Cause and prevention of condensation behind drylining

Hi, I would be grateful for some advice and experience if this sounds familiar to anyone:

I have recently had internal walls rendered, tanked with k11 to a height of 1.5m (manufacturer recommendation), and clad with 50mm insulated drylining boards and plastered. This was all done by an experienced trade plasterer. However, in one room only (out of six which I have had done the same way) the floor is damp with water dripping from behind the thermal boards, all along the wall. There was not a problem before the thermal boards were added.

I am certain that water is not entering, as there are no water pipes, the room is tanked and there was not a problem before. I suspect therefore that the water is due to condensation begind the drylining boards.

Does anyone know what I can do to prevent this?

Many thanks.

You say you had the walls "tanked" . Did you have the floors tanked as well so there was a bond between floor and wall? Was the walls hacked back to the orginal brick, blocks, stone or anything else and re-rendered? And the floors dug out and a membrane put in and re-screeded? Rising damp will only be found up to 1200mm above ground level, any other damp or water ingress will be penertrating damp. How were the boards attached to the wall? If the walls were tanked properly then there should be no way that water could run down the wall. For you to see this must mean that you have not put the skirting boards on yet. Is this correct? How high are the walls above ground level that you have had tanked? And also get the plasterer back and ask him the same questions..,.

Thanks for the reply, here are the full details:

- Large old solid sandstone house. Outside ground is just below floor level. Walls are around 2 feet thick.
- Flooded by local river in 2009. All ground floor walls had plaster/render removed up to half wall height, through to stone walls. This was to aid in drying out process.
- House was professionally dried which took a long time. House was then certified dry, walls and floor. This was surveyed and confirmed twice.
- Floor is concrete on waterproof membrane.
- Rebuild: Walls were rendered and being a solid wall property, was tanked under supervision and guidance of sovereign rep. Tanking was not to solve any known damp issue, just belt and braces really while the house was being rebuilt, just to ensure damproofing is robust.
- K11 was applied up to 1.5m, because as you say rising damp does not rise much above 1.2m. The k11 was applies a good two foot into the floor. Sovereign barrier mortar was applied at the wall/floor join. A second coat of k11 was applied. This was all done to specification.
- In compliance with building regs for wall rebuild, inner external wall were faced with 50mm insulated drylining boards (Kingspan K17), dot and dab. Plastered on top. Skirting boards not yet replaced.

And out of six rooms rebuilt in exactly the same way, one wall of one room only has water "condensing" from behind drylining. Plasterer thinks it is condensation on a cold wall. I have a few ideas of how to remedy this (e.g. ventilating the wall behind the drylining), though am posting to this forum to see if anyone else has had experience of this.

Thanks for your help

Hi Gary
I am surprised that they have used a dot and dab system on the Hey'di K11. because as you say the condensation would have formed between the boards and the wall inbetween the spaces of the dots. I have used this tanking system many years ago and it is an highly effective system. I think that when there was a high risk of condensation we used to apply renderlite renovating plaster over a coat of sand and cement (2-1) made up from Hey'di bonding agent/water (1-4) as the gauging water. Get in touch with the Sovereign agent and see what he says . You should have a gaurantee on this type of work...Good Luck...