Sanity check on builder quote for floor levelling and DPM installation

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Following on from another thread I posted recently, I’ve had a builder out to quote for the levelling and damp-proofing of my bitumen adhesive covered concrete floor. The damp levels in the current floor are marginal; some areas showed green on the builders damp meter, and others yellow. I’d prefer to err on the side of caution, and get a fresh DPM laid so I never have to worry about it again.

The builder has quoted for applying 2 coats of Everbuild Black Jack, followed by a layer of Arditex NA. I have a couple of concerns about this however. Firstly, I‘m not sure if it’s a good idea to mix products from different brands. My understanding was the recommended approach in my situation is the “Ardex Sandwich” with a thin layer of Arditex NA, their DPM 1C, then another layer of NA.

My other concern is I believe there is approximately a 2cm drop in the floor from one end of the room to the other, which I’ve worked out using a combination of laser and tape measures:

3748A6B2-5767-487B-9DD9-93D231D4FB13.jpeg


Based on this, I’m struggling to see how either a) their 3mm layer is going to make any meaningful inroads in levelling the floor, or b) how the DPM sandwich could work, given I understand that even though Arditex NA can work at higher thicknesses, the layers need to be quite thin when applied on top of bitumen, and again on top of their DPM?
 
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Following on from another thread I posted recently, I’ve had a builder out to quote for the levelling and damp-proofing of my bitumen adhesive covered concrete floor. The damp levels in the current floor are marginal; some areas showed green on the builders damp meter, and others yellow. I’d prefer to err on the side of caution, and get a fresh DPM laid so I never have to worry about it again.

The builder has quoted for applying 2 coats of Everbuild Black Jack, followed by a layer of Arditex NA. I have a couple of concerns about this however. Firstly, I‘m not sure if it’s a good idea to mix products from different brands. My understanding was the recommended approach in my situation is the “Ardex Sandwich” with a thin layer of Arditex NA, their DPM 1C, then another layer of NA.

My other concern is I believe there is approximately a 2cm drop in the floor from one end of the room to the other, which I’ve worked out using a combination of laser and tape measures:

View attachment 293615

Based on this, I’m struggling to see how either a) their 3mm layer is going to make any meaningful inroads in levelling the floor, or b) how the DPM sandwich could work, given I understand that even though Arditex NA can work at higher thicknesses, the layers need to be quite thin when applied on top of bitumen, and again on top of their DPM?
I can't see how you can achieve much at all regards a lasting DPM in such a thin confine. The main aim of floor levelling in reality, it to have a consistently flat smooth surface on which to lay tiles, laminate, carpet, Karndean etc. It's more designed to smooth out rather than bring out of level floors back to level.
If you are concerned with damp and a sloping floor, then remove the screed, lay a physical DPM and re-screed.
 
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Yes, that would be the best option, but I understand that is much more costly. I’m really looking to do the best that can be done in a reasonable budget.
 
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JohnD

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Have you worked out where the water is coming from yet?

Black paint will not repair the defect.
 
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I suspect it is seeping up through the concrete floor - the garage to the side of the property (at a slightly lower elevation) has had wet floors throughout the recent heavy rain. The property is an early-mid 60’s bungalow (not sure of the exact year of construction) which I understand is around when DPMs started to be fitted, so I don’t know if any DPM is in place beneath the concrete.

I’m assuming there is no structural defect as it stands - certainly nothing was reported in the Level 3 survey I had carried out when I bought the place. It’s more a case of I’d like the floor levelling out anyway whilst I’m renovating the room, and it looks like the cost of adding an additional liquid DPM at the same time is minimal.
 

JohnD

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Your floor is wet, cracked and sinking. It needs digging out.
 

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