Lime mortar for pointing & rendering a rubble stone wall

[Scullerdude]

I need to repoint the stonework on my house and also apply a thin render. Two exterior walls are rubble walls with a mixture of red sandstone & a hard black impermeable stone (Schist?).

I am intending to use a Lime mortar for re-pointing and for applying a thin render.

As I have never done this before, has anybody have any tips or advice on sourcing & working with Lime?

Many thanks
Martin

Rear rubble stone wall

• Scullerdude
• 17 Jul 2010
• 1

 

[troweladdict]

looks like it needs a rerender m8te best way is. To remove all the old stuff.
Then brush off the brick work wetting the wall with water to help the suction.
ill set the beads now i use board addy with pva sets in no time and is water tite so no cracking and you can leave over night.
Then stat with a 4/1 mix of plastering sand and cement wth a bash of water proofer working the render till flatish rule off as you go filling dips (dont over work it)
Use a scracher over the render at the end of the day.
next day wet the way agen this will help with suction and help too key the render together.
starting with a mix of 5/1/1 five sand /1cement/1 hydreted lime
(no water proofer) then get it on thw wall working it over the scrach coat.
Then ruil off filling dips you may need to do this more then once
let it pull in the render will start to go keping a bucket of the render will help for filling dips.
use a jumbo car spoge with clean water rubing softy in a circuar motion away from you (rubing up)
then as you go if you see littel dips then use a poly float too rub in some render over it.

 

[Micilin]

looks like it needs a rerender m8te best way is. To remove all the old stuff.
Then brush off the brick work wetting the wall with water to help the suction.
ill set the beads now i use board addy with pva sets in no time and is water tite so no cracking and you can leave over night.
Then stat with a 4/1 mix of plastering sand and cement wth a bash of water proofer working the render till flatish rule off as you go filling dips (dont over work it)
Use a scracher over the render at the end of the day.
next day wet the way agen this will help with suction and help too key the render together.
starting with a mix of 5/1/1 five sand /1cement/1 hydreted lime
(no water proofer) then get it on thw wall working it over the scrach coat.
Then ruil off filling dips you may need to do this more then once
let it pull in the render will start to go keping a bucket of the render will help for filling dips.
use a jumbo car spoge with clean water rubing softy in a circuar motion away from you (rubing up)
then as you go if you see littel dips then use a poly float too rub in some render over it.

Just one thing here, addict -why use board adhesive, designed for internal use only, for outside work? That's got to last in wet conditions for as long as the render

Use the material you need for outside work to fix the beads . You should stick the beads with sand and cement when rendering outside. I can't think of any good reason to do otherwise?

 

[woodgnome]

What is the pointing + render in photo made of ? .What type of finish is on the other to walls ? . How exposed to weather are the walls ? . More pics ?. Working with traditional lime rather than a cement based mortar requires more time and attention to detail due to the fact that it cures using an air drying process , not a chemical one . More preparation and careful application is needed as the finished material is inherently weaker , and is not relying on p.v.a + chemicals to stick it to the stones like cement . To avoid crackingfrom sun / wind the work must be protected with plastic sheeting . You dont want to be working in temperatures below 10 degrees as the carbonation (drying) process will not work leading to mechanical failure .The traditional time for outside limwork is spring / early autumn , avoiding both hot sun and frost . The advantages of this slow setting time is that you dont have to clean tools / scaffolding if taking along lunch break . Dont use anything with cement in it as it will ruin your old buildings' breathability .

 

[stevethespreader]

if your going to render the walls its a waste of time repointing, as a matter of fact my advice would be to take the rest of the render off and rake the bed joints back for a better key then apply render

 

[roughcaster]

looks like it needs a rerender m8te best way is. To remove all the old stuff.
Then brush off the brick work wetting the wall with water to help the suction.
ill set the beads now i use board addy with pva sets in no time and is water tite so no cracking and you can leave over night.
Then stat with a 4/1 mix of plastering sand and cement wth a bash of water proofer working the render till flatish rule off as you go filling dips (dont over work it)
Use a scracher over the render at the end of the day.
next day wet the way agen this will help with suction and help too key the render together.
starting with a mix of 5/1/1 five sand /1cement/1 hydreted lime
(no water proofer) then get it on thw wall working it over the scrach coat.
Then ruil off filling dips you may need to do this more then once
let it pull in the render will start to go keping a bucket of the render will help for filling dips.
use a jumbo car spoge with clean water rubing softy in a circuar motion away from you (rubing up)
then as you go if you see littel dips then use a poly float too rub in some render over it.

Just one thing here, addict -why use board adhesive, designed for internal use only, for outside work? That's got to last in wet conditions for as long as the render

Agree with you completely Micilin,,
and would also add that "NO" beading, should EVER be fixed to a solid wall/corner,, using dabs of plaster,,, (especially outside) ,,, if the wall is going to be cement rendered.

Not a problem if the wall/s (internally), are going to be plastered, (float and set).

You can put a coat/s of plaster over dabs of render, that are holding a bead in place,, but you should never put a coat/s of cement render over dabs of plaster that are holding beads in place.

We had a similar chat about this just a few weeks ago, if i remember correctly.

 

[woodgnome]

Hi Sullydude-I presumed that you were intending to use natural lime [non-hydraulic or hydraulic] to repair your walls?I dont think just adding a bit of hydrated[powdered] lime to a cement and p.v.a mix is quite what you meant.If Im wrong then you shouldent have any worries about sourcing a few bags of Hydrated lime -if Im right,then you probably dont want to follow the methods described in the last few posts.

 

[Scullerdude]

Hi All,
Thank you all for your posts. I have been led to believe that the exterior wall in question is a Lime mortar & render and as such I should replace it like for like to avoid damaging the stone with a mortar (containing cement) that is too hard & impermeable to water. I should have explained that this house is perhaps 150 years old.
Thanks again.

 

[Mad_Doctor_X]

There's a place down in Devon that will sell you premixed lime mortar and plaster (I'm not sure what the rules are on posting links to commercial companies on this website).

They also sell a DVD that I found quite useful.

 

[external]

forget lime,its rubbish,bollt some insulation on and tight coat and fix all your probs with one shot!!!