Conflicting Plastering Advice

oxygen_old

Hey. Im getting wildly conflicting advice from several plasterers, which is driving me nuts. Basically, I recently got a house rewired, so its chased and what not. It was an old house, maybe 60's. There was at some stage a decent plastering job on it, but there are maybe 5 layers of paint on it since then, with various parts flaking here and there.

Also Im looking to get it drylined with the new sei grant. Just the external walls (inside of the house.)

So to some of the conflicting advice Ive gotten (on the internal walls, not the external insulated walls).

-I cant polybond and scim over the existing walls, because it will bubble when painted.

Is this true, I dont really want to add a half inch plasterboard slab to each wall, I think that the drywall slabing is for timber frames, not to be sticking onto an existing plastered solid wall, as a cure all.


-They can sand down the existing wall, even it out, stanly knife the wall (I forget what he called that part), polybond, fill in any holes or chasing, and scim onto that

Is this doable, I like the sound of it, easiest, and I hope cheapest.

-I could use something called thinsle bond on the wall which will stick to the wall very well.

Has anyone heard of this? apparently it has a texture of paint mixed with sand, and dries bright green. I like the sound of it, but have never heard of it before.


Also, does anyone know the accepted width of the insulation slab, some plasters have been saying an inch and a half, which I can live with loosing off each wall should be fine. But one plasterer said it would be minimum 4 inches, and that it will need an air cavity to stop dry rot? This was news to me.

Thanks allot for any replies

northdublin

i re-slabbed my whole house, i fixed the plaster board directly to the wall using mushroom fixings, then scrim taped the joints and got it skimmed.
ive had no problems and was easier and cheaper then putting up a load of battons first.

PeteHeat

Hi oxygen,

A lot depends on what they are looking at, walls that were chased and have conduit in the chases are easy enough to repair.

Fill out the chases with bonding, a good plasterer will have no problem keeping the undercoat (bonding) behind the existing finish leaving room for the final skim coat feathered into the the existing finish.

If there are a lot of chases on the internal walls I would suggest bonding and fixing 10mm plaster board and skim coat purely on the basis that is less labour intensive (faster) and easier to get a nice finish.

On the extenal walls you have a few choices especially to upgrade the insulation level, fixing a slab direct to the wall will get you a nice finish but no insulation value.

There are pre-insulated plaster boards available up to approx 60mm thickness that can be fixed to the walls and skimmed, another option especially if there are signs of damp or condensation is to lath the walls and fix the insulated plaster board to the laths.

Thistle is just another name for a type of bonding nothing extra special about it.

The above are just options I can't say which is best without looking at the walls, both inside and outside.

I hope the above is of some help.

.

oxygen_old

thanks for that PeteHeat. Some good advice. I have the plasterer measuring up today, and Im going to meet him then to discuss my options. Im probably going to go with the insulation on the external walls, the sei grant is too good to turn down.

Good to know that about thisle, no revolutionary product there then. Just in terms of the internal walls, if he tells me he can skim onto them, fine, if not, I'll just go with the 10mm thickness plaster board. Attaching to the laths isnt really an option for me unfortunatly, as all my walls are solid brick.

Carlow52

northdublin wrote: »

i re-slabbed my whole house, i fixed the plaster board directly to the wall using mushroom fixings, then scrim taped the joints and got it skimmed.
ive had no problems and was easier and cheaper then putting up a load of battons first.

Yes, undoubtedly <was easier and cheaper then putting up a load of battons first> but it is very misleading to imply here that putting up battens offers no improvement over what you did for the additional expense.

It not like with like.

oxygen_old

Yea,Im leaning against putting battons up. Im dont want to loose any more space from each room

northdublin

Carlow52 wrote: »

Yes, undoubtedly <was easier and cheaper then putting up a load of battons first> but it is very misleading to imply here that putting up battens offers no improvement over what you did for the additional expense.

