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TLDR: resistivity values and other identifying features for magensium oxychloride (Sorel) cement please.

I have a 1950s council house where the ground floor is 2 types (one room dark brown, one room red) of poured finish over a concrete slab. I want to put linoleum down, but the fitter is concerned we may have a magnesite (magnesium oxychloride cement) finish, which would cause issues with moisture.

Various sites (e.g. here and here) say you can identify magnesite by:

  • holding a small piece in a gas flame - magnesite will "glow brightly"
  • testing it using a 2-prong resistance-type moisture meter - magnesite will read full-scale even when dry (it's conductive)

I'm pretty sure the dark brown is asphalt not magnesite as it melts and burns in a flame. The dark red finish does not. If you get it hot enough it glows red (as you'd expect), but that doesn't seem very conclusive.

My question in 3 parts:

  • how conductive is magnesite? What order of resistance would I see if I measured it with a multimeter?
  • More detail on what "glows brightly" means (e.g. colour, how long does it glow for, does it brighten the flame or does the material itself glow)?
  • Any other ways of identifying it?
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  • Have you asked any of your neighbors if they've had any testing done on their houses? It's likely they were all built at the same time and with the same methods, so if they've got magnesite flooring, it's highly likely you do, too. Likewise, if they don't, you most likely don't. Also, why are you asking about the conductivity of the flooring when you say the test calls for a moisture meter? – FreeMan Nov 30 '20 at 15:08
  • the tests described in the websites are using a resistance-type damp meter as an indirect way of measuring conductivity. I don't have a damp meter but I do have a multimeter that measures up to 20Mohm. Unfortunately the near neighbours moved in quite recently! – aucuparia Nov 30 '20 at 15:36
  • I'd suspect that all the houses within a couple of blocks were likely all built around the same time. Have you all moved in that recently? Maybe it's a neighborhood revival... Don't know about the multi- to moisture-meter conversion factor, sorry... – FreeMan Nov 30 '20 at 15:48
  • Some photos of the two floors would be helpful. Especially while the flame is applied. – TylerH Nov 30 '20 at 16:54

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