hydrofuge

[MStrell]

I was talking to a French mason who was repointing a farmhouse near ours (the Limousin type with big gaps between natural stones). He told me that his recipe for perfect re-pointing mortar was:

4 measures of white cement
4 measures of white lime
13 measures of sand
Hydrofuge (added according to instructions on packet)

He was using one heaped shovel-full as a measure. He estimated that an entire house of about 300 square metres of pointing would require about 3 cubic metres of sand.

My questions are:

1. Is 3 cubic metres of sand enough? It sounds quite modest considering how much mortar one can use in some of the bigger gaps.

2. HYDROFUGE. I cannot obtain the product he was using (Lanko 321 Lankosec, Hydrofuge de masse en poudre) and I don't want to buy the wrong thing. I have seen lots of containers of liquid hydrofuge in yellow containers at point-p and castorama. Will ANY of these products do? Are they all basically the same? How do I pick the right product and how much would be used in the above mix?

3. What sort of working time would the mix above have? there seems quite a lot of it, so I'm wondering if only any experienced mason would be able to apply that much product quickly enough before it goes off.

Any assistance gratefully received.

Thanks

[Anton Redman]

>>1. Is 3 cubic metres of sand enough?

Three cubic metres of sand will bulk to about 5 cubic metres of mortar. Assume a four sided house 15 metres long , 10 metres deep and 6 metres high. This has a total surface area of 300 square metres. Assuming the gaps are 20 % of the surface, therefore 60 square metres, this gives a mean depth of just under 17 cms say 6.5 inches. Seems about right to me.

I would start small with a mix of 25 litres say 5 galleons ( about a 200th of the materials) and work my way up as my confidence grew. You also have to move it to where you are working anyway

Somewhere on the hydrofuge packaging there will be a recommended mix. I believe they come in varying strengths.