Hoping to bounce a bit of a dilemma off you kindle people and perhaps get some fresh perspective. We're currently putting in a flat roof for my kitchen extension and are cutting the wall for the trays. However the previous builders have inexplicably used thermalite blocks for the outside course and when trying to cut through the blocks just drop away from the render (the render seems like it hasn't stuck and is only gripping on the perps. Currently I've just wedged some blocks in there with expanding foam to hold it for now while I think of a plan - anyone got some ideas? Essentially I can cut the render away for the lower section but am afraid more blocks will drop, and I want to avoid having to redo the entire wall because it could become the entire backend of the house. Photo attached which doesn't show much but hopefully helps - you can see how the render has come away from the block and this entire block just fell out.
