Lime rendering

[fobos8]

Hi guys

Got a job coming up which is a blockwork bbq/party/summer house with large oak lintels to frame some large open openings. It is single skin blockwork laid on flat.

The customer wants to use a lime render as they have found one that has a lot of course sand in which will look good with the oak beams. The render is Natural Hydraulic Lime 3.5 which contains 85% lime and 15% white cement. Both inner and outer wall will have the lime render.

As the know one problem with lime render is that it is porous and they are worried about damp tracking though the lime render, blockwork and then showing up internally. They've looked at acrylic and silicone renders but there's nothing they like.

The manufacturer has advised against sealing the lime render on the outside.

Anyone got some suggestions about what to do?

Have thought about applying a tanking slurry to the inner wall and then rendering over them but maybe the best solution would be to apply some sort of waterproofing to the exterior walls before applying the lime render - this would stop the water ingress at source.

Have though about a SBR slurry to external walls, let it go tacky and then Lime render over that.

All the best Andrew

 

[vfr12]

it's Halloween, not April the first

 

[fobos8]

any proper suggestions?

 

[Arti]

@raggles

 

[raggles]

The whole thing just sounds like utter bollox. Just find a coarse sand and mix it with white cement and lime on your top coat. If they don't like that idea walk away. Your on a hiding to nowt if you go the lime render route.

 

[fobos8]

thanks raggles - that sounds like a good idea. If I slurry the blockwork with sbr and put sbr in scratch coat too will that help keep the water out or would it be better off just applying a clear masonry sealer to the top coat once its all dried.

I take it lime render is no good then for keeping water out then?

 

[Rossi46]

The paint on the external render will keep the water out.

 

[fobos8]

they don't want paint on the render. They want a rustic finish like this

 

[Rossi46]

they don't want paint on the render. They want a rustic finish like this

Ahh sorry I missed that.

 

[Rossi46]

they don't want paint on the render. They want a rustic finish like this

That is course isn’t it!

 

[Rossi46]

I think your idea of a masonry sealer would work. The customer gets what they want and without the problem of any ingress. The likes of Stormdry dries without any shine so you’d never know it was on.

 

[raggles]

thanks raggles - that sounds like a good idea. If I slurry the blockwork with sbr and put sbr in scratch coat too will that help keep the water out or would it be better off just applying a clear masonry sealer to the top coat once its all dried.

I take it lime render is no good then for keeping water out then?

thanks raggles - that sounds like a good idea. If I slurry the blockwork with sbr and put sbr in scratch coat too will that help keep the water out or would it be better off just applying a clear masonry sealer to the top coat once its all dried.

I take it lime render is no good then for keeping water out then?

Yes you could use it but why when it is not a listed building or the like. You can achieve a similar finish with cement without all the after care bollox of lime and using lime externally at this time of year would be a right knacker ache. Make life easy for yourself where ever possible and this to me sounds like one of those occasions.

 

[flynnyman]

Either way it's going to be a solid wall so if you use lime on the outside what's happening on the inside will have consequences.

 

[fobos8]

Raggles - what is the after care bollox of lime render?

Would be very useful to know what the downsides are. All the stuff I've found out from Google is positive.

 

[raggles]

Raggles - what is the after care bollox of lime render?

Would be very useful to know what the downsides are. All the stuff I've found out from Google is positive.

OK if you use sand and cement it is pretty much use and forget if you know what your doing. A lime based render however depending on the time of year will need to be looked after is in summer misting with water to prevent it drying too quickly cracking and failing then waiting until it is cured properly before you can get the next coat on. In Autumn/ winter the reverse applies and you you need to protect from the elements frost etc and it could take weeks for the scratch coat to cure and same for the top coat and all the while someone needs to be checking it.
Lime renders are great products and for older properties are in many many cases the best way forward however, when your building with concrete blocks and single skin concrete blocks I would argue the benefits of a so called breathable lime render are wasted and the same aesthetic could be achieved with a cement render which would cost less from a materials and labour perspective.

 

[fobos8]

Brilliant - many thanks for the explanation. Might go for a Parex mineral render and scratch it up.

Cheers, Andrew

 

[fobos8]

once it is on though are there any long term after care maintenance issues?

 

[stiltwalker]

I just turned down a external lime job on a 5 bed listed house due to starting in December! Some companies never listen

 

[Dropsalot]

I just turned down a external lime job on a 5 bed listed house due to starting in December! Some companies never listen

Hahaha.........some t**t full of piss and importance invoking the Christmas deadline I expect......The trouble with the world we live in....no-one has any patience.

 

[stiltwalker]

Hahaha.........some t**t full of piss and importance invoking the Christmas deadline I expect......The trouble with the world we live in....no-one has any patience.

Yes you are totally correct plus the funny thing was they wanted you to work to a schedule of about 3 weeks plus sign a contract and retention and all the other b*ll***s that goes with it

 

[Dropsalot]

Yes you are totally correct plus the funny thing was they wanted you to work to a schedule of about 3 weeks plus sign a contract and retention and all the other b*ll***s that goes with it

Pffft!!!