Basement Water Penetration

Hi All,

I am a total newbie, so I am not sure whether this question has been answered in another thread. But I shall ask anyway and I hope that there is some advice.

I have a new basement built that has concrete reinforced walls on the 2 sides facing the neighbours. The wall under the house foundations is also reinforced. The builder has used delta membrance against the walls.

However, there is a leak that has penetrated one of the walls from the neighbour. This neighbours property is elevated as we are on a slope and the ground material is clay.

My question, is there anything that can be done to prevent the water from leaking through? The builder seems to say "no", that the water will seep through somehow. He is channelled it out through the floor of the basement.

I really hope that someone can help, as I don't want to regret not doing something now, before it becomes a major headache.

Cheers, KSG.

Provided that products suitable for the job have been used, if its leaking he's not installed it correctly. Waterproofing basements utilising membrane systems are very unforgiving if the installation is not 100% perfect and I mean 100%.

Thanks very much for the info and the quick response.

I am not sure that he has used anything else apart from the reinfoced concrete wall. I don't believe that there was any DPC against the walls or any other type of material.

The walls have been rendered and then a delta membrane added dor the water to find a route to the channels. Then he is going to insulate with 10mm insulation and finally plasterboard.

From your rsponse, you seem to imply that there should have been some other products used. But I am not awrae of any. Would appreciate your help.

Thanks, KSG.

Ok so I presume the system he's used is the light grey coloured knobbly nylon type rather than a black bitumous type of membrane? The knobs are facing the wall I presume? In that case they are a bit more forgiving when being installed. Although I'm not really familiar with that particular manufacturer I have specified similar ones, the system works by allowing any water that penetrates the wall to trickle down the face of the wall into a preformed Delta plastic gulley at the junction where the floor meets the wall. This is then pumped out or drain out naturally. On the floor should be a similar membrane that laps up the wall in front of the wall membrane. Where the 2 join the joint should be sealed with a Delta jointing product. Vertical joints between the sheets on the wall should also be sealed. The membrane should be fixed to the wall at centres specified by the manufacturer normally with their own special fixings which have a special seal on them. The floor membrane also needs to be sealed at the joints although does not need fixing down as the screed etc will do that. Why did he render the wall first and where is it leaking through exactly? through a joint? through a fixing?
Is there any writing on the membrane that tells us exactly what he's used, what do the fixings look like, how has he sealed the joins can you post some pictures.

DIYnotsure said:

Then he is going to insulate with 10mm insulation and finally plasterboard.

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Thats not good! Are you sure?

would it be an idea to paint a bitumin paint on it before you go any further or stick a damp proof membrane on it before you cover it all up.
a good website to help you look things up is
www.bluebaybp.co.uk

jeepman said:

would it be an idea to paint a bitumin paint on it before you go any further or stick a damp proof membrane on it before you cover it all up.
a good website to help you look things up is
www.bluebaybp.co.uk

Click to expand...

Thats hardly fixing the problem though is it? Do you understand how the system he's used is supposed to work? How would you stick insulation and plasterboard to a dpm withought penetrating it?

Hi, Thanks for thge responses, much appreciated and insigthful.

Here are some photos. Letters A and B shows where water has seaped behind the membrane down to the ground. At point A in the ground, a little digging showed quite a bit of water in the ground.

Letter C shows exactly the point behind the membrane where water is coming out through a hole, it is approximately the size of a 50p piece. On Friday, when it was raining (not heavily) there was quite a large pool of water. The channels are still covered and it had risen by about 4 inches. The water was pumped away by a portable pump.

As mentioned is there a way to stop the water coming through ? If so, would that just push the problem elsewhere ? What is the best approach at this point? As you can see the walls and floors have yet to be insulated (celotex) and covered.

Thanks again, KSG

Have you read my last post? The whole point of this system is that it allows water in through the wall where it drips down the face of the wall behind the membrane and is then drained or pumped away. Water is bound to show up on the floor either from dripping down the wall or seeping up through the basement floor.

