Another damp issue...avoiding DPC?

[Enazza]

Hi all, i would appreaciate any advice you have in helping me find an alternative to tanking & insertion of a chemical DPC.

I've gathered from reading this site that generally, the use of chemical DPC is to be avoided when it comes to period houses. We've had a full building survey & 2 (supposed) damp specialists surveys, all of which came to the same conclusions - rising damp (I know that many disupte whether this exists), which should be treated by DPC & tanking.

A bit about the house - it's a 3 storey mid-terrace, approx 110 yrs old. It is south facing, situated on the north side of a hill with the ground sloping steeply to the rear. The lower ground floor which occupies the rear half of the building footprint is completely below ground level at the front, but less than 0.5m below garden level at the rear.
To the front of the building above ground level is the bay window to the front reception, to the rear of the building above ground level is a 3 storey annexe. There are obvious signs of damp at lower ground level - indicated by warping of the lining over the earth retaining wall & high moisture readings when the survey was carried out.

Specifically, the damp specialist report recommended
1) tanking of the earth retaining wall in the lower ground floor
2) insertion of a DPC to 1m & internal damp course replastering to the rear annexe walls

I'm not technically up to scratch by any means, but noticed several points in the Building Survey that indicate insufficient ventilation

"...the front wall of the building has ventilation grills for sub floor ventilation, plus below the entrance porch tinto the cellar below. However this appears to be blocked up from within the cellar.....we noticed ventilation to the rear elevation to air the sub floor at ground level or within the kitchen wall at high level......we note that the lower ground floor is ventilated in the kitchen, but the first floor is not adequately ventilated to the rear - we recomment that sub floor ventilation to the sitting room be provided by inserting ventilation holes into the cellar below the kitchen, or ventilation grills be provided into the rear external wall of the sitting room..."

I'm interested to know what your opinions or recommendations are. If we increase ventilation could this be enough? What would the consequence be if we did nothing?

Also can anyone recommend any PROPER damp specialists around South East London? & any idea how much I should expect to pay for a damp survey?

Many thanks
Natalie[/b]

 

[MdB]

rising damp (I know that many disupte whether this exists),

I don't think there is much debate about the existance of rising damp. I have it in my house. (Queue lots of people telling me I'm wrong). Note however, it rises a maximum of 300mm (ish -I am sure I read this somewhere - depends on lots of stuff - see Matts comment below) so damp half way up the wall will not be rising damp.

which should be treated by DPC & tanking.

I think that is where the debate is - most here will say that this is not the solution. My damp has had two tanking attempts in the past both of which have failed badly. The better solution is to remove the cause of the damp in the first place if possible. In my situation this means lowering the water level by lowering the ground level outside the house and by the addition of French drains.

In your case, improved ventilation will definately help. Last night I removed a damp cupboard from an alcove to get at the dry lining behind. One section was ventilated and was fine. The other section was not ventilated and was covered in damp.

 

[Matt Green]

rising damp (I know that many disupte whether this exists),

I don't think there is much debate about the existance of rising damp. I have it in my house. (Queue lots of people telling me I'm wrong). Note however, it rises a maximum of 300mm (ish) so damp half way up the wall will not be rising damp.

It's a question of defining the term more than anything.

Where do you get the 300mm figure from? Water can certainly rise higher than that in a plastered wall. That's why you see salt bands at 1m up walls with bad ground levels or poor drainage at the base.

Matt

 

[Matt Green]

In your case, improved ventilation will definately help.

In as much as it won't be part of the problem, yes. The rooms with the earth retaining front wall of the lower ground floor are likely being used for something they were never intended. There is a constant supply of ground water into it and it will never be dry.

You can line it or tank it. Tanking it is determental to the building in the long term as it bods to the brickwork and will spoil the faces when removed. You may or may not care, if the building is listed, the CO might. You will also need to tie the tanking into the floor structure somehow.

If you line it, strip the wall to the masonry first and use isolated timber or inorganic fixings.

As for the rear wall, try and lower the ground levels to at least 6" below the internal floor height, or continue the lining round if that's not practical.


Matt