[shygirl]

Does anyone know how to water proof an existing wall that is wet? preferably DIY.
Iv heard that you can spray the walls with something but I don't know what.
it involves a converted steading.
we have 2 walls - one is a solid granite 100 yr old bothy wall that is part of our house and appears to have no damp membrane as you can clearly see the granite blocks in the ground. this wall has a chimney stack in it and gets visibly wet during the winter and leaves tiny puddles inside if the fire isn't used. this wall is harled on the outside and exposed on the inside.
- the other wall is used as a garage and is the only section of our steading picked up by surveyors as being damp. it is externally harled (visible wet patches on the outside and damp to touch on the inside) and I believe it is concrete block construction with inner plaster (though most fell off during a bad winter), but could be granite.
the harling has been failing (falling off) for the past few years so isn't waterproof.
our neighbours (part of the original farm) had a similar problem in their farmhouse and they had builders round to remove all harling, point and its now exposed stone on the external side. this took along time so I presume it was an expensive job, so im looking to do something myself. its mainly single story.

any tips? thanks

[Victorian Farmer]

To do it cheap I would get some roof batons fit them get a rock wool insulation and board whith the plaster board whith silver one side .Fill gaps and that's it cost under £100 . Iv been to some damp places and this works .

[shygirl]

sorry I should have said, I was looking to waterproof it from the outside as I love the look of the natural granite wall.

[Backinwellies]

Old stone walls are meant to breath ... water proofing them just sends the damp inside (my living room wall is a good example!)

[Somewhere_by_the_river]

Backinwellies is right, we have the same problem where the stone farmhouse has been rendered in concrete, stopping the wall from breathing naturally so the water comes in instead. Do you know what the 'harl' is comprised of? If the bothy is only 100 years old it could well be concrete, not the breathable lime it should be, which would cause the problem. They did try some form of 'tanking' on the interior walls here, but all that does is force the water out higher up, above the treated area. Sadly no chance our landlords will pay to have the exterior stripped and re-rendered with lime and it's not really a DIY possibility (apparently)... 

[shygirl]

the harling put on 20 yrs ago and its granite chips with a pale "concrete?" possibly lime? - at the very base of the bothy wall there is no harling, just big granite stones.
we have lost a lot of harling in other sections of the house as water has got behind the harling and froze, which we have patched up ourselves with concrete.

in regard to the garage section, would being wet mean this be missing something as it isn't part of the actual house although its still part of the same steading.

if I left it all as it is, is there any long-term damage occurring?
thanks

[oor wullie]

If it was harled 20 years ago it is most likely concrete.  It is common to use snowcrete cement for harling which, depending on the sand used, can give anything from a grey to a brilliant white colour.  Most white houses you see are not whitewashed but harled with white cement.

The walls are probably built with the big granite blocks facing out and the inside of the wall filled with small rubble / packing stones.  If it is lime mortared, water getting inside the wall can start to wash out the lime.

Before going for serious repairs check that rain is not coming down the chimney causing the dampness.  I have seen this a couple of times and solved the problem with a £20 cowl.

[bigchicken]

Get a few experts in to get there opinion, this should be free advice and go from there. What you don't want to do is make a repair which does not work and will waste your money. Dampness in older stile building can be a nightmare.

[honeyend]

I agree that its probably  not breathing, modern ideas can be the worst thing for old houses. The idea is to use traditional finishes to let the house move the water out through the walls, if you look on heritage property maintenance sites they give good information
.http://www.brianfranklin.co.uk/CT%20Damp%20Proofing.html

[shygirl]

many thanks, I will look into it 

[mart6]

http://www.thompsonswaterseal.com/waterproofing-products/multisurface-waterproofers/

Try this  spray it on after the exterior wall has had a spell of dry weather then repeat 7 days later.
You can use a normal garden sprayer but wash it out afterwards

If you can it would be worth giving it a coat of masonry paint afterwards prolong its weather resistance but not essential.
Put a dehumidifier inside the room for a couple of weeks

[shygirl]

that must be what I was told about, thank you so much!

[mart6]

If you carnt find it Wickes do own brand similar product prob made by same people
http://www.wickes.co.uk/Wickes-Water-Seal-For-Vertical-Exterior-Surfaces-5L/p/600336

You can brush them on but it wastes lots far better to spray it on as its  water like consistency

This is also worth a look
http://www.sovchem.co.uk/profile/news/read/id/190/

[regen]

wall with chinmney- check out that chiney and fit cowl first particularly if only wet when rains. With the other wall the problem may be lack of heat which changes dew point and is causing thecondensation on inside of wall.

I have an office in a large stone barn with 26 inch stone walls with rubble soil infill which was pointed using cement not lime mortar many years ago. Internally it is fine -no damp where the walls have been battened and plasterboarded but the chiney stack is solid stone with cement and if the office is not used this sweats due to condensation from the air inside. If the WBS is lit and /or during the summer it does not get wet even during periods of heavy rain.

No damp (other than that caused by leaking chimneys) on house in last 12 years where the 26 inch stone walls have been rendered with cement and we get driving rain at 800 feet. Again no damp proof membrane but internally battened and plasterboarded about 20 years ago. Internal temp aintained at about 20 degrees and RH usually around 60%

Look long and hard before applying any waterproof coat to the outside.

Regen

[Womble]

Hmmm, we have a similar problem at one end of our house. It's been battened and plasterboarded, as mentioned by others. However, we have white mould growing right round the skirting board on all outside walls, and if you leave anything on the floor, the carpet goes damp and mouldy underneath.
 
My theory is that the mortar has been coming away from the inside of the walls and has fallen down behind the skirting board. This then forms a damp-bridge between the exernal wall and the skirting board, and so makes the plasterboard damp, which is causing the mould. I think the problem with the floor is that no air can circulate beneath the floorboards and out, because the route is blocked by the fallen mortar.

So, for those of you who have seen this problem before, does this analysis seem correct, and if so, how much of a ventilation gap should I have between the ends of the floorboards and the wall?