Here are my observations:
It looks like he’s been a bit frugal with the fixings.
Presumably the battens are screwed to the wall penetrating the membrane. This could be very bad if he's not used the manufacturers fixings. What fixings have been used?
Why does the membrane not go down to the floor?
There isn’t a membrane on the floor. Does he have any plans to fit a membrane to the floor?
There isn’t a preformed gulley like I mentioned before. Is he going to fit a gulley around the perimeter? I cant see how he is going to be able to join a floor membrane to the wall one if the battens are already installed.
Pleas re-read my posts and answer my questions:
The membrane has the knobbly side facing the wall I presume?
Has he sealed the joins in the sheets?
By how much does one sheet overlap the other where they join?
Why did he render the wall first?
10mm insulation is nowhere near enough.

It looks like a bit of a bodge so far to be honest, whilst the system chosen is correct the installation is lacking much good workmanship if he’s finished waterproofing which I presume he has hence he’s about to insulate the walls!

This is a PDF from the manufacturer. You will see the installation should be quite neat with the drain round the edge and the membrane on the floor. http://www.deltamembranes.com/pdf/DELTA SYSTEM 500 6 page.pdf

I’m not being rude but if you don’t answer the questions little progress can be made here.

PS the second photo shows a (presumably) external wall that's been closed with blockworked turned into the brickwork, this terrible. It should be closed with a proprietry insulated cavity closer. Alarm bells should be ringing!

These are answers to your questions:
- The delta membrane does have the knobbly side facing the wall.
- He has not sealed the joins in the sheet yet.
- Not sure of how much the sheets overlap.
- Not sure why he haas rendered the concrete reinforced wall.
- I am told that the 10mm celotex insulation should be enough. From what you say this does not appear to the case.
- He has used the manufacturers black sticky fixings into the membrane and then the batons into the fixings with screws.
- He has yet to complete the floor. The floor channelling/gulley has been created and he just needs to remove the floor covering that he has in place (this is currently wooden timbers in the concrete reinforced floor) and then add the membrane to the floor. I am now assuming that he would then create the floor at a higher level than the floor membrane. This is where I need to find out some more details.
- I am assuming that the floor membrane will rise up behind the wall membrane (?).

Ok Alarm bells were ringing they just seem to be ringing louder now.

Ok this has what has been done. The retained walls (which are used as a foundation for the extension walls above, this was the original idea) are reinforced concrete steel walls, the concrete is a specific mix that is supposed to be waterproof. It has been rendered and then the delta membrane applied.

My questions are:
1. What should have been done next ?
2. Is leaking or water seepage a problem, is it normal and acceptable ?
3. What should have been done to prevent it ?
4. What can be done now ?

I understand the reason for the membrane system, how to deal with the problem. What my issues are should this be happening at all (has the builder missed something) ? Is the builder correctly building the basement ?

Appreciate all your help Freddymercurystwin.

First of all, have you had drawings prepared for any the works, have you got Planning Permission, are you trying to get Building Regulations Approval?

In response to your post my comments are in blue.

- The delta membrane does have the knobbly side facing the wall.
That’s one good thing then lol!
- He has not sealed the joins in the sheet yet.
He should have done that before he stuck any battens to the wall
- Not sure of how much the sheets overlap.
If they’re not sealed yet you should be able to check?
- Not sure why he haas rendered the concrete reinforced wall.
Because he’s an idiot?
- I am told that the 10mm celotex insulation should be enough. From what you say this does not appear to the case.
He should be using somewhere around 60mm insulation on the face of the battens not between them the actual thickness needs to sought from the manufacturer though as they’ll need to work it out.
- He has used the manufacturers black sticky fixings into the membrane and then the batons into the fixings with screws.
Are you saying he’s just screwed the battens to the walls and they’re just normal screws that penetrate the membrane? If so this is wrong.
- He has yet to complete the floor. The floor channelling/gulley has been created and he just needs to remove the floor covering that he has in place (this is currently wooden timbers in the concrete reinforced floor) and then add the membrane to the floor. I am now assuming that he would then create the floor at a higher level than the floor membrane. This is where I need to find out some more details.
As mentioned a gulley needs to be installed and a membrane applied to the floor and lapped up in front of the wall membrane.
- I am assuming that the floor membrane will rise up behind the wall membrane (?).
The floor membrane should rise up and should be in front of the wall membrane not behind this is fundamental to the systems success. It should be sealed.
Ok Alarm bells were ringing they just seem to be ringing louder now.

