External stone rendering

[Jmcl101]

Got a big old farmhouse to do. The main dwelling is made of stone/Flint with some new build extensions being done in sand and cement..

I'm assuming the following is best for the stonework walls -

1)Scat coat 3:1 nhl mix coarse sand
2) Mesh/scratch coat to fill out 3:1 nhl plastering sand
3) ruled off topcoat rubbed up wth a float and a sponge. 3:1 plastering sand nhl

I'm assuming 3-4 days between coats and covering everything up/wetting down before coats as usual.

Does this sound about right for the substrate ? Should we use fine sand for topcoat ?

Any tips and advice would be appreciated, been a plasterer a long time now but only limited nhl experience.

 

[Jerseyboy]

Got a big old farmhouse to do. The main dwelling is made of stone/Flint with some new build extensions being done in sand and cement..

I'm assuming the following is best for the stonework walls -

1)Scat coat 3:1 nhl mix coarse sand
2) Mesh/scratch coat to fill out 3:1 nhl plastering sand
3) ruled off topcoat rubbed up wth a float and a sponge. 3:1 plastering sand nhl

I'm assuming 3-4 days between coats and covering everything up/wetting down before coats as usual.

Does this sound about right for the substrate ? Should we use fine sand for topcoat ?

Any tips and advice would be appreciated, been a plasterer a long time now but only limited nhl experience.

If I was going over stone I would scud the walls with 2+1 with Sbr
Then I would build out any holes or hollows with a stiff 3+1
After a couple of days scratch coat with 3+1 and if it needs a second scratch
Use a 4 +1 with 4 days between each coat.
My final coat would be 6 sand 1 cement and half a lime
And freeflo in every coat.

 

[theclemo]

As above

 

[Jmcl101]

So cement is OK even though it's stone ?

What about the moisture sweating through the walls inside ? (They're dry at the moment and stone is in good nick, but I've heard horror stories)

Did a stone barn in sand and cement 5 years ago and that's been fine. No cracks whatsoever but we used Polymesh in the scratch and lots of hydralime

 

[Fatarm]

Did a stone barn in sand and cement 5 years ago and that's been fine. No cracks whatsoever but we used Polymesh in the scratch and lots of hydralime

Do the same again then??

 

[Jmcl101]

Well I had taken some advice from an old boy who does a bit for me. Wondered if there was more wise-advice here from someone with lots of experience with stone.

Would you like some ketchup with that ?

 

[Jerseyboy]

If it ain't broke don't try to fix it.
If your worried why don't you just use traditional lime and horse hair it worked for hundreds of years

 

[User___removed]

All the lime experts will say you need to use a breathable lime render as there's no cavity and the walls can't breath
They will say sand & cement will fail

 

[User___removed]

If I was going over stone I would scud the walls with 2+1 with Sbr
Then I would build out any holes or hollows with a stiff 3+1
After a couple of days scratch coat with 3+1 and if it needs a second scratch
Use a 4 +1 with 4 days between each coat.
My final coat would be 6 sand 1 cement and half a lime
And freeflo in every coat.

Sounds good although the backing coats seem to strong a mix
I use 6/1/1 for top coat when using site mix with a slightly lesser mix for backing coats
The more lime in all coats the better

 

[Jerseyboy]

Sounds good although the backing coats seem to strong a mix
I use 6/1/1 for top coat when using site mix with a slightly lesser mix for backing coats
The more lime in all coats the better

Sounds good although the backing coats seem to strong a mix
I use 6/1/1 for top coat when using site mix with a slightly lesser mix for backing coats
The more lime in all coats the better

i use 3+1 because I use blue circle 32n
But 4+1 would be ok also I only use lime in the scratch coat in winter because it pulls in to much in the warm weather

 

[hail hail]

Don't cover it all up because its a sin in my book. Here's a cottage I skiimed out just before xmass, talked the guy into keeping some walls instead of covering them. Done myself out of a few walls but like to see cottages with some exposed stone so didn't give a fcuk about the money.


Pics are before sand blasted and also the doorframe covered in skim was getting renewed with walnut in case yas think I'm a hallion with skim all over it

 

[flynnyman]

Rule of thumb don't be going over with something stronger than substrate

 

[Jerseyboy]

Rule of thumb don't be going over with something stronger than substrate

Yes I was always told never put a strong man on a weak mans back!!

 

[vfr12]

snowboard size trowel leaning on the wall next to the window? I want one like this @Rossi46

 

[adapt]

Your mixes are way too strong on stone work, we use about 5 to 1 on our work. A lot of our work is stone houses and I have seen guys who cannot do it because they are too use to brick and tight coats.
We sometimes have to put 3+ inch on walls and the best way we do it is to do all your scratching out with building sand then top coat with plastering sand. Also try not to work it too early on the scratches throw it on and leave it for an hour at least. Also lash a bit of plastersizer & SBR in the mix.