Renovating external render

[gravelld]

TL;DR: scroll down to "So my questions are about the render" or if you fancy a read about the context...

 

We have a fully rendered house. The render is about 15 years old in its newest spots, maybe 20-25 years old elsewhere. The render is sand and cement. The problems with this are:

• It has popped (taps hollow) in the more exposed locations
• Rusted corner beads
• There are cracks everywhere
• Signs of water ingress in some of the worst places
• Numerous bits crumbling away around the bead at DPC level

 

My original plan was to install EWI at the same time as also replacing the windows (which are also in a bad state of repair).

 

The trouble with this is the cost. Not only in terms of the EWI, but in terms of what the EWI has a knock-on effect on. For example:

• Making sure EWI meets loft insulation
• Digging, parging, insulating below DPC
• Moving drains
• Bricking up windows that are overlapped by insulation
• Converting lean-to roofs to warm roofs.
• Moving the electricity meter
• Changing other services running in and out
• Probably replacing rainwater goods
• Probably replacing soffits/fascias

 

I definitely intend to install EWI in the future. The reality for most people though is that this is extremely expensive.

 

So I wondered what my other options were, and if I can make this project much financially tolerable for my family.

 

Here's what I know I can do to plan for the future:

• Follow details to allow new windows to be moved into the insulation layer later
• Get the cavities fully filled (currently crap partial fill - will source some sort of foam... or something)
• If I have a lower initial project cost, I can spend a little more on quality for what I am actually buying, e.g. window quality

 

If I were to not install EWI and just fix the render, I would want at least a decade, I would hope, to save for EWI with ideally NO maintenance in that time period.

 

So my questions are about the render:

• Is there much point in "patching up" S&C render? What should I fill the removed sections of render with? Won't other areas go, or crack at the join between the two?
• Is it better to rip the lot off and start over with a modern render, e.g. silicone?
• Could we render over the top of the existing render? (This would reduce the space for insulation later if we also don't convert the roof to a warm roof at the same time).

 

Would really appreciate people's knowledge on this one...

 

Edited May 3, 2018 by gravelld

[nod]

9 minutes ago, gravelld said:

TL;DR: scroll down to "So my questions are about the render" or if you fancy a read about the context...

 

We have a fully rendered house. The render is sand and cement. The problems with this are:

• It has popped (taps hollow) in the more exposed locations
• Rusted corner beads
• There are cracks everywhere
• Signs of water ingress in some of the worst places
• Numerous bits crumbling away around the bead at DPC level

 

My original plan was to install EWI at the same time as also replacing the windows (which are also in a bad state of repair).

 

The trouble with this is the cost. Not only in terms of the EWI, but in terms of what the EWI has a knock-on effect on. For example:

• Making sure EWI meets loft insulation
• Digging, parging, insulating below DPC
• Moving drains
• Bricking up windows that are overlapped by insulation
• Converting lean-to roofs to warm roofs.
• Moving the electricity meter
• Changing other services running in and out
• Probably replacing rainwater goods
• Probably replacing soffits/fascias

 

I definitely intend to install EWI in the future. The reality for most people though is that this is extremely expensive.

 

So I wondered what my other options were, and if I can make this project much financially tolerable for my family.

 

Here's what I know I can do to plan for the future:

• Follow details to allow new windows to be moved into the insulation layer later
• Get the cavities fully filled (currently crap partial fill - will source some sort of foam... or something)
• If I have a lower initial project cost, I can spend a little more on quality for what I am actually buying, e.g. window quality

 

If I were to not install EWI and just fix the render, I would want at least a decade, I would hope, to save for EWI with ideally NO maintenance in that time period.

 

So my questions are about the render:

• Is there much point in "patching up" S&C render? What should I fill the removed sections of render with? Won't other areas go, or crack at the join between the two?
• Is it better to rip the lot off and start over with a modern render, e.g. silicone?
• Could we render over the top of the existing render? (This would reduce the space for insulation later if we also don't convert the roof to a warm roof at the same time).

 

Would really appreciate people's knowledge on this one...

 

Knock the lot off

You would be wasting your money patching it up

Sorry

[gravelld]

Don't be sorry, I want honest opinion not sympathy

 

Guide m² price for just a silicone render, no insulation? I'm guessing around £90-100/m² for EWI.

