Lime Render

[Mark A]

Hi chaps,

We're in the process of renovating our house and we've reached the stage where we think about the walls.

Anyone had any experience of lime render, both internally and externally?

Are the properties of lime render still favourable over modern cement renders and/or plaster?

Cheers,
Mark

 

[RogerS]

It depends on what you are rendering over. If it's a traditional brick construction with Portland cement then I don't see any point. But if it is an older property and the mortar between the bricks or stones is lime then it makes a lot of sense. Be wary of what you then paint or decorate the lime mortar with. There are special paints to go on top of lime to let it do what it's good at - ie 'breathing'.

The nice thing about lime mortar is that it never goes off in the bucket! As I recall, however, the application of lime render is different to cement based render. Are you doing it yourself?

 

[lurker]

Both my home and the "refurb" house I'm doing have lime mortar, so I decided to get some to repoint

A bluddy great bucket cost me about £20 with delivery (delivery was the bulk of the cost)
Its quite easy (easier than using portland) and it looks much better.
And as Roger says its does not "go off in the bucket" so I'm hoping I have enough to last a lifetime
Pointing is one of those jobs were I can't do more than an hour at a time (or I start to get slap dash!) so cutting out the mixing and shade matching every time is a real boon.
Will get back on it when the weather warms up; I have tens of square metres to do :x

I realise this is not what the OP asked but in my view lime mortar & render are excellent for the purpose because of the breathability.

 

[Mark A]

It depends on what you are rendering over. If it's a traditional brick construction with Portland cement then I don't see any point. But if it is an older property and the mortar between the bricks or stones is lime then it makes a lot of sense. Be wary of what you then paint or decorate the lime mortar with. There are special paints to go on top of lime to let it do what it's good at - ie 'breathing'.

The nice thing about lime mortar is that it never goes off in the bucket! As I recall, however, the application of lime render is different to cement based render. Are you doing it yourself?

Hi Roger,

The house is a bit of an odd one: the original part dates back to mid-late 1800s and was a typical 'two up two down' double-fronted cottage of rubble wall construction, but since then it's been extended two or three times over the years.

The side and back of the house are a mixture of brick and block cavity and stone; though it's the old part which suffers from the most damp. This is undoubtedly exacerbated by the fact that the external render is completely blown and the ground on one side is higher than the internal floor level.

Over the next couple of months we aim to hack off all the render and give it time to dry out before re-rendering. The garden will also be pushed back enough to enable us to install proper drainage along the side of the house. As you say, it's a bit pointless using lime render over over the more recent brick and block walls so I'm wondering if it's possible to use cement render on them and lime render for the stone.

If we go down that route for the external walls, what approach should we take with the inside?

If the exterior stone walls are lime rendered would we have to do the same to the interior or would one side be enough to rectify the problem, ie lime outside and cement inside?

Cheers,
Mark

I'm typing on my phone while wearing gloves so I hope it makes sense!

 

[blackrodd]

I've done some of this, Plastering and dry lining etc, new and old.
If you live in a rainy part of the country, I wouldn't like to hack off what little plaster protection you have,and leave it, hoping to dry out.
I would repair, dubb out and scratch coat as swiftly as you can, hard rain can strip and penetrate a surprising amountof cob or older lime mortars.
lime mortar in stone or brick will burn off subsequent cement renders, so keep a shovel of lime in every "gauge", or mixer full when you render outside on older stone or brick.
Pit or quarried sand, such as good old Wickes sell is best and strongest, I recommend it! It makes a smoother plastering material, not needing additives, plasticisers, etc
Sea sand is often not washed, clean enough, and the impurities it can have do lead to problems burning through at a later stage.
Sounds like you are laying a french drain, excellent idea! pipe it away from the house, to a soakaway, a good opportunity to link any existing gutter/surface water and get it away.
When the dubbing out and repair work is done and the scratch coat is on, I fix a 2x1 batten 12" from the path level,
and use this to form a "bell cast" and throw any water off, from the top finished coat.
Carefully removing the batten, The remaining plinth, is plastered and sponged up to a finish, and then THIS is the drying area, at the wall base, where it needs to breathe so I paint this 12" plinth with lime wash.
The rest of the wall I paint with exterior masonry paint.
On the interior, I hack and strip the existing plaster, rads and electrics. repair any wall defects, particularly at the lower wall areas, where it is dampest, and ready for Synthaproof, as Wickes sell.
Egatube electric cables to switch positions, and apply synthaproofx 2, or 3 coats,1500mm up the wall and dash with sand on the final synthaproof coat.
I plaster with Carlite Bonding coat, it sticks like the proverbial, it is lightweight and full of vermiculite as a retardant but it is good at insulation, on you're new wall finish, You can lay it on in excess of 2" thick if needs be.
This I trowel or sponge up to a finish. Its a bit soft for some people, A typical carlite plaster but the advantages outweigh the soft aspect in my opinion.
You can also render and set or even dry line with insulating boards, if you choose.
Electric sockets and switches, are surface, so as not to compromise the synthaproof damp treatment fixing screws are in plastic plugs.
HTH Regards Rodders

http://www.limestuff.co.uk/pages/user-g ... -lime.html

 

[AndyT]

I'm convinced that on an older property, flexible, breathable lime render is the way to go.
We had some excellent work done by a local specialist who recommended Ty Mawr coatings to go on as a decorative finish. Far more durable than limewash. Lots more here

https://www.lime.org.uk/ty-mawr-paint-ranges/

 

[RogerS]

Yup, Mark. I'd stick to cement on the 'modern' stuff and lime on the older parts.

Personally I would put in a proper plastic type drain channel - the one with the grill on top. French drains are useless and clog up. People talk about laying some weed matting in the channel and then laying more stone on top of that. All that achieves is that the layer of impermeable clay/whatever now sits on top of that matting. The water never gets a chance to go down into the drain easily.

As far as internal walls are concerned, I'm not really an expert. I have used Synthaprufe and it's great stuff.

 

[Paul200]

Hi Mark. We've faced similar problems in our old property in Somerset and also now here in Galloway. Old walls need to breath inside and out - it's the only way for them to lose moisture that's taken up from the ground when there's no dpc in place. It's important to get the finishings right, even down to the type of paint.

I'm no expert but I've done a lot of research. Here's a couple of links to help you out. The Heritage House site can be a bit, shall we say, evangelistic, but stick with it - there's a lot of good, practical advice in there. The second site, Limebase, is a company that has done conservation work on various important buildings around the country. These guys really know their stuff and were a great help to me when I needed to repoint our house. No job is too small!

http://www.heritage-house.org/the-fraud ... -damp.html

http://www.limebase.co.uk/

Good luck!

 

[Mark A]

Hi chaps,

Thanks for the advice so far, it's much appreciated.

Paul - I'm working on the house now so will take a look at the links you provided when I get home later tonight.

Cheers,
Mark