Unwetable ... mortar/sand?

Hello all, im in a spot of trouble. After a simple Wood burner change got out of hand, im presented with a meter square hole in the wall where a "Cornish range" once was fitted. It looks to have been a bit bigger than the hole but the 1970's builders only had a short lintel so they built a brick peer to support one end, out of any old rubble bricks and dust they could find. That left a sort of "round the corner" cavity which was behind and hidden with our old stove. the back wall is granite, bricks, and some lime mortar and a mystery fine grained reddish sandy mortar. I have screeded most of the back and sides after having sprayed a fixing solution on the dry bricks. But the reddish stuff seems to be totally dry and unwetable. The surface dampens and rolls out immediately exposing more powder! I gave up brushing tried spraying....i dare not dig too far back and trying screed on it just saw lumps rolling out... what is it and how do i deal with it?.

try wetting it with a dilute mixture of Unibond and water. the more watery it is the better it soaks in. On a difficult surface, you can keep applying it with a soft paintbrush each time it soaks in.

Once stable and dried, apply a couple of coats as recommended on the Unibond pack for screeding.

(or other PVA builders adhesive)

JohnD said:

try wetting it with a dilute mixture of Unibond and water. the more watery it is the better it soaks in. On a difficult surface, you can keep applying it with a soft paintbrush each time it soaks in.

Once stable and dried, apply a couple of coats as recommended on the Unibond pack for screeding.

(or other PVA builders adhesive)

Click to expand...

yes tried all that, the brush just pulls the dust out and it rolls down. Thats why i tried spraying the solution from a kitchen spray thing. It just wetted the topermost surface which then rolled out again...ive sort of decided its never going to be stable enough to screed and needs digging out!

would it be possible to build a wall in front. just a suggestion

wsdconst said:

would it be possible to build a wall in front. just a suggestion

Click to expand...

Well they way i "fixed it" was... dug as much out as i could. Sprayed the remaining with car spray paint primer, in lots of very thin mistings. that was the only way i could get it to "fix" at all. I then put mortar in the dug out holes and screeded over it all...i put a scoop full of the powder in a bowl of water, it flaoted til i gave it a stir, then it sort of sunk and just stayed not wet even when i left it over night!... it was like coco powder! I cant blame the 70's builders this time though, it looks far more ancient than that posible from the 1800's when the house was built.

Thanks for the sugestions.