paint on dpm advice

ligertigon · 01-09-2014 9:34pm #1

looking for recommendations on brands of bitumen paint.
I will be painting this on a subfloor to create a dpm in my house as I have a damp problem.
This will then be covered with insulation and then 3 inches or so of concrete.

I cant use conventional plastic dpm as the internal walls are block and built on the slab, so I cant disturb the floor around them....

theoptimist · 01-09-2014 9:46pm

Sounds like you're looking for something a bit similar to me (I'm looking at tanking/waterproofing products for a patio) Have a look at Thoroseal and Botament. They both sound good, I'm looking for someone with actual experience of them (or other products) though. Post any info your research turns up!

ligertigon · 01-09-2014 9:50pm

will do, its so important to get this right...

theoptimist · 01-09-2014 9:57pm

yes, water is a pretty persistent thing so any system for keeping it out has to be 100% which is hard (or impossible?) to do. Add to that the fact that its going to be buried beneath screeds etc. If a problem ever develops, fixing it is not going to be fun!!

RITwing · 02-09-2014 8:54am

This is not a DIY task. Proceed only with a specialist sub contractor who should take responsiblity for radon , insulation , damp and screed finished.

ligertigon · 02-09-2014 7:13pm

This is and will be a diy task. What would a special contractor do different?

High Rouleur · 02-09-2014 9:14pm

You could try Sika TopSeal 107. You may still have an issue with rising moisture on the internal Walls though. Depending on what they are (brick, block, stone) they could be injected. This is a specialist job though

Safehands · 02-09-2014 10:56pm

ligertigon wrote: »

looking for recommendations on brands of bitumen paint.
I will be painting this on a subfloor to create a dpm in my house as I have a damp problem.
This will then be covered with insulation and then 3 inches or so of concrete.
I cant use conventional plastic dpm as the internal walls are block and built on the slab, so I cant disturb the floor around them....

This depends on the level of moisture in your floor. Have you taken any readings? Where is the damp coming from? If it is a new floor which has not dried out yet then you can go for a liquid DPM, such as Dampshield or Strongcoat DPM. They are epoxies and are very effective. However, if you are experiencing damp which is visible on an older floor then you would be advised to contact a professional damp proofing company, such as Dampco. I would avoid bitumen.

ligertigon · 02-09-2014 11:02pm

Thanks for the goodwill all.
The internal walls have a dpm, built on the subfloor which has a compromised dpm. The external walls are fine.
As the subfloor membrane is compromised AND not knitted to the walls. The bitumen paint will be used to bridge the gap between wall dpm and floor. The floor will then be raised via battens with insulation in between and then wooden floor.

My only other option is to knock all internal walls, that coincidentally support the roof, to re lay dpm.

A bitument paint would give me more confidence than the slurries mentioned as it penetrates fine cracks better and has more flexibility.

Safehands · 02-09-2014 11:12pm

ligertigon wrote: »

Thanks for the goodwill all.
The internal walls have a dpm, built on the subfloor which has a compromised dpm. The external walls are fine.
As the subfloor membrane is compromised AND not knitted to the walls. The bitumen paint will be used to bridge the gap between wall dpm and floor. The floor will then be raised via battens with insulation in between and then wooden floor.
My only other option is to knock all internal walls, that coincidentally support the roof, to re lay dpm.
A bitument paint would give me more confidence than the slurries mentioned as it penetrates fine cracks better and has more flexibility.

How old is this house?

Safehands · 03-09-2014 9:31am

ligertigon wrote: »

Thanks for the goodwill all.
The internal walls have a dpm, built on the subfloor which has a compromised dpm. The external walls are fine.
As the subfloor membrane is compromised AND not knitted to the walls. The bitumen paint will be used to bridge the gap between wall dpm and floor. The floor will then be raised via battens with insulation in between and then wooden floor.

My only other option is to knock all internal walls, that coincidentally support the roof, to re lay dpm.
A bitument paint would give me more confidence than the slurries mentioned as it penetrates fine cracks better and has more flexibility.

How do you know the floor is damp?

ligertigon · 03-09-2014 10:58am

House is built around 1975, it is on top of a hill/mound.
There is a slight damp smell in one room, and while cutting a trench in the floor for installing central heating this summer, the subfloor was damp and hasn't dried.
Also, there is efflorescence on some lower walls and plaster flaking on internal walls.
I bought the house(my first) last december, and when I lifted the laminate floor discovered a wet patch which was a central heating leak. The old central heating is now removed.

A test hole dug near the outer wall shows the floor dpm lower than the wall dpm, ( they dont meet) so there is damp bridging there for definite.

