Mostly just checking - I tend to get quite nervous when embarking on
the next job.

I have quite a bit of plastering to do onto bear rubble/mud built
walls. They did have a layer of mud and straw covered with lime
plaster, but the mud and straw daub has given up adhering to the
walls. I'm left with very rough walls, which present about 1/3rd mud
facing, which isn't particularly strong. Unless someone stops me, I'm
going to apply a 1:2.5 mix of Castle hydraulic lime and "plastering
sand".

I am toying with the idea of spraying the walls with some pva fist?

If it all goes horribly wrong, what's the best type of plaster to use?

T

wrote in message
...
Mostly just checking - I tend to get quite nervous when embarking on
the next job.

I have quite a bit of plastering to do onto bear rubble/mud built
walls. They did have a layer of mud and straw covered with lime
plaster, but the mud and straw daub has given up adhering to the
walls. I'm left with very rough walls, which present about 1/3rd mud
facing, which isn't particularly strong. Unless someone stops me,
I'm
going to apply a 1:2.5 mix of Castle hydraulic lime and "plastering
sand".

I am toying with the idea of spraying the walls with some pva fist?

If it all goes horribly wrong, what's the best type of plaster to
use?

T

If it's mud wall then I'd expect you to need a breathable plaster such
as lime

AWEM

wrote:
Mostly just checking - I tend to get quite nervous when embarking on
the next job.

I have quite a bit of plastering to do onto bear rubble/mud built
walls. They did have a layer of mud and straw covered with lime
plaster, but the mud and straw daub has given up adhering to the
walls. I'm left with very rough walls, which present about 1/3rd mud
facing, which isn't particularly strong. Unless someone stops me, I'm
going to apply a 1:2.5 mix of Castle hydraulic lime and "plastering
sand".

I am toying with the idea of spraying the walls with some pva fist?

If it all goes horribly wrong, what's the best type of plaster to use?


rubble and mud walls? - the house must be 500 years old? - isn't there a
preservation order on it?


If there is only a room or two to do, and assuming you want to preserve the
walls intact for posterity, this would be my plan of attack:

vapour barrier entire wall(s)
build studding tight up to wall(s)
insulate with fibreglass
plasterboard and skim

this makes for a warmer, straighter and condensation free wall, and if needs
be, in the future you can take down the stud walls and there are the
mud/rubble walls intact.

I don't think sand & lime will stick to mud


--
Phil L
RSRL Tipster Of The Year 2008

On Thu, 18 Dec 2008 15:12:00 GMT, "Phil L"
wrote:

wrote:
Mostly just checking - I tend to get quite nervous when embarking on
the next job.

I have quite a bit of plastering to do onto bear rubble/mud built
walls. They did have a layer of mud and straw covered with lime
plaster, but the mud and straw daub has given up adhering to the
walls. I'm left with very rough walls, which present about 1/3rd mud
facing, which isn't particularly strong. Unless someone stops me, I'm
going to apply a 1:2.5 mix of Castle hydraulic lime and "plastering
sand".

No I dont think thats a good idea

walls intact for posterity, this would be my plan of attack:

vapour barrier entire wall(s)
build studding tight up to wall(s)
insulate with fibreglass
plasterboard and skim

this makes for a warmer, straighter

I find it interesting that straighter is considered to be an
advantage. You are not the only person to think so - straight walls
have been desired since the neoclassical revival of c1780 but before
then people didnt think straightness important. In an old house which
originally had no pretensions to classicism it is more characterful
and of its time if the walls wander around a bit and you aim for
continuous but not straight walls (easier to DIY too)

be, in the future you can take down the stud walls and there are the
mud/rubble walls intact.

Yes that would work I expect, I have never tried but it counts as a
good conservation method if it leaves the walls intact

I don't think sand & lime will stick to mud

Yes it will. My house is just that. Well no its clay not mud but I
expect thats what the OP has too. So long as the clay is dry it will
be fine

Dont make the common mistake that strong = good

The rule to follow is that each layer should be weaker than the one
underneath. Your daub wall is not strong so whatever goes on to it
should be as weak as possible so if you decide to use lime then use
the weakest lime mortar you can get which is lime putty mortar not
hydraulic lime mortar

Any daub which is actually falling off can be removed first but dont
go poking around to see if any more will come away because it all
will. If you want to be economical of lime and time* then mix up some
more daub and use it to level up the walls not forgetting to scratch
the surface to give the lime mortar a good key

* Daub just dries so you can blast heat at it if you want to dry it
PDQ. Lime has to be built up in 10mm layers and each layer has to set
before you add the next. To be on the safe side leave 3 weeks between
layers

Dont forget to damp down the wall before adding the next layer

Lime needs CO2 and water to set so keep the room cool/warm (not hot -
water will evaporate, not cold - it will take forever to set) and add
a fan heater to blow the air around

Anna
--
Anna Kettle
Lime plaster repair and conservation
Freehand modelling in lime: overmantels, pargeting etc
Tel: (+44) 01359 230642
Mob: (+44) 07976 649862
Please look at my website for examples of my work at:
www.kettlenet.co.uk

Anna Kettle wrote:
On Thu, 18 Dec 2008 15:12:00 GMT, "Phil L"
wrote:

wrote:
Mostly just checking - I tend to get quite nervous when embarking on
the next job.

