What do you mean? Floor is rock and soil with some gravel at the moment. Its is only a cave not a room to live in, just a bit of storage and a freezer.
Thats what I was thinking about. I had just hoped to reduce the dampness, the wall is half outcrop and half stone built up to a level. Its not waterlogged just infill on the outside but I guess rain permeates down and eventually through the wall.
To think this all started with the missus wanting a new bookcaseā¦
I leaning towards thinking Iāll add a bit of hydrofuge and ciment to my lime mortar and render/point the back wall.
1 Like
Hi Patrick, I canāt help think that the first job should be to remove the back-fill against the outside of the wall. A simple French Drain (no pun intended) could lessen the symptoms and therefore reduce the cost of the cure.
2 Likes
In the UK you would always wrap the ends of joists going into a potentially damp wall with damp proof membrane. Doesnāt seem to be done here as a rule but still seems to make sense to me.
Have wrapped the ends of the joists we put in to a cottage to replace the old ones that had rotted off where the joist met the wall.
Only been a couple of years since we did that so canāt actually tell if it has helped, the old ones probably lasted 100 years, but they were hardwood, not softwood like the new ones.
Echo otherās comments on chaux versus ciment. Chaux every time. Check the NHL number, for the job youāre doing I suspect you should go with NHL 5 (thatās the choice of our stonemason who does know what heās doing.) The lower numbers make a weaker mix.
1 Like
Ray is right, a French drain helps if itās easy enough to fit in
Lime lime lime, no cement whatsoeverā¦ e.g. This http://www.lime-mortars.co.uk/lime-mortar/hydraulic/NHL3.5
And air is a huge help, (air brick s perhaps) will help prevent mound and dry rot
I wouldnāt go near trying to coat or cover the stone, as air will keep it dry and smelling well
A bit of plastic damp course tween the stone work and the wood beam resting on the stone will help prevent rising damp getting to the wood
Bill
1 Like
Actually, replying to my own post, I should qualify the remark about NHL rating. The goal is to ensure the mortar is softer than the masonry (thatās why cement is not a good idea in many situations, the cement mortar is less flexible than the masonry so the masonry breaks, not the mortar)
Lime mortars can be of different āhardnessesā. Lower NHL numbers are a factor in creating āsofterā mortars, higher numbers lead to āharderā mortars. NHL 5 is therefore at the hard end, my thought being that was good for creating a firm bed for the joists. However, if the stone is soft, then a softer mortar would be the right choice.
1 Like
Just following this discussion on Lime versus Cement OPC
Main problem with cement is not Hardness as this can be adjusted by adding Lime and varying the mix Ratio
The problem is the salts / sulphates which attract moisture and cause damage to the host masonry
Also NHL Nos 2 3.5 5 are only very basic indicators of the strength after 28 days in a standard test
The reality is a 2 from one maker can set harder than a 5 from another after 2 years or less
The Standards for Lime EN 459 are only guidelines
A lime spec has to be specific to a Maker the one nearest the standard is St Astier see www.stastier.co.uk for english specs
On old buildings only use NHL marked products not HL or ZL as these contain Cement and or other additions
1 Like
Great -----Thankyou Ed and Tim ! TERRY
The problem is that half the length of outside of the wall has been concreted over. I could dig the other 5feet deep out and fill with gravel I guess
Hi Patrick,
You could always cut a gutter type channel in the concrete so that it drains/directs any rain into your trench of gravel - this would save the task of removing all the concrete.
For the gravel trench (french drain), you could use a permeable pipe at the bottom. This will allow the water in and can then also then take any water away from the building if you have a gentle fall on it.
If you do go for the removal of the concrete then I wish you good luck, weāve been cutting out and breaking up a re-inforced concrete floor and itās not for the faint-hearted !! The breaking with a 16kg demolition hammer and shovelling 50 big wheelbarrow loads of rubble were the toughest bits.
Iām still trying to prepare myself mentally for cutting out two more 5m runs for new soil and waste pipes, At the moment Iām telling myself that I have a double saving; not paying someone else to do it and not paying to get the same exercise at a gym 