Safehands · 03-09-2014 12:04pm

ligertigon wrote: »

House is built around 1975, it is on top of a hill/mound.
There is a slight damp smell in one room, and while cutting a trench in the floor for installing central heating this summer, the subfloor was damp and hasn't dried.
Also, there is efflorescence on some lower walls and plaster flaking on internal walls.
I bought the house(my first) last december, and when I lifted the laminate floor discovered a wet patch which was a central heating leak. The old central heating is now removed. A test hole dug near the outer wall shows the floor dpm lower than the wall dpm, ( they dont meet) so there is damp bridging there for definite.

You say that the house is built on a hill. That would suggest that the water table would be quite low, relative to the house. If the heating system had been leaking for a while, that could be the source of your problem. You need to examine external down pipes and gutters for faults. The effloresence and flaking plaster suggest rising damp, but the situation of the house suggests that it probably is not. An interesting problem! I suspect that the Sikatop 107 or the not as expensive Parex Eproseal would probably solve the dampness issue, but I would like to find out where the damp is coming from first. Avoid Bitumen! It is not as good as the the others mentioned.

ligertigon · 03-09-2014 3:56pm

Thanks safehands,
it is indeed interesting trying to fault find. someone said to me that a slab sandwiched between dpm and insulation on top could take years to dry out fully after a leak!
The damp end is also quite shaded by trees so that's another factor..

High Rouleur · 03-09-2014 9:46pm

You will need to be careful how the battens are fitted as you don't want to penetrate whatever membrane you lay on the old slab. I had a similar situation with a much older propety. A very thin concrete slab (70mm) had been installed at one point. When I lifted vinyl carpet etc. the floor was saturated. I first applied the Sikatop product with a mortar brush. It is quite workable and doesn't need to be trowel applied and will go in to cracks. When this had cured, I bonded treated battens to the floor at 600mm centres using grip fill/tec 7. After this I painted over the whole lot with a bitumen primer and laid sheets of bituthene 8000 over. This served the dual purpose of providing a very heavy water proof membrane and also held the battens firmly in place as it lapped over them. You could lap the bituthene with the existing dpm under the internal Walls. I then fitted a timber floor which was nailed to the top of the batten. This was an alternative to removing the old floor slab and casting new.
The area involved was quite small due to the size of the house. That was over 10 years ago and there has been no issue with damp since

Safehands · 03-09-2014 10:44pm

High Rouleur wrote: »

You will need to be careful how the battens are fitted as you don't want to penetrate whatever membrane you lay on the old slab. I had a similar situation with a much older propety. A very thin concrete slab (70mm) had been installed at one point. When I lifted vinyl carpet etc. the floor was saturated. I first applied the Sikatop product with a mortar brush. It is quite workable and doesn't need to be trowel applied and will go in to cracks. When this had cured, I bonded treated battens to the floor at 600mm centres using grip fill/tec 7. After this I painted over the whole lot with a bitumen primer and laid sheets of bituthene 8000 over. This served the dual purpose of providing a very heavy water proof membrane and also held the battens firmly in place as it lapped over them. You could lap the bituthene with the existing dpm under the internal Walls. I then fitted a timber floor which was nailed to the top of the batten. This was an alternative to removing the old floor slab and casting new.
The area involved was quite small due to the size of the house. That was over 10 years ago and there has been no issue with damp since

Not surprised at that. Talk about belt and braces! Fair play to you. I'm not sure that detail would be a whole lot cheaper than a polymer modified waterproof screed though. But you will never need to worry about moisture. Did you ever find out why the floor was so wet?

ligertigon · 04-09-2014 12:08am

High Rouleur wrote: »

You will need to be careful how the battens are fitted as you don't want to penetrate whatever membrane you lay on the old slab. I had a similar situation with a much older propety. A very thin concrete slab (70mm) had been installed at one point. When I lifted vinyl carpet etc. the floor was saturated. I first applied the Sikatop product with a mortar brush. It is quite workable and doesn't need to be trowel applied and will go in to cracks. When this had cured, I bonded treated battens to the floor at 600mm centres using grip fill/tec 7. After this I painted over the whole lot with a bitumen primer and laid sheets of bituthene 8000 over. This served the dual purpose of providing a very heavy water proof membrane and also held the battens firmly in place as it lapped over them. You could lap the bituthene with the existing dpm under the internal Walls. I then fitted a timber floor which was nailed to the top of the batten. This was an alternative to removing the old floor slab and casting new.
The area involved was quite small due to the size of the house. That was over 10 years ago and there has been no issue with damp since

Thanks for that, its pretty much what I am about to do. though I have hit a snag...
the subfloor is high and low all over the place by at least 2 inches, this means the batons will need to be shimmed all over the place, and thats just one room:(
Also the subfloor is about 10mm higher than the blockwork dpc so I will have to dress the wall section so that its lower...

paint on dpm advice

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