New Damp Proof Course

[chairmo]

I've moved into a new flat, which is the downstairs of a terrace.

Before I moved in a new DPC chemical injection was installed, at my request after a survey, to about 1/3 of the bedroom walls.

Near to the corner, where the new DPC was installed, there is alot of damp and moisture coming through. From the skirting board to about 12 inches up.

Is this normal, is it just the new DPC settling in, or do i have a problem and need to get the contractors out to look at it?

 

[foxhole]

The damp course was probably not needed, the penetrating damp problem needs curing before any other work, simply replacing a dpc cures nothing.

 

[chairmo]

How can you tell the difference between the two?

Would it not be more likely to be rising damp if the damp is at the bottom of the wall. There is no drainpipes next to the area in question.

 

[oilman]

How can you tell the difference between the two?

Penetrating damp comes from an identifiable problem, rising damp does not exist.

 

[chairmo]

Thanks for the responses by the way.

The damp seems to have receded for the moment. I don't know if this is a good thing or not.

It was funny how the damp was not above 12 inches up the wall, the skirting board was damp, there was no black spores, there is no rainwater goods directly next to the damp patches.

All of which would suggest rising damp.

 

[JerryM]

Damp is not an easy thing to sort. You need to be sure of the cause before remedy.

I would get the contractor back to get his thoughts.

The advantage of injection is that it is immediate. It floods either the mortar or the bricks with liquid or cream which block water travelling up the brickwork (damp can be upto ~1m above ground). After injection the wall should have been rendered. This render can take some time to dry out particularly during winter. It should not come & go however. There is clearly still something wrong.

The 1/3 of walls may be an issue. The walls which were not treated should have been isolated to prevent bridging. This involves injecting vertically at the ends of the chemical DPC.

The render/plaster should have been stopped short of the floor again to stop bridging (typ 25mm).

Often cavities got blocked during construction (by mortar falling) which can bridge the DPC.

You do need to rule out penetrating damp (coming from outside and bridging the cavity). Were the external walls injected? The injection should be a min 150mm from the ground and should align horizontally with the injection holes in the inside walls. There could be a cracked drain - to be sure try to workout the route of the drains and ideally dig out gently adjacent the area of damp to be sure.

I would get your original contractor in then get a 2nd opinion. If you can build a better picture of before and now then it might prompt a few more ideas.

Damp readings will be affected by rainfall and differ in winter and summer. eg a wall may be dry in summer but damp in winter.

 

[MarkNewman]

I'm a building surveyor but need more info to offer advice.

- When was the flat built?
- Is it a purpose built block of flats or a conversion?
- Solid or cavity walls? (if cavity are they insulated?)
- Solid or timber floor?
- what's the difference in height between the outside ground and internal floor, and where's the original and chemical DPC in relation to both?

 

[hotrod]

How can you tell the difference between the two?

Penetrating damp comes from an identifiable problem, rising damp does not exist.

Rubbish. Suggest you do some reading into capillary action of moisture through brickwork.

 

[noseall]

please click me

 

[anobium]

How can you tell the difference between the two?

Penetrating damp comes from an identifiable problem, rising damp does not exist.

Rubbish. Suggest you do some reading into capillary action of moisture through brickwork.

Forget it hot rod ,your more likely to convince this lot of perpetual motion than you are of rising damp.

 

[chairmo]

I'm a building surveyor but need more info to offer advice.

- When was the flat built?
- Is it a purpose built block of flats or a conversion?
- Solid or cavity walls? (if cavity are they insulated?)
- Solid or timber floor?
- what's the difference in height between the outside ground and internal floor, and where's the original and chemical DPC in relation to both?

Thanks.

1. 1930s

2. Purpose built terraced house with one self contained flat upstairs and one downstairs. Quite common in Tyneside where I live. I'm downstairs.

3. Solid walls.

4. Timber floors.

5. I'm not sure how i can check this?

Not sure if there was an original Old type of damp proof course in. The affected walls have had two treatments of chemical dpc in the past 15 years or so. The first one apparently was defective as it did not cover all the wall area that was affected with damp. The second treatment was the one just before I moved in.

I have the documents from both treatments so i can refer to them (when i dig them out) and tell you where the dpc was injected?

 

[hotrod]

Well for those that think rising damp doesn't exist and can't accept that water can, and indeed does, travel vertically I can suggest they read, "Water transport in Brick, Stone and Concrete" by C.Hall and W.D.Hoff - Spon Press (2000) ISBN: 041922890X. The Building Research Establishment also has various useful papers / articles on the subject.

Rising damp is basically caused by water being 'sucked' up through the pores in the building fabric - a very crude explaination with many variables I admit. Therefore, a building with a suitably installed dpc (which by it's nature is non-porous) will not suffer from rising damp as long as the dpc cannot be 'bridged'.

 

[Softus]

How can you tell the difference between the two?

Penetrating damp comes from an identifiable problem, rising damp does not exist.

Rubbish.

You seem very confident of the existence of rising damp in brickwork.

Would you mind answering a question about it: if it happens so easily and frequently, why have only two people on this web site, to my knowledge, ever, out of all those who've argued, written and read about the subject, been able to describe a real-life example of rising damp that they've seen with their own eyes?

 

[chairmo]

5. I'm not sure how i can check this?

Not sure if there was an original Old type of damp proof course in. The affected walls have had two treatments of chemical dpc in the past 15 years or so. The first one apparently was defective as it did not cover all the wall area that was affected with damp. The second treatment was the one just before I moved in.

I have the documents from both treatments so i can refer to them (when i dig them out) and tell you where the dpc was injected?

Oh, the internal floor is 7 inches above the outside ground level.

 

[Softus]

Oh, the internal floor is 7 inches above the outside ground level.

In that case you've wasted the money you spent on the DPC company, and exposed them as charlatans.

I would sue my surveyor if I were in your position.