Rendering behind wood burner

[mike]

What's the best mix to render brickwork in an old fireplace prior to installing a wood burner? I've seen the following suggested:

0:1:3 cement: hydrated lime: plastering sand 1:1:3 cement: hydrated lime: plastering sand 0:1:3 cement: NHL2.5 hydraulic lime: plastering sand and similar recipes but with 5 parts sand.

Anyone have any thoughts on which, if any, is best?

Two coats / top coat weaker?

Prime with cement slurry or PVA?

Can the render be just thick enough to even out the wonky brickwork or does it need a certain thickness for stability?

How long before it can be painted? Can it be painted or does it need whitewash? Is it possible to make a small quantity of whitewash from the lime?

There seems to be quite a variety of opinions online so would be nice to hear from someone who's been there, done that, got the T-shirt.

[polygonum]

I thought the traditional approaches involved fresh cow dung, lime, sand and goodness knows what else. If it really is an old fireplace, it is likely to have some tars held within the material which could weep, especially when heated.

[Brian Gaff]

Did you see call the council the other day. something I never knew, in smoke free zones on has to fit special Defra approved burners that do not emit the half burnt smoke apparently. Several people have been banned from brning logs on ones not so approved after complaints about eh smoke. I would have thought it would be enviornmental agency, not Defra myself. So beware your idilic wood burner could upset the neighbours give you a nasty fine and leave you with a shed full of logs you cannot burn. Brian

[charles]

As far as I know the Environment Agency is a part of DEFRA. I suspect an "Agency" is unable to make rules - it would be up to the parent department.

[Tim Watts]

Having done this, I can say what works:

Lime, cement, sand. Cannot remember the ratio, but

1:1:3 cement: hydrated lime: sand looks about right.

In my case, I wanted to whitewash it for a light heatproof finish.

I used Snowcrete and silver sand for a white ish render mix.

I mixed a slurry of snowcrete and painted that on the brickwork

*immediately* prior to rendering for a good bond. It has not fallen off in 4 years and it gets *very* hot.