New DPC but the damp rises higher!

[RichieWest]

Hi all. I was hoping some of the experts here might be able to help me out with a damp problem...

Situation: early 1900s house, solid brick walls with no cavity. The outside wall has a wide step up to the patio doors approx 10cm high, and is rendered down to ground level with a cement mix. Inside there was significant damp up to about 70cm above floor level with lots of crumbling plaster. Called in a chemical DPC contractor about six months ago who stripped the wall back to brick up to about 1m high, injected a new chemical DPC, lined the wall with a plastic damproofing membrane then plasterboarded and skimmed. The problem I have now is that having redecorated the room there are now large patches of paint flaking off the wall in a couple of places at a height of about 1m, above the height of the membrane, although no evidence of salts on the surface of the wall. The flaking started about 3 months ago, within a couple of weeks of the painting!

My question is, is this just the wall drying out or is the DPC failing to do it's job? The room was previously painted with kitchen paint, which formed a film over the wall. When they stripped the wall back they tore the paint film up the wall in the places the damp is showing through now, basically it appears the problem spots are where the film has gone but there is no membrane inside the wall. Should I be patient, wait for the wall to dry then repaint the damaged parts, or should I try to paint over the damage with a damp-proof paint (I suspect this may just move the problem elsewhere), or do I need to get the DPC contractor back in and accept he's going to trash the whole wall and I'll have to redecorate again?

Any advice very gratefully receieved!
Thanks.

 

[joe-90]

What makes you think he'll come back? He won't do anything extra for free - that's for sure. It's a cowboy industry.

 

[RichieWest]

To be quite honest I think I've got two hopes of getting him back, even with a "30 year insurance backed guarantee", and I probably wouldn't want him back anyway! I suppose a better question would be what do I do now to sort the wall out?

 

[roy c]

Use the 30 year gaurantee get in touch with the chemical company that gauranteed his work. I take it he gave you all the documentation for the gaurantee and you had to pay a substancial amount of money for it. If not then I dont think your gaurantee is worth anything!!!!

 

[joe-90]

The 30 year guarantee is nothing more than an insurance policy.

 

[RichieWest]

Ok so I can assume the DPC man isn't going to be returning my calls anytime soon, which is what I'd expected. Any suggestions on how to tackle the root cause of the damp and at least tidy up the interior? There are some photos of the exterior and interior here:

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• RichieWest
• 1 Mar 2013
• 1

View media item 57504

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• RichieWest
• 1 Mar 2013
• 1

Obviously the tape measure is supposed to be vertical in the last picture!

Is there any merit in raising the external render level in case it's bridging the DPC? Does the render need some kind of bead on the bottom of it in that case?

 

[dann09]

1. The "Guarantee" typically refers only to the chemicals supplied by the chemical company, not to the how or why the work was done.

All the associations and organisations for D&T work are there to make money for themselves - thats what they do; collect membership fees. The last thing that they are going to do is to annoy a fee paying member by investigating his workmanship.

So i'm told, dont go beyond small claims unless the sum involved is a min of £30,000 and you have some way of getting the money and the legal fees from the other side.

Do you have a written report and diagram from the D&T man?

2. The new eruptions might be from re-directed condensation - or various other things. Using a sheet material for "tanking" often re-directs the problem to some other area.
Ignore the paint business, "damp proof" or "kitchen paint".
Research so many recent posts on this and then come back here.

3. The RWP gulley appears to be blocked.

4. The rendering appears to be failing.

5. The patio level appears to be level with the FFL.

 

[joe-90]

Your most likely problem is a leaking pipe underground. There's a near identical thread somewhere around.

 

[Nige F]

I`m with Joe - what`s that old green iron pipe ? is it from a WC . Can you post a pic of it fully up the wall and any manhole nearby ? .

 

[Nige F]

, lined the wall with a plastic damproofing membrane then plasterboarded and skimmed. .

P/B over the membrane Just looked at www.newton-membranes.co.uk that seems an acceptable method Maybe it should have been done floor to ceiling

 

[joe-90]

Yes but if he has a leak he will get (at best) frost damage to brick faces, and at worst his house will subside and require underpinning.

 

[RichieWest]

Thanks for all the replies so far. I've done some more research and digging and I suspect that at least some of the problem stems from the patio the previous owners laid outside. I'd be grateful for your thoughts on whether I'm on the right track here. Unfortunately the site won't let me upload pictures at the moment so I've linked the pics to a web album.

Pic 1 is the back of the house.

Pic 1

As you can see, the patio step is laid quite high up beneath the doors. The green iron pipe you can see on the right is the soil pipe from the bathroom and also the vent stack. I reckon the top of the step is about 2" max below the top of the internal floor. When I pour water onto the step it flows away from the house on the left half but on the right it flows down to the right and into the gulley in front of the green pipe. On the left of the picture you can see the wall is rendered right down to ground level, and almost as far on the right behind the green pipe.

Pic 2 is more detail of the soil pipe and the gulley.

Pic 2

The base of the green pipe has a sloped concrete surround with runs away from the house. I've dug the soil and gravel out of here and the gulley has a concrete base which runs to the out from the wall as far as the end of the step. Beyond this it seems to be just soil. I dug about a 6" diameter and depth hole at the end of the base and poured a watering can full of water down the green pipe to see where it went.It flowed down the gullet and into the hole but was very slow to drain from the hole. The house is on London clay. The following pic gives you a better view:

Pic 3


Pics 4 shows the level of the step in relation to the patio doors and surrounding ground.

