is the damp back?

TBeckett100

Oct 08 we had the damp people in to tank, chemical dpc and replaster the walls to 1m.

We employed a handyman who screwed back the skirting boards which I am assuming is going to cause problems and may have to lead me to suing him if I can prove he was at fault for damaging the tanking.

This morning i discovered a lumpy patch of plaster which i can almost put my finger through. There is another area of the other wall that has a brown tinge and in the kitchen about 1/2m up the wall the paint has bubbled up in a line which feels salty underneath,.

Any ideas?
and what stuff can we inject in the screw holes to seal the tanking again?

maninthestreet

If the scews holding the skirting board to the wall had compromised the the damp-proofing work, you would expect the signs of damp to appear at the skirting board level, not 1/2m up the wall.

Mankysteve

i would agree. Is the damp actually caused by raising damp or could it be something else such as rubble on the wall ties, blocked air vents ect sure they damp proffer would have given you a guarantee phone them they'll be the experts.

David_Aldred

Hi TBecket100,
Your description of being able to put your finger into blisters to the plastering system suggest partial failure and sometimes moisture evaporating from the wall will leave behind salts previously held in solution that accumulate and crystalise out thereby disrupting plasters at the point of crystalisation with a similar problem occurring to tanking systems that are breaking down.

Tanking is a phrase often used to describe modified renders and slurries that are designed to hold moisture back at the point of entry, though they have no structural integrity of their own such that they rely entirely upon the soundness of the substrate to keep them in place. Typically used in basements with the damp proof course ideally 150mm above ground level. Sometimes tanking is also used above ground level to areas where it would be difficult to resolve penetrating dampness.

Your description does not make it clear whether the areas of concern are above or below ground level and at what level the remedial damp proof course (dpc) has been provided in your case.

If the tanking is holding back moisture under hydrostatic pressure then yes drilling through it to insert fixing plugs for skirting is like putting a pin into a plastic bag full of water and leakage will occur.

Are the tanking and dpc works covered by guarantee? If so you need to write to the contractor who undertook the works and explain the problem to them in order for them to re-inspect and comment upon the situation. If you simply attempt corrective works without informing the remedial treatment contractor you could invalidate the guarantee if one exists.

Hope this helps, kindest regards David Aldred Independent damp and timber surveyor

TBeckett100

Thank you
When we bought the house the surveryor picked up high readings on all walls. To the rear of my property is next doors garden and it is higher up the wall. On this wall it will be penetrating damp under pressure. The blistering is occuring on the front wall. We have a french drain and the dpc injections were done at this level. The damage i refer to was above the nailed skirting and above the chemical dpc.

TBeckett100

David_Aldred

Hi again,
Thanks for the photo and further explanation which makes sense of why tanking was used in that situation. Things are never straight forward I know but things perhaps to bear in mind are:

You employed a specialist contractor to resolve dampness and it is they who have deemed what was appropriate in each situation they found at that property to resolve that level of unwanted dampness such that the property would be expected to dry down to a level that was perceived to be dry. If they undertook the re-plastering / tanking then that should be undertaken with reasonable care and skill such that it is appropriate to hold back salts and moisture within the wall for the period of guarantee.

If floors are solid there needs to be careful attention to the floor / wall joint which is the weakest point in the structural waterproofing system given the floor will tend to move seperate to the wall and the specification used to resolve the dampness needs to cope with this eventuality.

If floors are of suspended timber then the sub floor conditions should have been investigated by the contractor and if found to be contributory to the dampness they should recommend resolving those conditions or recommend alternative floors.

I know french drains next to house walls are common but they are not ideal as they tend to act as a sump collecting rainwater from surrounding paths / driveways and direct that moisture into house foundations / sub floor voids. If ground levels are high and cannot be reduced to 150mm below the dpc and slope away from the property then modular trench drain systems such as Aco or similar are preferred discharging into appropriate below ground drainage systems ensuring interfaces with house / drain / paths are sealed with flexible imervious material that will accomodate differential movement.

Taking legal action against the joiner for drilling through the tanking depends upon what their instructions were from yourself, whether it was reasonable that you should have warned them of the risk of puncturing the system and whether they would be deemed to have sufficient knowledge to be reasonably aware that what they were doing would compromise the structural waterproofing. It should be obvious that the joiner is not expected to be an expert in dampness and as such there is a different duty of care owed than say that which is expected from a dpc specialist contractor puncturing the structural waterproofing. I have known carpet fitters do the same thing and their company have paid out for resultant damage but in that case the dispute never reached court and was settled as a gesture of goodwill by the carpet company.

There are products to the remedial treatment specialist which you should be able to purchase specifically designed to seal service penetrations through structurally waterproofed walls (contact details available upon request) and the manufacturers of those products will be pleased to advise but as indicated in the previous post if it were me then my first call would be to the remedial treatment contractor who guaranteed the work to have them re-inspect. From what you have described and the photos you have posted there is a risk that the problem may well become worse / more extensive over time so it should be addressed sooner rather than later especially if timber is damp and at risk of decay (especially dry rot) / increased risk of wood boring insect attack from those insects that prefer to feed from damp decaying timber. Degrading plaster will not recover once it becomes contaminated.

Hope this helps - kindest regards David Aldred Independent damp and timber surveyor