I have quite a bit of plastering to do onto bear rubble/mud built
walls. They did have a layer of mud and straw covered with lime
plaster, but the mud and straw daub has given up adhering to the
walls. I'm left with very rough walls, which present about 1/3rd mud
facing, which isn't particularly strong. Unless someone stops me, I'm
going to apply a 1:2.5 mix of Castle hydraulic lime and "plastering
sand".

No I dont think thats a good idea

walls intact for posterity, this would be my plan of attack:

vapour barrier entire wall(s)
build studding tight up to wall(s)
insulate with fibreglass
plasterboard and skim

this makes for a warmer, straighter

I find it interesting that straighter is considered to be an
advantage. You are not the only person to think so - straight walls
have been desired since the neoclassical revival of c1780 but before
then people didnt think straightness important. In an old house which
originally had no pretensions to classicism it is more characterful
and of its time if the walls wander around a bit and you aim for
continuous but not straight walls (easier to DIY too)

be, in the future you can take down the stud walls and there are the
mud/rubble walls intact.

Yes that would work I expect, I have never tried but it counts as a
good conservation method if it leaves the walls intact

I don't think sand & lime will stick to mud

Yes it will. My house is just that. Well no its clay not mud but I
expect thats what the OP has too. So long as the clay is dry it will
be fine

Dont make the common mistake that strong = good

The rule to follow is that each layer should be weaker than the one
underneath. Your daub wall is not strong so whatever goes on to it
should be as weak as possible so if you decide to use lime then use
the weakest lime mortar you can get which is lime putty mortar not
hydraulic lime mortar

Any daub which is actually falling off can be removed first but dont
go poking around to see if any more will come away because it all
will. If you want to be economical of lime and time* then mix up some
more daub and use it to level up the walls not forgetting to scratch
the surface to give the lime mortar a good key

* Daub just dries so you can blast heat at it if you want to dry it
PDQ. Lime has to be built up in 10mm layers and each layer has to set
before you add the next. To be on the safe side leave 3 weeks between
layers

Dont forget to damp down the wall before adding the next layer

Lime needs CO2 and water to set so keep the room cool/warm (not hot -
water will evaporate, not cold - it will take forever to set) and add
a fan heater to blow the air around

Anna

It sounds like the OP could really do with doing some basic reading on
historic properties before doing anything. Maybe ask on the
http://periodpropertyshop.co.uk/ forum.


NT

On 18 Dec, 17:03, (Anna Kettle) wrote:
On Thu, 18 Dec 2008 15:12:00 GMT, "Phil L"
wrote:

wrote:
Unless someone stops me, I'm
going to apply a 1:2.5 mix of Castle hydraulic lime and "plastering
sand".

No I dont think thats a good idea


Any particular reason?


I don't think sand & lime will stick to mud

Yes it will. My house is just that. Well no its clay not mud but I
expect thats what the OP has too. So long as the clay is dry it will
be fine


It has stuck, and the walls have no clay in them. The "mortar" is in
fact the local subsoil.

Dont make the common mistake that strong = good


What do you mean by "strong"?

The rule to follow is that each layer should be weaker than the one
underneath. Your daub wall is not strong so whatever goes on to it
should be as weak as possible so if you decide to use lime then use
the weakest lime mortar you can get which is lime putty mortar not
hydraulic lime mortar


Unfortunately the original builders didn't take your advice and put a
weak, soft, topsoil+straw mixture on before the relatively "strong"
lime plaster.

Any daub which is actually falling off can be removed first but dont
go poking around to see if any more will come away because it all
will. If you want to be economical of lime and time* then mix up some
more daub and use it to level up the walls not forgetting to scratch
the surface to give the lime mortar a good key


Where does one get daub from, and how do you mix it into a consistency
that is both workable and will produce a durable layer? Are you
suggesting I dig up my garden?

* Daub just dries so you can blast heat at it if you want to dry it
PDQ. Lime has to be built up in 10mm layers and each layer has to set
before you add the next. To be on the safe side leave 3 weeks between
layers


Alternatively a cement render will do a perfect job in a fraction of
the time for a fraction of the price. There are sections of wall that
have been repaired that way, and they are in perfect condition.

Your clients are obviously the sort who have an excess of money and
patience. Unfortunately, I'm just an average person with the usual
time and financial constraints.

Dont forget to damp down the wall before adding the next layer


In all the excitement I did forget to dampen the first area of wall I
rendered. It did result in a few cracks, but they just close up with a
trowel. Dampening the other areas didn't make any difference.

Please look at my website for examples of my work at:www.kettlenet.co.uk

Very impressive! Your amazing work would look totally out of place in
my house though...

T

Phil L wrote:

vapour barrier entire wall(s)
build studding tight up to wall(s)
insulate with fibreglass

Not a good idea: in the winter the VB is on the cold side of the
insulation and you'll get condensation on its inside surface rotting the
new studwork. In summer if the outside wall gets a soaking in a shower
and then the sun comes out you could get condensation of the outside
surface of the VB, rotting the old wall.

--
Andy