Pic 4

Pic 5 shows some render damage on the left about the same height as the level of the step with bubbling on the surface.

Pic 5

Note that on the left there's a red band of what seems like cement running around the house. It looks like an original feature, but what is it and what is it for? Is the DPC likely to lie behind this, or on top of it?

Pic 7 shows the side return of the house facing out towards the rear.
Pic 7



You can better in this pic the red band running around the base of the house and also an air brick whose base is at ground level. Would the DPC be running along the base of this brick? You can also see the nearest drain I have for rainwater.

So, (and thanks for being patient and getting this far!), here are some thoughts I had on what I've seen and I'd appreciate your views on whether they are sensible or just plain daft.

1) Injecting another chemical DOC is a waste of time and money and won't solve the problem.

2) The step on the patio is too close up against the wall and the drainage on top may not be adequate.

3) The rendering down to ground level is a bad idea and should be fixed. As a start I thought it should be hacked off to at least the top of the red band and finished with a bell cast. Any merit in going a couple of brick courses higher than that to allow some breathability lower down the walls? Presumably those bricks would need repointing.

4) I possibly need to either remove the patio step entirely from the wall, or dig up the 6 inches touching the wall and install a linear channel drain.

5) I need to drain the channel to a proper drain as soaking away probably isn't an option.

6) Given Q5 above, do I need to get a deep channel dug from the patio step, around the corner and into the guttering drain (it would need to be deepish to get any fall), or is there a means of tapping it into the green soil pipe?

7) It's possible the green pip may be leaking somewhere. It might be worth getting this either replaced or relined in situ.

Finally, who on earth to I approach to do this work for me? Presumably a plasterer for the rendering corrections, but what about the drainage? Is that a patio layer, or a builder, and can they tap into the existing drainage/soil pipe system or is that yet another trade?

Anyway thanks very much for reading!.

 

[joe-90]

There's another post almost identical to yours which gets wet in heavy rain.

Probably the same problem that the soakaway can't handle the high level of water and it leaks into the ground around the house.

 

[dann09]

Perhaps, scan a plan view of the ground floor indicating:
1. areas of damage and remedial repair.
2. vent positions.
3. rendered walls.
4. solid floors.
5. where the DPC course was injected.
6. positions of nearest man holes.

7. DPC injection from one side, unless double-drilled, is useless.

8. The red and black cables are not the DPC. In best practice, the DPC is located under the joist tails ie. under the air brick/vent.
It will pay you to locate the DPC.
Possibly, the red S&C plinth is bridging the DPC.
The steps are probably too close to the elevation.

9. Given, that the render is failing, and might be painted in an oil or plastic paint, then penetrating moisture could be at work. It's also possible that the interior damage was and is, in fact, condensation against a cold wall. Careful inspection of the render required.
At the least, the render has to be cut back from all ground contact and all bridging of the DPC.

10. Have you crawled under the floor?

11. Only one (3") air brick is visible.

12. Where are the Soil pipe and the side gulley draining to?

13. As above, the weird sump arrangement requires investigation.
As does the S&VP - is it leaking below ground, and is it perishing in the stack? Feel behind it.

14. Any experienced general building contractor would be competent to do the work.

 

[RichieWest]

Thanks for the reply dan. I've uploaded a rough plan view of the house here:

Plan view


It's a bit small so apologies but to answer your points.

1. The damaged area is on the kitchen wall at the rear of the house, the rough area is shaded orange on the diagram with the most damage on the leftmost wall and just some minor low level stuff running left to right into the house. The repair was done along the orange shading up to 1m height. There are pictures of the damage here:

South side damage

North side damage

2. The vent positions are shown on the plan as airbricks. There's one on the south side of the kitchen wall, east side of the lounge and two on the west side.

3. The only rendered wall is the east facing kitchen wall, shaded yellow on the plan.

4. Flooring wise, the lounge and hall has an engineered wood floor throughout which is sealed, but there is an air vent in the corner of the lounge for ventilation and the three airbricks. The kitchen has wooden floorboards but on top there is a sort of plastic lino tile affair.

5. The DPC was injected at around floor level all along the orange shading, and also up the walls in each corner.

6. Nearest (and only) manhole on the property is out the front door on the path to the street. There's a drain beneath which flows out to the street. This seems the same on all the houses here.

7. I don't know the term double-drilled I'm afraid, but they did use a geet big drill for the job.

8. The red and black cables are my Sky TV leads! It's a bit fiddly finding the DPC as the red plinth covers the brickwork (what does S&C mean please, and does that plinth serve any purpose other than being decorative?) and the internal floors are all glued in place. Short of ripping up the floor the only place I might be able to see the DPC is by opening up the lounge floor vent and taking a photo. If the original DPC is below the airbrick then it looks like the patio is just below the old DPC but the step is above, and both are below the new injected DPC.

9. The render was repaired about 4 years ago and remained in good nick for about a year before cracking began again. It's possible penetrating damp through the cracks and the join with the door frame may be at play but the damage seems closest to the door frames and seems very extensive, plus there's not that much render damage on one side.

10. Can't get under the floor, there's no access down there.

11. There's three more on the house, but only one under the kitchen floor.

12.Hard to say. I suspect the main drain/sewer under the front path, I don't know where else they'd go.

13.It's raining today and the sump at the side is damp but now flooded. It seems to cope with rain runoff OK (I think), it's only when there's a high volume of water it floods (pressure washing). SPV is sound down to ground level.

14. Need to find me a builder maybe.

Thanks for the detailed response, it's been really helpful!