Ok this has what has been done. The retained walls (which are used as a foundation for the extension walls above, this was the original idea) are reinforced concrete steel walls, the concrete is a specific mix that is supposed to be waterproof. It has been rendered and then the delta membrane applied.
Are you saying the new basement walls are reinforced concrete or originally were but are not now? Opinions seem divided as to whether concrete can be made waterproof or not, waterproof concrete is the same as any other concrete but with a lot more reinforcement. In any case It’s a bit of a moot point though as if you only rely on the concrete and then it does fail, its extremely expensive to then waterproof something in retrospect so you always just use membranes or similar to start with (or should lol).

My questions are:
1. What should have been done next
See below
2. Is leaking or water seepage a problem, is it normal and acceptable ?
As mentioned in my last post: Water is bound to show up on the floor either from dripping down the wall or seeping up through the basement floor.
3. What should have been done to prevent it?
Prevent what exactly? Its supposed to drip down the wall behind the membrane. See answer above.
4. What can be done now ?
See below
I understand the reason for the membrane system, how to deal with the problem. What my issues are should this be happening at all (has the builder missed something) ? Is the builder correctly building the basement ?

No, he ought to:

Ensure the overlap is what the manufacturer requires.
Ensure the overlaps are sealed properly with the correct sealant.
Install a floor gulley and means of draining or pumping out the water.
Install a floor membrane and seal it against (in front of) the wall membrane with the required overlap and ensure any overlaps are sealed properly with the correct sealant.
Make sure any penetrations through the membrane are done so using the manufacturers methods/own fixings.
Fix enough insulation to ensure the walls achieve the U value stipulated by Building Control.

Edit: this is roughly what the detail should look like at the floor/wall, this is from a job I did about 4 years ago with a different manufacturer but the principal is the same.

There are a number of features of the installation that appear to be lacking. However, the glaring fault is that there is no membrane on the floor, no perimeter drainage, and no sump system. Sometimes cavity drainage membranes are used in this way (applied to walls only) in above-ground situations. However, in a basement situation it really should be applied to walls and floor.

Yes their are drawings and we do have all the relevant permissions. The next part will be building regs approval.

The application of the membrane is yet to be finished. The builder has yet to add the membrane to the floor and as mentioned there are channels in the concrete flooring that have to be uncovered. These lead out under the doorway (1st picture). Then there is some space in front of the basement for a pump. So it appears that he is doing this correctly, even though there are some issues, rendering, overlapping and seals.

Points mentioned:
1. Water is bound to show up. I didn't think that it would appear through new walls and concrete floor so rapidly.

2. The 60mm insulation, you mention that it should go on the face of the batons rather than in between. Also the 10mm celotex one would not be good enough thermally?

3. The seals will be made. The screws are not penetrating the membrane.

My issue is the fact that a wall that is a new and has reinforced water resistant/proofing concrete erected 6 months ago has been leaking water so quickly. The point is shouldn't the wall have held out the water better, ensuring that it did not seep through the wall. This is the problem I am trying to understand.

The delta membrane will be used, but is there anything else to waterproof or apply to the wall or alternatively redirect the water away ?

Is it recommendable to seek the advice of another basement professional service or specialist ? This builder has built basements before but I feel seeking the advice from another party may save me from major headaches later (provided I get sound advice !!)

