Lime bell casing

[slumberland]

Hi Guys
I have got a flemish bond wall and there is some bad weathering to the first few courses where the bricks protrude out further..My attached neighbour has a cement render bell casing. In dont want to cement render mine. When we fixed up the property i injected a chemical damp course and waterproofed the inside with cement render.
In hindsight i might have limed the wall but it was fairly weak in places and a cement render keyed it all together.
I figure if I use a lime bell casing and re-point the wall (taking out the cement pointing) the wall will at least breath outwards and any damp trapped will get out.
I will repoint in nhl2 + 3 parts sharp sand any ideas how to mix and do I need a mixer or can i do it by hand. The same mix fo the bell casing in a couple of layers.
Any thoughts please.

Where can i get nhl2 in Ely Cambridgeshire and does any one know a architect this way my cottage is needing a sympathetic extension?

Thanks Jason

 

[chuckey]

On the back of St Astier lime they say use a good cement mixer(?) and mix for at least 20 minutes. I have found that its a pain, adding water over say, 5 minutes results in what looks like a mix that is too dry. When you leave it mixing after 20 mins or so , the mix is too wet. So providing your sand is of a consistent dampness, gauging the water is a requirement. Try it out and see how your lime reacts.
Frank

 

[Mark]

I would start by just repointing in lime. like many others I use bog standard bagged lime in a ratio 3 sand : 1 lime (by volume).

You might choose to either decant the lime into a tub and cover in water first or to make up dry then mix and add water and leave for a couple of days.

Although making up with dry lime and using immediatly works, It feels nicer to work with after a little time maturing.

 

[biffvernon]

Singleton Birch is the English producer of nhl2.

 

[Lime]

On the back of St Astier lime they say use a good cement mixer(?) and mix for at least 20 minutes. I have found that its a pain, adding water over say, 5 minutes results in what looks like a mix that is too dry. When you leave it mixing after 20 mins or so , the mix is too wet. So providing your sand is of a consistent dampness, gauging the water is a requirement. Try it out and see how your lime reacts.
Frank

A very tiny squirt of washing up liquid in the water used for the mix speeds the whole process up.

 

[Tom]

Singleton Birch is the English producer of nhl2.

Castle also produce NHL2.

Jaqy

 

[Tom]

like many others I use bog standard bagged lime in a ratio 3 sand : 1 lime (by volume).

Ty-Mawr Lime have this to say about Hydrated (bagged) Lime;

" Foresight Project - "Scientists at Bristol University have calculated that using blue lias hydraulic lime instead of cement for building has an energy saving of around 40%"
This is not the hydrated lime sold by most builders' merchants which is a non-hydraulic lime powder, produced by slaking Quicklime with a shortfall of water. It is often considered to be an inferior product to the limes described above for a number of reasons but primarily because it starts to carbonate from the moment it is made and can actually fully carbonate in the bag before use. Widespread use of 'bag' lime has given 'lime' a poor name because of the instances where it simply has none of its original properties left by the time the end-user works with it - hence it fails, dusts etc."

Quoted from http://www.lime.org.uk/products/p2794.asp

Jaqy

 

[slumberland]

Hi Guys
Have you any thoughts on the bell casing?
Can I paint it and how deep do i need take it. It really is just to smarten the weathered bricks and to cause the water to run of the the top where the bricks jut out.
Thanks for your replies.

 

[Nemesis]

Don't worry too much about the stuff re bagged lime carbonating in the bag etc. Buy it fresh, keep it dry. Bags these days tend to be plastic lined.

However - hydraulic lime and hydrated lime both come in bags.

Hydrated lime mixed with water will make non-hydraulic lime putty.

Hydraulic is certainly better than cement for modern building purposes, for reasons of saving the planet etc, but for historic building work should be used with caution.

For most pointing etc purposes either bought non-hydraulic putty or putty made with hydrate is first choice.

 

[charlie-ia]

sorry- what is a bell casing?

 

[slumberland]

Sorry Im not sure if thats the right term.
The rendered part of a wall. Usually to about 2 foot up, often painted black my neighbours is cement grey I would like mine to be lime as his is cracked.
Jason

 

[inwood]

I think what you're referrring to is a 'Bell cast'. You can see a picture of it here:
http://www.expamet.co.uk/bp/products/570.html

It's used to provide a nice finish to the bottom of rendered walls, since the render can't breach the DPC/DPM, although I think it can sometimes look a bit twee/contrived.

Of course if you're using lime and you don't have a DPC/DPM then the render can go to the base of the wall since the lime allows any moisture to evaporate from the wall.

If you have a DPC/DPM then I would recommend finishing the render above this. You don't have to use a bell cast for this though, the render can simply be cut off above the DPC/DPM in a straight line. B&Q or any builders merchants sell bell casts - you'll find them in the plaster/plasterboard sections of the stores.

 

[Raylea]

We have it on our new extension and it looks just like its said the bottom of a bell and it starts about three bricks up from the ground.

Raylea