Our house is at least 90 years old. I stripped the walls and they now are a grey, mortar (cement) looking material. Small stones fall off if I sand it. What is it and how do I seal it. I would greatly appreciate your help.
Answer:
What you're dealing with there is plaster and you should know that there is a lot of asbestos fibre (a carcinogen) in it so sanding means wearing the proper safety clothes and mask. Stripping the walls to that point means you've put a lot of work into and have taken away the plaster of paris top coating. You can either re-establish that or just put 1/2" drywall over it and go from there. My suggestion is the latter because now you can also add a 6mm vapour barrier to the perimeter walls and uppermost ceilings before do the drywall and then priming and painting.
