Damp Proof Course and Dry Rot

clearoutkate

Hi, I'm after a bit of advice if anyone knows about these things.

To cut a long story short, we've found a patch of dry rot behind a skirting board against an internal wall on the ground floor. Floors are solid.

Initial inspection suggests that the bottom of the wall is damp, as are other walls on the ground floor - all internal.

We've been told there's two possible ways in which the damp could have been caused - poor ventilation / condensation or from the floor.

We only moved in three weeks ago (yes we did have a full survey and none of this was picked up) and the property wasn't vacant in between. There doesn't seem to be a problem with condensation but we have only been in three weeks! Three years ago a new chemical injection DPC was fitted.

Should the DPC have prevented the rise of moisture from the floor and thus the development of the dry rot?
Is there any way of telling definitively where the moisture is coming from and therefore proving who / what is to blame?

25rts

Hi

first of all lets try and confirm that it is actually dry rot. Are there strands behind the skirting board? If they are brown or black it is not dry rot. If they are grey it might be. Have the skirting boards been isolated from the plasterwork by a piece of polythene or felt as sometimes moisture can ingress during the drying period of the plaster which would lead to decay.


Keith

clearoutkate

Hi Keith, It's definitely dry rot I'm afraid, we've got brown/red dust, a smell of mushrooms, a cracked skirting board and a verification from a surveyor! We haven't taken the skirting board off yet so it's hard to tell whether they were isolated with polythene, but I'll make sure I take a look at that when we do. Something else to add to the list!

25rts

In my experience something needs to have changed to have caused the problem. Whilst rising damp or condensation could cause dry rot it is usually as a result of a leaking gutter, a slow leak over a period of time or lack of sub floor ventilation although the latter is not applicable in your case. Homebuyer’s surveyors normally cover themselves by recommending a specialist damp and timber survey this does not release them from their duty of care however and the failure to detect means a claim should be made against him or her on his or her professional indemnity insurance.

Keith

25rts

Hi Jenny,

I dont want to worry you but is the concrete that the builder has laid 150mm below the internal floor level?


Keith

David_Aldred

Hi clearoutkate,
Condensation should not be occurring to an internal wall as it is highly unlikely the dew point would be reached on such dividing walls especially during the summer months.

Identifcation and resolving the moisture source followed by drying down are crucial to controlling the decay irrespective of fungicide treatment the latter of which should only be seen as a support measure to such resolving of conditions that brought about the decay and never as a substitute. It is highly unlikely that the fungus can be completely removed from the fabric of the building without rebuilding for example if it has become embedded within masonry and therefore the aim is to control the problem.

Initial opening up to look for gaps at the floor / wall joint where dampness may be free to emerge if the floor damp proof membrane is not sealed into the wall damp proof course to give one complete barrier to ground moisture, the level of any original dpc, the level of the chemical dpc, the effectiveness of such a dpc especially if there is no original dpc, whether the solid floors have replaced original timber floors and if so why (i.e. is there a historic problem of wet oversites in the area that would then tend to concentrate its effort to emerge at the floor / wall joint with any replacement solid floors, whether there is any leakage from pipes / drains both internal and external and whether any original timber floor prior to solid floor replacement has been buried inappropriately within the sub floor void and the replacement solid floor laid on top by some cowboy builder.

Identification of the moisture source is crucial as some sources such as leakage unknown to you may be covered by your insurance and if there is a chance of them covering costs this should be explored.

Be mindful of the potential for the dry rot to affect other areas that may be remote from the current the visible problem if it has spread beneath the solid floor and this may unfortunately include any adjoining property.

The wall dpc is only there to prevent rising dampness up through the wall itself. BS6576 concerning chemical damp proof courses recommends contractors installing such dpc's address / bring to the attention of their client issues of dampness emerging at the floor / wall joint which could compromise their installation and to ensure timber is isolated from dampness.

If you have spores from the dry rot then it has typically been a problem for well beyond that when your surveyor visited in order to develop a fruiting body able to produce such spores. Given the decay that is visible and the surveyor being able to readily meter the timber skirting / base of door frames etc they may well be found negligent if they failed to warn you of the problem since they had a duty of care to inspect with reasonable care and skill of a person in their profession. Hope this helps, kindest regards, David Aldred Independent damp and timber surveyor