Thanks, I really appreciate the information and questions asked.
KSG

Hello KSG, wer're getting somewhere now,

Yes their are drawings and we do have all the relevant permissions. The next part will be building regs approval.
They should have made at least one inspection to look at the foundations for the basement walls, why are they not involved yet?

The application of the membrane is yet to be finished. The builder has yet to add the membrane to the floor and as mentioned there are channels in the concrete flooring that have to be uncovered. These lead out under the doorway (1st picture). Then there is some space in front of the basement for a pump. So it appears that he is doing this correctly, even though there are some issues, rendering, overlapping and seals.
If he's going to do everything I said needed to be done in my last post there shouldn't be any problems.

Points mentioned:
1. Water is bound to show up. I didn't think that it would appear through new walls and concrete floor so rapidly.
See answer later on.

2. The 60mm insulation, you mention that it should go on the face of the batons rather than in between. Also the 10mm celotex one would not be good enough thermally?
Correct. You could stick it between the battens but you would need more overall as the battens would be a good route through the wall for the heat to escape via. Whats known as a 'cold bridge'. So it generally makes sense to have slightly thinner insulation on the face of the battens. To be honest when Ive done this before I've just applied inusulated plasterboard on dabs straight onto the membrane without the need for the battens which is what my detail shows. You need to achieve a U value of at least 0.30W/m2K. There is no way 10mm Celotex will achieve this as mentioned I guessed at about 60mm the manufacturer will need to work it out exactly. I normally specify Kingspan rather than Celotex as their technical assistance is vastly superior and more often than not its cheaper. (Celotex and Kingspan are very similar products btw)

3. The seals will be made. The screws are not penetrating the membrane.
Good

My issue is the fact that a wall that is a new and has reinforced water resistant/proofing concrete erected 6 months ago has been leaking water so quickly. The point is shouldn't the wall have held out the water better, ensuring that it did not seep through the wall. This is the problem I am trying to understand.
Sorry but I would be amazed if what was specified was actually close to 'waterproof' (grade C35 I think) concrete. I thought you meant the walls were newish, 6 months is plenty of time to allow water to seep through. Its nothing to be worried about. This is why I mentioned in my last post that you must use a membrane of some kind to keep water out of a basement and not just rely on the concrete (hence you are!). Water is a buildings worst enemy, if it can, it will find a way through! That's why its easier to go into space than travel to the deepest depths of deepest oceans

The delta membrane will be used, but is there anything else to waterproof or apply to the wall or alternatively redirect the water away ? The ethos behind this system is that water IS allowed to seep through the wall, but then it is kept behind the membrane, drips down the wall and is drained away in the gulley on the floor. Again, if he's going to do everything I said needed to be done in my last post there shouldn't be any problems.

Is it recommendable to seek the advice of another basement professional service or specialist ? This builder has built basements before but I feel seeking the advice from another party may save me from major headaches later (provided I get sound advice !!)
You could try and get the area rep from Delta Membranes along for a visit to point out the error of the builders ways, you're builder may not be too impressed though! If you're really worried you could apoint someone to oversea this aspect of the work though you need to pay them for a considered opinion and expect them to charge you for researching the system, as you say another builder or 'basement expert' is likeley to be reluctant to get involved and may be biased. I too have experience of trying to get unbiased opinions, it is extremely hard.

It really comes down to how much trust you have in your builder and making sure he does everything he's supposed to. You can study the technical documents on the Delta Membrane website and speak to their technical department, they will likely send you drawings of all of the junctions if you ask. You are in charge and YOU need to understand the system, how it works and how its is supposed to be applied so that you can spot what he is doing wrong.

When all's said and done at the end of the job:

freddymercurystwin said:

Provided that products suitable for the job have been used, if its leaking he's not installed it correctly.

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Goodluck!

When these types of cavity drain systems are used over new concrete it is important to try and minimise seepage of water through the concrete. This is because the water will carry dissolved free lime from the concrete which can clog up the sump pumps.