29-08-2012, 11:17 AM
Hi Col, I wouldn't worry to much about a lime mix, personally I think it's over hyped, all the pointing I did in that barn picture was done with your standard 3 to 1 cement mix, we never had no problems with it, yes that stone fire place was a bit of a grunt to construct I picked the granite linlel up for a fiver when we first bought that place, wouldn't get much change out of one hundred quid today. We put that lintel up Eygyptian style.
There is nothing to fear about modern slab insulation in modern cavity walls, it's 2" thick and tongue and grooved, the cavity wall is constructed with a 4" cavity, they are fixed to the inner wall with non degradable clips that clip on to the SS wall ties, the clips are designed so that no water can pass by them on the wall ties, this still leaves a 2" permenant air gap between the outer face of the insulation and the outer wall of the cavity. A good builder or DIYer will lay blocks/bricks etc with very little in the way of cement droppings going down the caviity and to be really sure will hose out the cavity at the end of each shift to make sure the cavity is kept clean during the construction, any muck being washed out along the bottom and exiting through a gap purposely left in the bottom course which is filled in when the wall is finished.
I personally think that all new houses should be built facing south with a high thermal mass and incorporate plenty of glass for solar gain, ie: passive solar heating, trouble is most folks want something that looks "traditional"
As a testement to slab insulation in cavity walls: The end wall of the house we are in now was a single leaf wall being a mixture of shuttered concrete,chicken wire, bricks, cement and old paving slabs stood on end! The usual bodge up, I rebuilt this wall with block cavity construction with Kingspan slab insulation fixed to the inner leaf, I have not had time to render up the the outside of the outer leaf yet so it is totaly exposed to the rain, we have had a real battering with the rain this year with gale force winds behind it, there has been no damp penitration to the inner leaf at all, so I would say slab insulation in a new wall is good and is about the best you will get for cavity insulation.
However as has been said there will in many cases be some negative long term effects by filling an existing cavity completely with beads, foam, fibres or whatever. In my opinion the only way to improve the U value of an existing cavity wall is to insulate and clad the outside (planning problems almost guarenteed) or insulate and dry line the inside (marginaly reduced floor area)
Also if the cavity has been filled can you guarentee that no fill has gone below the DPC, if the fill has filled up the cavity from cavity bottom then I think long term there will be problems for sure due to long term capillary action bridging the DPC, the first casualty in that case will be the back of the skirting boards going rotten.
A lot of this damp proofing stuff is blindingly obvious but may not always be blindingly obvious if in a rush to show off your DIY skills, good hat and boots, dry walls and good ventilation = a healthy house, simples. As Mark has already pointed out a lot of damp is taken as rising damp when in fact it is condensation, if the ground level outside the house is below the floor level then in general any rising damp will not go up much more than 2 to 3 ft if that. When I used to do site carpentry on old conversion/refurbs etc the building regs was to damproof an old solid wall up to the 4 ft level, in the early days it was newtonite lath or sand blinded synthaproof, today a lot use thoughroseal which is really good stuff and not as messy as synthaproof. A common method today is to use thoughroseal then dry line using metal C channel studwork with vapour barrier and plasterboard. Condensation can soak a cold wall head to foot no matter what its construction is.
Good luck with the DIY/renovation Mark.
Lawrence.
There is nothing to fear about modern slab insulation in modern cavity walls, it's 2" thick and tongue and grooved, the cavity wall is constructed with a 4" cavity, they are fixed to the inner wall with non degradable clips that clip on to the SS wall ties, the clips are designed so that no water can pass by them on the wall ties, this still leaves a 2" permenant air gap between the outer face of the insulation and the outer wall of the cavity. A good builder or DIYer will lay blocks/bricks etc with very little in the way of cement droppings going down the caviity and to be really sure will hose out the cavity at the end of each shift to make sure the cavity is kept clean during the construction, any muck being washed out along the bottom and exiting through a gap purposely left in the bottom course which is filled in when the wall is finished.
I personally think that all new houses should be built facing south with a high thermal mass and incorporate plenty of glass for solar gain, ie: passive solar heating, trouble is most folks want something that looks "traditional"
As a testement to slab insulation in cavity walls: The end wall of the house we are in now was a single leaf wall being a mixture of shuttered concrete,chicken wire, bricks, cement and old paving slabs stood on end! The usual bodge up, I rebuilt this wall with block cavity construction with Kingspan slab insulation fixed to the inner leaf, I have not had time to render up the the outside of the outer leaf yet so it is totaly exposed to the rain, we have had a real battering with the rain this year with gale force winds behind it, there has been no damp penitration to the inner leaf at all, so I would say slab insulation in a new wall is good and is about the best you will get for cavity insulation.
However as has been said there will in many cases be some negative long term effects by filling an existing cavity completely with beads, foam, fibres or whatever. In my opinion the only way to improve the U value of an existing cavity wall is to insulate and clad the outside (planning problems almost guarenteed) or insulate and dry line the inside (marginaly reduced floor area)
Also if the cavity has been filled can you guarentee that no fill has gone below the DPC, if the fill has filled up the cavity from cavity bottom then I think long term there will be problems for sure due to long term capillary action bridging the DPC, the first casualty in that case will be the back of the skirting boards going rotten.
A lot of this damp proofing stuff is blindingly obvious but may not always be blindingly obvious if in a rush to show off your DIY skills, good hat and boots, dry walls and good ventilation = a healthy house, simples. As Mark has already pointed out a lot of damp is taken as rising damp when in fact it is condensation, if the ground level outside the house is below the floor level then in general any rising damp will not go up much more than 2 to 3 ft if that. When I used to do site carpentry on old conversion/refurbs etc the building regs was to damproof an old solid wall up to the 4 ft level, in the early days it was newtonite lath or sand blinded synthaproof, today a lot use thoughroseal which is really good stuff and not as messy as synthaproof. A common method today is to use thoughroseal then dry line using metal C channel studwork with vapour barrier and plasterboard. Condensation can soak a cold wall head to foot no matter what its construction is.
Good luck with the DIY/renovation Mark.
Lawrence.