It not like with like.

i would be of the opinion that both methods give similar results with respect to finished result, ie a nice even surface easilly skimmed without the prep work that comes with bonding chases and skimming onto an uneven wall.
i dont see in my post where i implied that the method i used was of an improvement over using battons. ive used both methods but prefere the using the mushrooms especially when using insulated boards for the two reasons i stated, and i could think of about 10 other reasons but chose to keep my post short.

Carlow52

ND: u wrote originally:

i re-slabbed my whole house, i fixed the plaster board directly to the wall using mushroom fixings, then scrim taped the joints and got it skimmed.
ive had no problems and was easier and cheaper then putting up a load of battons first.

The crunch line in the OP's post was:

So to some of the conflicting advice Ive gotten (on the internal walls, not the external insulated walls).

This is the issue I addressed. You make no reference to chasing etc.

As a counterpoint to the 10 reasons u could not be bothered listing as to why no battens were better: battens on internal walls allow for services such as elec/ alarm/CH pipes etc to be added with no chasing: in particular it allows for radiator pipes to come out of wall and not up through floor.
From a time and cost perspective, there is not much difference between the two.

Finally, for the benefit of other readers, the consensus seems to be that if u are dry-lining an external wall that does not have a cavity wall construction, ie hollow block or solid, it is better to batten: this was not asked by the OP but I have added it for completeness

northdublin

ive yet to see why you think that i feel one method is better then another.
my original post is only a statment of what i done and two of the reasons, i think it futile to start listing off every eventuallity without ever have seeing the job. you seem determined to lead me into some sort of a debate over which method is better when i have made it clear that i think that each has its place and which one is used depends on the job and what the customer wants. each method has advantages and disadvantages but listing them off in an online tennis match serves no purpose. how do you know the walls are not allready chased or the op has underfloor heating and doesnt need chases for pipes to come out of the wall. maybe you have been to this site and have knowledge that i dont but i find it difficult to see how anyone can give such comprehensive advice over a forum when there are so many factors involved.

northdublin

to bring up the op's original post as regards the option of removing the paint and skimming the existing wall. this can be tedious and messy work. if its the type of internal wall im thinking off its a block wall which has a cement render and then a final plaster skim. i have found that its sometimes easier to remove everything down as far as the cement render. again depending on the wall and its condition, the plaster might come off easier then the paint and usually depends on the moisture its received over the last 50 years. scoring with a stanley and polybonding is done in this case to seal the wall but at the same time to give a surface the new skimcoat can adhere to. ive done this in the past a few times and found the type of wide long handled scrapers with the changable baldes that decorators use to be the best to remove this material.

oxygen_old

yea, I'm getting a good few plasters saying that they cant remove the layers of paint and bring it back to the brick work. I would have thought there were machines to do that.

In any case, will all the chasing, after its filled in I think it will need to be plasterboarded anyway

PeteHeat

Hi,

I think northdublin posted in good faith, if I want to get a smooth finish over a difficult / costly to prepare base I would have no problem using his system in fact I have used it.

I posted because based on professional experience (not a plasterer) I thought there were a few options more suited to the original question, I think all of the replies are useful depending on the job at hand.

Oxygen,

I wouldn't rule out laths because of the brick work, in fact I would suggest that you double check the walls outside, if there are any signs of loose pointing etc I would use the laths as another job they do is allow air to circulate in the space between the wall and the insulated board preventing modest amounts of moisture and condensation from damaging new insulation and finished surface.

Best of luck with the renovation.

.

Spread

Dub out the chases. Apply 5:1 (water : PVA). When dry apply 3:1 and skim while still tacky. While you are at it insulate the external walls first.

John Mason

hey

i had a similar problem in my house and thistlebonded all the walls and ceilings. my walls and ceilings had a stippled effect

its a messy but fun job.

that was 4 years ago and i never had any problems. i used thistle bond which is red and some other type of thistlebond which was green, the green one was better, cant for the life of me think of the name of it.