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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorFieldfare
    • CommentTimeJun 1st 2019 edited
    Hi all- I am embarking on the lime mortaring of our house and attached barn (face is prob. about 1850?). They are both faced with riven greyed Derbyshire gritstone. My new mortar looks too bright and buff and really 'raw'. The joints are actually quite wide in places and I feel that I should be pointing up to the face of the stone- not recessing. This makes the joints look really stark and new and is sort of killing the old feel of the place. I have been advised by a lime supplier to use black and yellow 'pigments' to take the edge off the colour and am now playing about with those. Could anyone guide me as to the 'correct' colour to go for? Should I try and 'grey it up' to just a little lighter than the stone? Links or photos would be super. I attach photo which doesn't really show the starkness of the new mortar but hopefully you get what I mean.
    • CommentAuthorFieldfare
    • CommentTimeJun 1st 2019
    ...and photos
    • CommentAuthorFieldfare
    • CommentTimeJun 1st 2019
    • CommentAuthorFieldfare
    • CommentTimeJun 1st 2019
    • CommentAuthorjfb
    • CommentTimeJun 1st 2019
    I'm not sure about colour but with regards jointing up from the looks of the picture with the new pointing you could do more to make sure that the joint doesn't spill onto the stone. I dont know how you are working but I would recommend a churn brush and when the mortar is no longer soft but still not dry you can bash the joints or sweep the churn brush gently over to get any excess mortar off the stone. It should also leave some of the aggregate in the mortar exposed which might darken it. A soft brush to finish can also be used after the churn brush. Best to wait till it is quite dry for that as you don't want to smear any mortar onto the stone (or onto the brush). The stones are layed with thin beds so you want to minimise the thickness of the new joint and that will help to reduce the 'new' look of your joints.
    • CommentTimeJun 1st 2019
    To match the colour better I suppose you need to change the aggregate you use to something more like the gritstone, or else simply colour the mortar with pigments as you've been advised. The old mortar looks darker than the stone, unless that is just an effect of the lighting in the photos, so I would be tempted to make the mortar a bit darker than the stone rather than lighter. If you mix a small amount initially, but carefully note the proportions so you can reproduce it accurately, then you'll be able to test it in situ and should be able to scrape it out before it fully hardens if it looks wrong. I need to do something similar wih some cracks in my render.
    All good advice so far. I think that is quite a good job work wise in the photo, and agree with you that the joints want to be filled flush with the face. When brushed off this will leave them very slightly recessed and with the aggregate showing as described above. We use a variety of hard and soft brushes - all cheap natural bristle ones from the local hardware store, some with longer bristles ("churn brush") but we do find the short scrubbing-brush type ones are good once the mortar has started to go leather hard.

    Colour wise this really is determined by the sand and aggregates in the mix. Sharp sand and soft sand from different places (e.g. between different big DIY sheds) can end up with different shades of mortar. You can use red or yellow soft sand, it looks like you have used yellow which is what I would go for on that stone. Red sand would give a pinker mortar which looks good against red sandstone.
    The old mortar looks dark or grey in the pictures but in reality this is just dirt and weathering. If you look at the places where it is more full the mortar is quite light. Pick a big chunk out and look at the back of it, break it open, see what the colour is then on an un-weathered part.

    The whiteness will fade after a year or two, I wouldn't stress about it. It is an honest repair.

    Tools haven't been mentioned yet, a mortar pick is a useful tool. I also like old bits of pointy metal for scraping awkward bits.
    I agree with Dominic. The repair you've done looks good, and will weather fairly quickly.
    I use the sharp sand/concreting sand from the local builders merchant which comes out slightly greyer than your sample.
    I also tried the sharp sand from travis perkins and that came out quite a bit more yellow. May be worth getting a bag from all the local builders merchants and trying them all, as depending on where they're sourced, they'll all be slightly different colours.
    Personally I think adding pigments is the wrong way to go. Use what's local to you and keep the repairs honest.
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