On some of the older lime motared houses they used a fine pointing/grouting portland type mix to give a fillet finish around windows and doors. When removed it come off in longish strips and is very hard (cement mix ?) it seems to be made with very fine sand. House in question built between
1900-1920Anyone know what the 'mix' is ??
TIA....ttfn......Alistair
I can't say for certain, but recently I needed to set new glass into a stone mullioned window. I made up a 3:1 mix of silver sand (labeled as block paving sand at Wickes) and lime putty. Made it a lot easier to get a good finish, has bonded well to the limestone masonry and so far has proved stable.
On one occasion I also made up a mortar using building sand rather than sharp sand (all I had to hand), and used it point in a wooden window frame with quite satisfactory results. The usual sharp sand lime mortar mix can be tricky with closely-jointed masonry, so I wouldn't be afraid of trying alternatives for difficult locations. Unlike portland cement, lime mortar can easily be knocked off if there's a need to change it.
I've just mixed up a mortar that ended up about with 3.5 lime, 2 soft sand, 6 sharp sand and 1 chalk. (It's a long story). The soft sand and chalk has made if /very/ smooth and easy to push around ... and the pointing hasn't fallen out since the weekend.
I wonder if the OPs fillet is made with a) hydraulic lime; b) pozzallano's (sp?); c) Portland cement.
It could be anything, an analysis would tell if necessary. But with old soft bricks you'd do better with a lime based mortar, its now known cement mortars sometimes cause various problems with these bricks.
3:1 sand:lime is the usual mix.NT
Dear Alistair Not sure how you can tell if it is a Portland cement mix once it has set Please explain
What you describe sounds like a version of "tuck" pointing
This is usually pure lime putty and sand (open to correction here) Chris
You could test a bit. Lime once set (chalk) would fizz and dissolve in an acid (such as vinegar or kettle descaler). Cement also dissolves in acids, but very much more slowly.
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