water droplets on stones

[Socksitis]

Inside the old house is an internal wall, granite stones, with cob used as the infil as opposed to lime on on the other walls. On this particular wall the other side is stone faced, internal - like a barn, with lime render as opposed to the cob. The length of wall is about 4.5 metres, with the middle section of about 4.2 metres being of the cob infil and the ends being lime render.

Now on this wall there are water droplets on the granite stones. There is no water ingress. The ends of the walls and indeed the rest of the room do not suffer from this water droplets on the stones.

Why is it there and what is happening? Is it some hygroscopic tendency of something? (excuse spelling but water attraction is what I am trying to say) suggestions please, as I will need to understand what is going on before I lay electrics and lime render over the wall

 

[Flyfisher]

Condensation?

 

[Socksitis]

No, not condensation because it is very specific to this one wall and the main section in the middle, excluding the end sections that have a lime mix between the stonework as opposed to this section with the cob infill between the stones.

 

[Abi Cott]

Condensation can be very specific. It can depend on airflow patterns in the room, the placement of heating devices and the variation in natural heat retention of different materials.

 

[MikeG]

Are the other surfaces in the room all plastered/ rendered?

 

[Spoilt Victorian Child]

Is it a lot of water? Is it always there through all seasons? At what height does it appear?

If there are no leaks, and the other side of the wall is dry, I can't think it could be anything but condensation? Where could water be coming from?

Does condensation form on the windows in that room? It tends to form on the coldest aspect of a room. A quick way to test/rule it out would be to hire a thermal imaging camera. If that section of the wall is the coldest point in the room, it's likely just condensation.

 

[CliffordPope]

If some stones go right through the wall, for strength, then they will be the cold ones attracting localised condensation on the inside.

 

[Socksitis]

There is no condensation on the windows as there is so much air movement - two panes of glass missing at either end of the wall and the room is so big. I see your point about the stones going through the wall being colder - yes it is possible that these stones and this wall is colder - I have a thermal camera so will have a look.

As to what it could be, I can only hazard that there is something hygroscopic about this wall and something is attracting the droplets - like fertiliser attracts moisture and salt.

It is very interesting, but at the same time I wonder about putting lime plaster on this wall until I can understand what is going on.

 

[Flyfisher]

The results of thermal camera imaging would be very interesting to know.

As for hygroscopic substances, my understanding (and I'm stretching my school chemistry memories here) is that such substances do indeed absorb moisture but that the moisture becomes chemically bound to the hygroscopic substance itself, ie it wouldn't result in droplets of water forming. Think of something like silica gel, which is often used to keep electrical/electronic products dry inside their packaging. It does this by absorbing any moisture itself, specifically to ensure that water droplets do not form anywhere else within the packaging. As far as I'm aware, granite itself is not hygroscopic and I don't understand how a nearby hygroscopic material would attract water to form droplets on a nearby granite stone rather than directly absorb it itself and thereby take it out of circulation.