victorian terrace -Fireplace -back casting?

[AnimalJack]

Hi -I know this is way off the Moggy track -but ive found that many fellow moggy owners tend to have similar habits....so here goes...
Im renovating an old terrace house and ive re opened all the fireplaces.......Ive used firebricks in the three upstairs (like the type you can buy in lots of places ..2 angled sides and one rectangular back -yellowish) They are fixed in with fire cement .............but above them ,and up into the chimney flu is all pointed stonework as all the casting had fallen out years ago ......so I need to plaster/re -render all backs and sides with a cement mix. The original stuff that was piled up behind the blocks when I reopened them , was quite light in weight -limey maybe. So the bottom line is ...does anyone know what that mix would be . I tried a natural fireclay that can be found in these parts and is great for stove jointing and the likes - but after Id done a lovely job of casting all the backs - it mosaic -cracked like an African river bed in summer . So Im hoping someone may know what mix would they have used -as to my mind I think, they would only have had say clay, lime and ash available ? (ive searched on line -but I could only find mixes for building kilns etc and a bit ott for what im trying to do)
Any help would be great Thanks, AJ.

[philthehill]

Living in an old Cob built house I am always using old fashioned lime mortar for the brickwork and plastering walls - lime mortar dries (it does not actually dry but goes solid through chemical process when exposed to the air) and to control the drying rate you have to spray the mortar with water whilst it is drying.
Have a look at the attached link and if you cannot find what you want have a word with them they are always very helpful.
I get all my lime requirements from them in ready mixed tubs which have a top covering of lime water which is drained off and the lime mortar mixed and then used - lime mortar should be used when it is the consistency of stiff treacle - the surplus is put back in the tub and the lime water returned to covering the solids.
Lime mortar does not go off and improves with age and a tub can be used over many years.

http://www.thelimecentre.co.uk/

If you want to use a cement mix - a mix of around 4 or 5 parts of sharp sand to 1 of cement should be suitable but using lime mortar gives more satisfaction and it enables the bricks etc to be removed at a later date if required.
Try a small amount of cement mix in a block and see what it dries like -you can always add more sharp sand to weaken the mixture until you are satisfied with its strength.

If you need any more help please come back to me.
Phil

[AnimalJack]

Thanks for that ! I will get in touch with the centre and let you know how I get on . A.

[SteveClem]

I agree with Phil. Lime mortar is better for old houses. We tried both when we renovated an early 19th century range of farm buildings and the traditional stuff looked better and moved with the buildings. The sand and cement cracked with seasonal movement. The buildings didn't have proper foundations, they were built on massive flagstones, so there was a bit of wobble at times.

[Propshaft]

If you intend to use the fire as a traditional fire ie burning wood or coal I would advice putting in a flue liner either stainless steel copex or having a cement based one by a specialist

[taupe]

Hi

if your chimney needs only a little reparging then this is the stuff or you can have a contractor do the whole chimney...25 year warranty..

http://www.landyvent.co.uk/eldfast

or a pic http://www.mccarten-builders-cornwall.com/chimneys.htm

Taupe

[irmscher]

Jack don't forget to have the chimney swept

[olderisbetter]

Totally agree with lime mortars and plasters, i have seen old houses repointed with cement products and it fetched some of the brick faces of as it gives no movement, My own fires in the house have been used after we refitted them and have been no problem, one thing we did do is fill the voids between the bricks and the cast with vermiculite to reflect the heat forward, but each install will be different.

[AnimalJack]

Thanks for all the help so far ...........Im going to try again with a lime mortar mix as the more I think about it they would only have had Lime , Ash and soil -and possibly sand , to work with and the bits of original back castings that I found were very porus -lightweight and looked like a mix of ash and lime .
The part that im doing is the back and sides -directly above the fire bricks, so it will get quite hot and then up into the flu- which are now lined ...........so its rendering /casting the inner back and sides of the fireplace.