Sealing sandstone internally

[Johnboy54]

Hello to all.
I'm still researching!
Internal walls have been stripped of plaster completely. (Solid sandstone)
I now need to rake out the 100 year old 'powder' between the joints.
Then I want to seal all the surfaces so the next stages stick to them.
I then need to repoint these big gaps.
Then I want to plaster/scrim/scratchcoat? with a good waterproof additive included.
Then its the Celotex with plasterboard dot and dabbed to it.
The architect says I can do this, but failed to tell me how.
Celotex techy dept says I can't?
Any thoughts?
Thanks.
John

 

[trowelmonkey1]

Hi John,

Why are you dotting and dabbing boards when you're having the plasterwork re-done?

Celotex PL3000 IS suitable for dot n dab according their website so not sure why they are telling you it isn't.

Regarding the wall you'd better wait for someone else on that but could use stabilising solution then render it?

 

[Johnboy54]

Hello trowelmonkey1.
Celotex say it's not possible to seal sandstone.
Therefore, I can't use their product to dot and dab it.
The architect says I can.
I'm not plastering it because I can't plaster, but can dot and dab.
So, I'll divide the walls into 2 feet sections with battens and render/scrim??? alternate ones, scraping the excess off between the battens. Then remove the battens and fill the sections between.
Because the walls don't have insulation, I wanted to then use the Celotex plasterboards to dot and dab a decent finish.
Are you saying some kind of stabilising solution would prepare the wall prior to pointing and rendering etc?
Would this solution be sprayable because I've a hell of a lot of walls to prepare!
Thanks for the reply.
John

 

[trowelmonkey1]

just an idea, as you're going to the effort of fixing battens to the wall why not go the extra and stud it? that way you can use standard plasterboard and insulate between the studs.

 

[Johnboy54]

Thanks for the suggestion.
Trouble is, I only saw the house once a few weeks ago, and didn't get much chance to check everything.
I asked a similar question at the time about sandstone.
Yesterday, I got to have a better look -(we get the keys tomorrow)
The surface of the exposed sandstone walls are so uneven that I don't think I could batten it to an acceptable standard.
It looks easier to put temporary battens on and continue as I said before.
It's the additives for sealing prior and during I'm really asking about.
John

 

[trowelmonkey1]

have to be honest say the question about sealing/priming sandstone is out of my remit but would love to know the answer from someone else in case i too come up against the problem.

having said that a solution could be to fix EML to the wall wall and plaster that.

 

[Johnboy54]

Looked at the cost of EML..... hell fire!
However, finally got some extra money together to ask architect.
This should be of interest to anyone with the same problem, as nobody seems to know the answer -
Plain and simple waterproof PVA to prime the sandstone.
Sorted.

 

[trowelmonkey1]

neat i pressume

 

[Johnboy54]

3 to 1 he says.

 

[RobinClay]

These messages linger on, worse than garlic !

WELL ????

What did you do, and did it work ????

An Architect can give "advice", but, face it, he is NO expert !

He's (almost always) NEVER actually got his hands dirty !

 

[roy c]

I haven't had much to do with sandstone but I would think that you could put a scratch straight on to it . That would be good enough to dot and dab on then.. I can understand wanting to up the thermal value, but could you not just float and set it?

 

[Micilin]

Even if he is happy to go rendering the sandstone, I can't imagine the architect has much idea about it's application .

To give a proper key, I'd scud the walls with a mix of sandpc:waterproof pva (or preferably SBR)

We used to render onto sandstone in cellars when tanking, and that was a Sika sand and cement 4 coat - scud, coat, scud, coat (rubbed up , no skim ever)

We should know by now what works if he did it last may!

 

[RobinClay]

In his original posting -

Hello to all.
I now need to rake out the 100 year old 'powder' between the joints.

... and that worried me slightly....

That "powder" is lime mortar, which (a) moves with the seasons, and (b) over l o n g periods of time, it settles. If he puts "strong" OPC stuff onto it, over time that wll crack and separate, as the sandstone moves behind it.

Strickly.... he should ONLY use a similar LIME mortar. IF he CBA...

We should know by now what works if he did it last may!

Well, Quite ! That's why I asked....

WELL ???? What did you do, and did it work ????

But he's obviously gorn orff to fresh fields and pastures new....

<grin>

 

[roy c]

I never even looked at the date posted

 

[Johnboy54]

Hello!!
Anybody still there?
I did a mixture.
I've put studs on one wall.
I;ve dot and dabbed directly on a couple of walls that won't be seen because of cupboards.
I've used pva on some others and then dot and dabbed.
12 months later no problems.
I'm a one man band which is why it's taken so long.
I know.
Ask me again in 10 years.
Thanks for all the detailed advice.

John