damp readings - help required

henpecked1

in the downstairs bathroom on the backwall neat to the extractor fan and window there is a high damp reading in the wall. Most of it is tiled (3/4 way up). Could this be down to condensation giving this high reading. I am using a hand help damp tester.

Also in the kitchen we had on the wall 1m of plaster tanked and replaced. the perimeter wasll was injected with a DPC. The new plaster is reading find, but about it, say 2m up, there is a high reading again. My only though it old damp not yet dried out or condensation from the washer/dryer, also located in that corner..

Both the kitchen and bathroom are built into an extension with 9 inch think solid walls.

Ant thoughts as we have a surveyor round shortly for our buyers

Owain_Moneysaver

Damp meters are useless. To the very limited extent that they work, they are for measuring the moisture content of wood.

ormus

almost certainly its condensation.
open some windows every day. esp in the kitchen and bathroom.
take no notice of damp meters.

David_Aldred

Hi henpecked,
Whilst you may well take a practical view to not worry about the high damp meter reading if there is nothing visible of concern and no wood in this area (that might be at risk of decay as a result of any dampness present), the fact that you are selling the property and a third party is likely to meter the area for dampness is an issue if the same high value readings are recorded when the surveyor calls.

A one brick thick solid wall is inherently prone to penetrating dampness and especially condensation within the 'wet room' enviroment of a typical kitchen. Such condensation may not be confined to simply occurring within the surface of the wall but could also be interstitial, that is to say occuring within the fabric of the wall itself. Be mindful that if the pores of the wall contain water instead of air they are colder and if they are colder the wall is more prone to condenssation such that a downward spiral of dampness can occur.

However during the middle of summer as we are at present such condensation is likely to be considerably less of a significant issue than say in cold wet winter months. Having said that in the area immediately around the fan there is likely to be a local drop in temperature so if condensation is a factor you would expect it to be concetrated within such an area as you have found.

If the plaster has been patched up around the fan when the electrician installed it the plaster may well be of a type that is more porous than the surrounding plaster / unable to hold back any contaminates from within the wall itself compounding the issues mentioned above.

Dampness emerging from the base of a wall due to true rising dampness is often limited to around 1m high although it is not unknown for it to rise much higher than this, especially if the lower areas are tiled / tanked / plastered with a hard dense plaster reducing evaporation from the wall at lower levels such that the dampness in effect jumps to a higher level. If this were the case salts may or may not be visible but I would expect if this were an issue the problem to be more uniform along the length of the wall at the new / old plaster junction rather than simply concentrated around the fan.

When the surveyor visits on behalf of buyer you might want to ask them if they found any high damp meter readings and if so where. If it is in the area discussed above consider asking them if they can do a dew point analysis to determine if the cause os indeed condensation or not. However bear in mind that the surveyor may well ask for a damp / timber report whatever the cause in order to pass on the liability for diagnosis to others / protect the buyer from suffering a loss. Hope this helps, kindest regards David Aldred Independent damp and timber surveyor