 

Can it be rendered over the top to reduce the labour in knocking the existing good bits off?

Edited May 3, 2018 by gravelld

[Declan52]

Have you figured out why its going boast??

Did they put on a scratch coat first??

Was both the blocks soaked and if it was done the scratch coat soaked prior to doing the top coat??

Was the cement dead maybe??

Was the mix correct??

Was it put on on a real hot day so it dries out before it goes off??

Doubt there is any point in patching it. It needs chipped of and done right.

[Lesgrandepotato]

We rendered over some of ours, but that’s only because it wouldn’t come off without taking half the blocks with it. 

 

I think I’d be wondering if Ewi is actually worth it on this property. Can’t polish a t**d. Is Ewi just rolling it in glitter?

[gravelld]

@Declan52 this is old render, not a new job... is that what you thought I meant?
 

[gravelld]

3 minutes ago, Lesgrandepotato said:

I think I’d be wondering if Ewi is actually worth it on this property. Can’t polish a t**d. Is Ewi just rolling it in glitter?

 

Don't understand this reasoning but I love the analogy  Can you explain?

[nod]

I normally tell custermers If it’s to hard to knock off it’s ok to go over it But that’s useally when the top coat has shelled off leaving a rock hard base coat 

In any case you will need a scratch coat with reinforced fibre mesh troweled into it To stop the same thing happening again and to help cope with the suction

 

I suspect that the galvanised beads are the culprits They are real water magnets The was a spell when mainstream builders were allowing them to be used 

 

I rendered a house thirty five years ago near were we live 

I didn’t use any beads Looks as sharp as the day it was done 

 

[Lesgrandepotato]

My thinking is as follows EWI is quite a challenging project for the house and a major investment. 

 

Could you achieve 80% of the gain for 20% effort with internal insulation? We didn’t Ewi even though we re rendered the entire building as my feeling was that it still wouldn’t be that efficient and we could create a better effect with 60mm of celotex around all the internal walls.

 

You could then go room by room? And the disruption is much lower. 

 

[Declan52]

47 minutes ago, gravelld said:

@Declan52 this is old render, not a new job... is that what you thought I meant?
 

Yeah thought it was only put on.

[gravelld]

 

22 minutes ago, nod said:

In any case you will need a scratch coat with reinforced fibre mesh troweled into it To stop the same thing happening again and to help cope with the suction

 

What's the minimum overhang from verges on gables? If we go over the top of the existing render, require a scratch coat and then a finish it might push out too far...

 

Do you still have a scratch coat for silicone render? For example this has polymer render, primer, then silicone render: https://alumascfacades.com/product/silkolitt-solo/ .Does the scratch coat do the same thing as the scrim and base coat in an EWI build up? 

 

Sorry for the questions, I just want to understand as much as I can.

 

22 minutes ago, nod said:

I suspect that the galvanised beads are the culprits They are real water magnets The was a spell when mainstream builders were allowing them to be used 

 

In the places with the worst popping there actually isn't any rusting, however there are signs of water ingress (I didn't spot it, an EWI surveyor did) in the same area. So maybe that caused it.

 

The rusting is actually on the newest parts of rendering, early 2000s extension.

 

22 minutes ago, nod said:

I didn’t use any beads Looks as sharp as the day it was done 

 

Want a job?  

[PeterW]

Just now, gravelld said:

The rusting is actually on the newest parts of rendering, early 2000s extension.

 

Usually down to cheap beads. Older ones were heavier with more galv so kept their coating better when scratched. They have got thinner and thinner over time to keep cost down. 

[gravelld]

10 minutes ago, Lesgrandepotato said:

My thinking is as follows EWI is quite a challenging project for the house and a major investment. 

 

Could you achieve 80% of the gain for 20% effort with internal insulation? We didn’t Ewi even though we re rendered the entire building as my feeling was that it still wouldn’t be that efficient and we could create a better effect with 60mm of celotex around all the internal walls.

 

You could then go room by room? And the disruption is much lower. 

 

For sure. I have to admit part of my motivation is the extra complexity. Look at the list above - so much to think about.

