pointing , raking out, style and sand grade?

[robgil]

ok , first off , raking out. where do you stop? in places i could rake out right through to the other side so do i go half way then do the pointing?

style of pointing , probably built around 1670 so what style of pointing do i use? inside and out the same?

and finally the mortar , what grade / type of sand if any is in this? it looks very lime rich and crumbles to a powder however there is some large stones and pebbles in it. anybody know the make up of a mortar like this?

 

[chuckey]

Depth of raking is about twice the height of the joint - 20mm ?. Your sand would have been sourced locally, try dredging the local river, or failing that, use a sharp sand with the same colour. A proper lime supplier/restoration supplier should have a selection.
Frank

 

[Gervase]

What chuckey said, essentially. When you're raking out, save the stuff you remove and use that as part of the aggregate you're using. If you're ordering pre-mix mortar, send your supplier a sample so they can match it.
As a rule of thumb, with a coarse sand like that you'll be looking at a 2.5:1 sand:lime mix, but a 3:1 mix should be fine.

 

[robgil]

thanks guys , the mortar is really chalky white so do you think this might mean its got less sand in it or even perhaps some chalk ? it also crumbles to a fine powder.

 

[Flyfisher]

I'm certainly no expert, but I've read that some mortars were very lime-rich; sometimes 1:1.

If you're particularly concerned to achieve a good match, you could have a sample analysed. I don't know where or how much it would cost, but I'm sure someone here would know.

 

[andrew gayton]

the chalky bits are undoubtedly unslaked quicklime. I am of the opinion that the 1:3 ratio refers to the use of quicklime and sand. once the mix was watered, mixed and the lime slaked, the quicklime could almost double in volume. i would suggest a 1:2 mix with a sharp sand, 3mm down to 150 microns (a typical 'sharp' sand)

although, one has to ask, was it originally pointed or plastered??

 

[robgil]

it was plastered at some point,when we uncovered it all from under the cement wall there was some plaster that had fallen away from the bricks but only a few small patches and there are traces of plaster on most of the brickwork.
strangely there was no traces of plaster at all on the bricks at the back. i would like to put the plaster back at some point but ms robgil is a lover of exposed brick so she may take some convincing.
the pointing that remains or at least traces of it look to be flush but kind of untidy , not all square and flat if that5 makes sense, if the builders knew they were going to plaster the chimney would they have not bothered to do neat pointing?

also , would they have used putty for the mix?

 

[Jill]

If you're particularly concerned to achieve a good match, you could have a sample analysed. I don't know where or how much it would cost, but I'm sure someone here would know.

Try Singleton Birch based at Melton Ross, in North Lincolnshire. They have a lab to do the testing of there own lime products. I don't know if they do any external testing though. Do an internet search and you'll find the contact details.

 

[Flyfisher]

the pointing that remains or at least traces of it look to be flush but kind of untidy , not all square and flat if that5 makes sense, if the builders knew they were going to plaster the chimney would they have not bothered to do neat pointing?

I doubt they'd have bothered with neat pointing if the brickwork was going to be plastered at the time. Indeed, 'untidy' pointing would be an advantage I'd have thought when it came to applying the plaster.

 

[andrew gayton]

bear in mind that the 'pointing' you see now, is relatively friable, has been exposed for some time and no doubt 'worn' (through use and removal of plaster at least) to a certain extent. the brickwork would have been struck as opposed to pointed if it were to be plastered and that would have left the surface you describe

 

[robgil]

lovely , thank you. now i have to try and decide wither or not to re-plaster it.
also , if you look at the three bricks at the right hand side very bottom , they are very badly crumbling and i was thinking of replacing them (i have 3 exactly the same good bricks) would it be a case of taking them out and replacing them one at a time or would i need some extra support?

 

[andrew gayton]

leave them.

 

[robgil]

Do you not think it a good idea to replace some failing bricks at the base of the fire place pillars?