - a 1930's semi - in need of renovation. A lot of the (original) plaster is crumbling off in quite a few places - see pic below of gable end wall.

There doesn't appear to be any damp issues in the house (touch wood), the plaster seems dry enough - just old, thick and crumbly. When I read about plasterboard/skim vs wet plastering, dot & dab vs battening, not to mention the various insulating products, I find it confusing. What do you folks recommend going forward?

FYI, the house has cavity walls (not insulated) and I've just had remedial wall ties fitted to external walls. Thanks all

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[PrenticeBoyofDerry]

It's personal choice if you want the work doing fast, have it plastered.
Is it an optical illusion, where are the stairs going

 

[Richard C]

A personal view but for me it has to be a proper plaster job; float & set render base followed by finish skim. As it’s a cavity wall & there appears no sign of damp ingress you don’t really need to worry about battening if you want to use plasterboard & skim, just dot & dab it on there; but please skim it, don’t just tape & fill. If you want to raise the thermal insulation a little, one insulation boards might be a better bet;
http://www.british-gypsum.com/produ...s/gyproc_thermal/gyproc_thermaline_basic.aspx
but you will loose a some space depending on the thickness of insulation you chose; IMO insulating the cavity is far better.

Something to watch out for; be aware that removing more than 24% of the plaster/render from external walls exceeds the Building Regulation definition of minor work to a thermal element. If you’re having any other notifyable work done that needs inspecting & your LABC inspector spots it (even on an unrelated visit) he may insist the insulation is brought up to current regulation standards; no problem if you intended that anyway but could be expensive if you didn’t; & its notifyable work!

 

[Russtavo]

Thanks for the very informative post Richard, a few furthers Qs if I may.

Just out of interest, why do you prefer float & set rather than dot & dab?

I'd like to reduce heat loss but in terms of insulated plasterboards, there are quite a few products out there, with prices varying considerably (The Gypsum you mentioned, Kingspan, Celotex, etc). What would give me the most "bang for my buck"?

Finally, you believe insulating the cavity is superior - but could this in itself cause damp problems? I refer you to these pages:

http://www.housebuildersupdate.co.uk/2005/11/on-cavity-wall-insulation.html
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=967

Many thanks!

Russ

 

[Richard C]

Just out of interest, why do you prefer float & set rather than dot & dab?

It’s the traditional way of finishing internal brick walls & is still the finish you will find in new properties of any quality; it’s also a much more hardwearing finish. Plasterboard dry lining/skimming has its uses particularly on internal stud walls but the large estate builders & many renovators use it because it’s cheaper & quicker to install & maximises profit; you don’t need anywhere near as much skill to skim over boards.

I'd like to reduce heat loss but in terms of insulated plasterboards, there are quite a few products out there, with prices varying considerably (The Gypsum you mentioned, Kingspan, Celotex, etc). What would give me the most "bang for my buck"?

I tend to use British Gypsum products as they are easily available in my area. Personally I have no idea how the individual products compare in terms of value but there probably isn’t much difference in technical specification if you compare like for like.

Finally, you believe insulating the cavity is superior - but could this in itself cause damp problems? I refer you to these pages:
http://www.housebuildersupdate.co.uk/2005/11/on-cavity-wall-insulation.html
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=967

Filling a cavity with insulation (if you have one) is less obtrusive & more cost effective (particularly with the grants available) than sticking it on the inside or outside walls. I’m no expert on after market cavity insulation but I don’t think there is any question it will increase thermal insulation but it can lead to other problems if it’s not done correctly or cheap/inappropriate materials are used. There are mixed views; my near neighbour had it installed 4 years ago swears by it & has had no problems but others I spoken to tell me to avoid it like the plague. Personally I haven’t done any research & have yet to decided one way or the other so, for the time being, my original cavities remain empty.

 

[spongey]

i would also prefer the float and set method as rc suggests, it is a longer process but imo gives a superior longer lasting surface.

if you are worried about the thermal properties of sand and cement v's plasterboard's then why not use a renovating plaster over a waterproof scratch coat?

i use a product when damp proofing that is breathable, resists salt ingress and has good thermal qualities.

 

[joe-90]

Personally I'd dot and dab with 12.5 plasterboard. I see some horrendous float and set jobs and it looks like your walls have the light shining down them so the ripples will stand out like anything. Then you get into an argument with the plasterer about whether that is acceptable or not etc etc.

Even a basic plasterer can get decent results with plasterboard and it will be way cheaper (and more insulating).

 

[spongey]

In a nut shell dot and dab is faster and you can get reasonable results yourself.

if you are getting a spread to do it then my personal preference would be sand and cement because it is more durable.

if your spread leaves it anything other flat flat and smooth then dont pay him!! i wouldn't expect anything less if i did that.

 

[joe-90]

That would be my preference if I knew I would get a proper job, but it's risky and it would cost about twice as much. Sand/cement is also very cold.

 

[Russtavo]

Thanks to all for replying in this thread. I think Spongey's idea for renovating plaster is the best one for the inner cavity walls, then dot and dab for any other interior walls. Spongey, what product do you use?

My concern with sand/cement is that it's not breatheable.