 

I'm next to 100% sure EWI is the best way long term, but to minimise the normal risks of IWI but also because this house can take it in terms of being detached, plenty of space, plenty of thermal capacity to use etc.

 

I'm not 100% sure about sticky block EWI systems, but that's off topic and for another thread.

[gravelld]

1 minute ago, PeterW said:

 

Usually down to cheap beads. Older ones were heavier with more galv so kept their coating better when scratched. They have got thinner and thinner over time to keep cost down. 

 

What would you do [about the render] @PeterW ?

[PeterW]

Like @nod says - off with the lot and start again...

 

Polymer render is  thinner too in a lot of cases so you need a decent base to work from and a mess of renders isn’t what you want. 

 

How old is the main house ..?

[nod]

4 minutes ago, gravelld said:

 

 

What's the minimum overhang from verges on gables? If we go over the top of the existing render, require a scratch coat and then a finish it might push out too far...

 

Do you still have a scratch coat for silicone render? For example this has polymer render, primer, then silicone render: https://alumascfacades.com/product/silkolitt-solo/ .Does the scratch coat do the same thing as the scrim and base coat in an EWI build up? 

 

Sorry for the questions, I just want to understand as much as I can.

 

 

In the places with the worst popping there actually isn't any rusting, however there are signs of water ingress (I didn't spot it, an EWI surveyor did) in the same area. So maybe that caused it.

 

The rusting is actually on the newest parts of rendering, early 2000s extension.

 

 

Want a job?  

You will always need a 5 mil base coat on most surfaces other than concrete blocks 

 

[gravelld]

21 minutes ago, PeterW said:

Polymer render is  thinner too in a lot of cases so you need a decent base to work from and a mess of renders isn’t what you want. 

 

Sorry - can you explain that?

 

Why does it matter if it's thinner? If we're taking everything off anyway, shouldn't we follow whatever the "system" says?

 

21 minutes ago, PeterW said:

 

How old is the main house ..?

 

1950s originally, extensions done in 80s, 90s and 00s.

 

 

[PeterW]

Sorry - meant that you want to take it all off, not just bits and try and put a polymer over the top of a variety of base coats

[Declan52]

1 hour ago, nod said:

 

 

I didn’t use any beads Looks as sharp as the day it was done 

 

Made sure there where no beads on my outside render. Just used lengths of 4*1 skirting with a chamfered edge and lath to form the edges and bottoms. 

[nod]

7 minutes ago, Declan52 said:

Made sure there where no beads on my outside render. Just used lengths of 4*1 skirting with a chamfered edge and lath to form the edges and bottoms. 

Old school

Never get water and frost behind it 

[Declan52]

25 minutes ago, nod said:

Old school

Never get water and frost behind it 

Plenty of medusa in the mix so should be fine.

[nod]

1 hour ago, Declan52 said:

Plenty of medusa in the mix so should be fine.

Do you know Declan 

I get jobs to price With alsorts of exspensive adetives specified

Meduca mixed into dry cement is totally waterproof and cheap as chips But nowone every asked for it The exspensive  stuff must be better 

It comes in a shiny container 

[gravelld]

So @nod are you saying S&C can be good enough if correctly installed for at least a decade or so?

 

Or play it safe with a silicone render?

 

Is there such a thing as a typical price range per m2 for just rendering?

[nod]

3 hours ago, gravelld said:

So @nod are you saying S&C can be good enough if correctly installed for at least a decade or so?

 

Or play it safe with a silicone render?

 

Is there such a thing as a typical price range per m2 for just rendering?

Yes if it’s rock hard you can go over it

[Ed_MK]

I am in a similar positions ....albeit I dont have anything to knock off

as its a new build Timber frame ...

 

I have had a few quotes from Good Old S+C (which some still say is fantastic)

to all these new sexy self coloured silicons that you jetwash and some other stuff too ...

confused? ...ohhhhh yes (as the Churchill Dog says)

 

I keep going over and over the elevations in an old auto-cad ...and i can't seem to get over how the 
sq meterage is soo high ....when you add it all up (see below)

 

with the prices you quoted above ...I am hoping I can chip a bit ...or else my house will be "bare-arsed" for a few months.

although I could get used to that Silver Potton Insulation look ......kind of Space age