Re-rendering - what's best?

peweuk · 12 Aug 2010

I have an old single storey extension on the house which used to be the main access to the house. It is about 6 metres long.

Planning have insisted I replace the door with a window as we now have a new front access as part of a new extension.

The old extension has a 'rough' rendered and painted surface (tyrolean??) which is perfectly sound.
I want to smooth it off when I have the new blockwork under the window done.

Do I need to remove the exisitng render first, or can I just score the existing render, add something like PVA and render over the top?
If it is to be removed, do I go all the way back to the block, or just take of the surface with the paint on it.

I have had 2 quotes, and one said 'PVA'. the other said remove. Not sure which way to go.

troweladdict · 12 Aug 2010

you mit be able too prim coat the walls first then scrach coat bead up top off. But id be thinking of the thickness
Id just have it all off back to brick/block then wetthe walls down with a hose then scrach coat it top it of with a lime render
scrach coat 4:1mix water proofer
top coat 5:1:1
sponge finish sorted
id use bell cast beads (white UPVC)
looks nice too

external · 12 Aug 2010

lime and waterpoofter dont work together trowel!

troweladdict · 12 Aug 2010

so you saying all them rendering jobs iv dont are rong then ****** 4/1mix scrach coat and a top coat of sand cement and lime dont go ill get on the phone and call all my custz and tell them

Micilin · 13 Aug 2010

external said:
lime and waterpoofter dont work together trowel!

Spot on, read the label or ring them up.
Edit - in the same mix that is

Micilin · 13 Aug 2010

troweladdict said:
so you saying all them rendering jobs iv dont are rong then **** 4/1mix scrach coat and a top coat of sand cement and lime dont go ill get on the phone and call all my custz and tell them

Nothing wrong with 4:1 scratch with w/p , no lime topped by 5:1:1 .

Putting lime in with w/p in the same mix is different . It won't fall off, it's just that you've not got any benefit from the waterproofer apart from it making the mix nicer to use.

Micilin · 13 Aug 2010

peweuk said:
Do I need to remove the exisitng render first, or can I just score the existing render, add something like PVA and render over the top?
If it is to be removed, do I go all the way back to the block, or just take of the surface with the paint on it.

I have had 2 quotes, and one said 'PVA'. the other said remove. Not sure which way to go.

As said above, if you can remove it, then that is better.

If going over it, which is fine if it is sound -

Stay away from PVa outside, use SBR instead - but just painting it on is no good, adding it to the render mix is no good.

You need SBR slurry, rendaid or similar from Krend put on first to stick to teh existing and give you a key.

A 'sparrowpeck' all over with a scutch hammer or the clayw of a hammer first will improve the key and you can check for live spot as you go.

Stay clear of the guy who suggested PVA.

peweuk · 13 Aug 2010

Sorry, my mistake - he did say 'SBR, which works like PVA' - but I couldn't remember what he said.

Looks like the best solution is to strip it. Not nice

, but it is only a small area

Thanks guys.

troweladdict · 13 Aug 2010

water proofer in the scrach coat not in the top coat with the lime numty its a two coat thing
let the scrach dry over night then top it off
as it helps stop the top pall in too quick and helps water proof it a bit till its sealed

external · 13 Aug 2010

trowel my friend i've made more mistakes than you've got things right,if i told you i've renderd a thousand houses id be selling myself short,lime and w/p cancel each other out,dont no why im not a chemist but its the way of the world,learn by my mistakes my friend

troweladdict · 13 Aug 2010

ok well said m8 its just the way i was taught m8 thats all it never gone ronge for me once but ill take on board what you said m8 thanks

external · 13 Aug 2010

nice one m8,only here to help

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Re-rendering - what's best?

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