Solid walls breathable water resistant render query

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Paddyduggy

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Hi bought old house with solid walls and old pebbledash on. Renderer thinks too difficult to remove all render which I agree so intending to do primer, basecoat and roughcast top coat over old render. Need to keep walls as breathable as possible to reduce potential damp but also want water resistant from the new render. I have done a bit of research but still not sure What to use, local guy recommended VPI monocal or renopass chaux (more lime version) but When I spray water on samples it's soaks straight in so not water resistant enough. Suggested I could spray or roll on waterproofer afterwards but dont know if this works and twould need to keep doing this every few years So was thinking Of more silicone render maybe K rend or other brands but wanted to know if they are actually water resistant and breathable as it says and able to be spayed on as rough cast. Any advice experience appreciated thanks
 
Paddyduggy said:
Hi bought old house with solid walls and old pebbledash on. Renderer thinks too difficult to remove all render which I agree so intending to do primer, basecoat and roughcast top coat over old render. Need to keep walls as breathable as possible to reduce potential damp but also want water resistant from the new render. I have done a bit of research but still not sure What to use, local guy recommended VPI monocal or renopass chaux (more lime version) but When I spray water on samples it's soaks straight in so not water resistant enough. Suggested I could spray or roll on waterproofer afterwards but dont know if this works and twould need to keep doing this every few years So was thinking Of more silicone render maybe K rend or other brands but wanted to know if they are actually water resistant and breathable as it says and able to be spayed on as rough cast. Any advice experience appreciated thanks
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How can you keep the walls breathable if you’re coating over pebbledash?
 
What age is your house? is it a solid council house which would be a wimpy style house with pebbledash in the concrete panels.

or a.traditional 9inch solid brick.

you may be eligable for a grant under eco plus scheme to install external wall insulation
 
The pebble dash render on now contains lime as I sprayed It with white vinegar and it fizzes more than some some other areas of normal sand cement on the path etc so it's probably sand cement and lime but about 50 years old. I know the existing render will reduce the breathability read but we have tried to hack a bit off and it doesn't come off easy so im stuck with ungortuneately so gonna go over it as i said. i was looking at K1 render basecoat mesh and top coat then spray to give it a light roughcast effect hopefully if any experience of that but just saw k rend do a light weight render so will check that if anyone has experience of that ? or any other brands that are supposed to be breathable? but also want it to be water repellant as k rend says it is thanks
 
Paddyduggy said:
The pebble dash render on now contains lime as I sprayed It with white vinegar and it fizzes more than some some other areas of normal sand cement on the path etc so it's probably sand cement and lime but about 50 years old. I know the existing render will reduce the breathability read but we have tried to hack a bit off and it doesn't come off easy so im stuck with ungortuneately so gonna go over it as i said. i was looking at K1 render basecoat mesh and top coat then spray to give it a light roughcast effect hopefully if any experience of that but just saw k rend do a light weight render so will check that if anyone has experience of that ? or any other brands that are supposed to be breathable? but also want it to be water repellant as k rend says it is thanks
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If you can find him, maybe you can hire @Casper
 
Paddyduggy said:
The pebble dash render on now contains lime as I sprayed It with white vinegar and it fizzes more than some some other areas of normal sand cement on the path etc so it's probably sand cement and lime but about 50 years old. I know the existing render will reduce the breathability read but we have tried to hack a bit off and it doesn't come off easy so im stuck with ungortuneately so gonna go over it as i said. i was looking at K1 render basecoat mesh and top coat then spray to give it a light roughcast effect hopefully if any experience of that but just saw k rend do a light weight render so will check that if anyone has experience of that ? or any other brands that are supposed to be breathable? but also want it to be water repellant as k rend says it is thanks
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No point I pursuing anything breathable.


If your mix currently on there is cement based and you're not removing it - forget breathable - no point.
Even it if has hydrated lime in the mix, cement will kill its breathability.


Most render products are weather resistant not necessarily water repellant.


Is it the repellency you definitely want?

And what is the ideal finish/look you like?
 
Thanks so far Yes it is cement based and just probably put a bit more lime in when it was done so its reduced the breathability as you say but walls are ok inside there was some damp but removed paper and have dried out as mostly original lime plaster so i think breathability of current render probably just about getting away with it but dont want to make it much worse by putting non breathable render on. I know not ideal but am a bit stuck so any experinece of whether k rend k1 is breathable or k rend have a lightweight LW1 version so maybe that or any other manufacturer silicone render would be good?
 
I Want the render to be a bit water repellent at least and I like the look of rough cast but no pebbles in it so it would be sprayed on at the end to give it rough cast look so was thinking k rend k1 but is it really water repellant and breathable but as spitandpolish says maybe it doesn't matter so much breathability as its going over the old pebbledash?
 
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