Duke147

Hello all, we are a few years down the line from the start of this topic, but I found this thread very pertinent to a project I will soon be taking on hopefully, if the purchase goes ahead. My issue is a listed building with suspected solid walls (no cavity) and within green belt. The quoted post above by Cpd seems to my mind to be "my preferred solution" after my limited research and it is by no means the only solution. There is a great document on this situation by Historic England HERE btw. It defines what the original poster has been hinting at all along in his replies to others, and that is the long to very long term potential hazzards of fully waterproofing the inside without paying attention to the external wall which nobody has yet paid the correct attention to in my opinion. But, Cpd has pointed out a way of mitigating the ground water and the salts that could harm the external wall over time and it seems to make sense to take the ground below the slab as low as possible or as low as required, so as to aid the dispersion of water at the base of the outside wall. Cpd pointed out the mistake of capping off with cement at the wrong stage, so future readers should take note. It would be nice if @Cpd could update the forum as to his solition working if he is still about? As for the 50mm perimeter with pea gravel, my choice would be PIR board cut into strips to shutter off the perimeter/outside wall, prior to pouring concrete to the required height. This shuttering will break the cold bridge between slab and outer structure. So my build up of floor would be something on the lines of:- *Install french drains to the full perimeter to a height below the internal finished floor level *dig out original concrete floor to depth to be determined *Insert perforated drainage pipes of 4" or 6" running away from th property (downhill) *Take those pipes beyond the external wall that they fall towards if possible (and into the external french drain?) *Lay large golf ball sized hardcore base over the perforated drainage pipes *Lay a softer edged product to protect DPM from being punctured ie builders sand *Lay DPC and take it well up the walls ie minimum of 1m (I believe rising damp cannot rise over 1m) *Lay correct depth and type of under slab insulation *Lay concrete pad to correct thickness From there, I will consider further on weather to install a cavity or not between the external wall and insulation to the inside walls depending on what I find during investigations. I will also revisit the Historic England document several times to consider the options mentioned, and as they say, it may well be a hybrid approach which may depend on which elevation faces the differing climatic conditions.