Basement Tanking or Sump Pump

nam

nam

nam

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Hi All,
Anyone here have any experience of basements. I have a basement not dug out which was recently flooded there is currently no tanking or sump pump installed

what is most cost effective to prevent the flooding a sump pump or Tanking
 
No experience of cellars, but just from what i recall researching/reading when we almost bought a house with a cellar. I recall tanking the cellar put a waterproof layer around the walls to prevent flooding, whereas a sump pump would just automatically kick in when the cellar starts to flood. The former being significantly more expensive.

The ultimate question is what your intended use of the cellar is - if you want to have it as a liveable room (say a home cinema) then it would need tanking. If it's just for storage just as you would with a garage, then you'd probably get away with a sump pump, although i wouldn't put anything valuable/expensive on the floor.
 
Let me guess, East London? I have 2 colleagues who spent the weekend bailing out their vehicles (parked in underground car parks).
 
Search for the ICE Clients' Guide: Reducing the Risk of Leaking Substructure.

BS8102 is the code for waterproofing stuctures in the ground and it recommends (for anything non-trivial) 2 independent forms of waterproofing for habitable basements and the like.

Water always wins so SFAIK the best route is to always aim to make one of those a drained cavity solution with a pump to deal with the water that does get in. You lose space by installing the cavity drain, but it can be plastic egg crate faced with moisture resistant plasterboard fixed back to the existing walls if they are good enough.

For an existing structure your other method would be some form of tanking, probably behind (ie outside of) the cavity drain, but it will obviously depend on the specifics of your building and requirements etc.

Any system will need to be designed for the head of water pressure it is being asked to resist - in this case of flooding that is above ground level! It only works if the water can't over-top the basement and come in from above, eg down the internal stairs. If that is the aim you also need to consider the flood resilience of the ground floor too, and how the water is kept out of, and ideally away from, the property itself to begin with.

Find an independend consultant to design you a system, do not go to a supplier who has a vested interest in selling you products (often with heavily caveated warranties like "we only cover the goods themselves, not consequential damages or losses" - i.e we only pay to fix the membrane, not the finishes removed in getting to it, or the contents that were damaged when it sprung a leak). Probably either a waterproofing consultant or a suitably qualified architect.
 
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A sump pump system involves some kind of tanking but this directs the water to the lowest point, the sump, which is them pumped out.

As mentioned, just tanking is trying to make it all completely waterproof, but has a high failure rate, water always wins
 
dLockers said:
Let me guess, East London? I have 2 colleagues who spent the weekend bailing out their vehicles (parked in underground car parks).
Click to expand...

Correct 4-5 inches came in from the rear of the property where the current drainage was not adequate. I had 2 drain snake flood bags which could not cope water was coming through the walls in the corners.

I hired for 7 days from HSS industrial dehumidifer and 2 dryers and has made a massive difference already though i am aware there is a another storm expected on Thursday.

As the basement is only for Storage with a bare concrete floor i need to solve 2 issues

1) Prevent the water getting in from outside which i believe is due to the small Sump drain outiside not being adequate
2) Improve the current musty damp smell


The photo shows the low-level drainage which could not cope. This is what i am hoping can be dug-out for a pump and cavity drain. Any ideas on expected costs ?

Drainage.jpg
 
First thing, it might be worth getting your drainage runs CCTV surveyed. You may have a duff/collapsed outlet pipe. Or if not, the problem may be 1) too small a pipe out in which case you need to replace/attenuate at your end, or 2) backing up from the mains if it's overcapacity. The latter can be mitigated by a non-return valve (or by Thames Water cleaning their sewers if they're blocked with fatbergs). The former can utilise something like a waterbut or similar tank to hold surplus water in a storm event then let it discharge at a rate the drain / mains sewer can handle.
 
Thank you all for your advice i got a specialist in who i explained the issue to they recommended a low level puddle pump which would require no digging. There quote seems to be too expensive for me (Labour) for half a day if that of work

Basementpumps-quote.jpg
:eek:


i would like to buy a low level puddle pump myself and get a tradesman to fit or attempt myself if i can work out which UPVC pipe and non return value i need


This a diagram of what i would like to get done

1.jpg



Any advice here ?
 
For plastic drainage a reliable brand is Hepworth. You could try contacting them directly and see if they can help, they might say no but you've nothing to lose by asking.
 
nam said:
There quote seems to be too expensive for me (Labour) for half a day if that of work
Click to expand...

450 day rate for a groundworks engineer in London sounds about right - we paid 45/hr for chap who did our drainage for our extension and your hourly rate is only slightly more expensive than that.
 
amigafan2003 said:
450 day rate for a groundworks engineer in London sounds about right - we paid 45/hr for chap who did our drainage for our extension and your hourly rate is only slightly more expensive than that.
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Only slightly more?

With VAT added on it comes to 540. And assuming half a day is 4 hours, gives an hourly rate of 135/hr which is three times 45/hr.
 
I have worked with many basement waterproofing systems over the years. The key point to know is that tanking and sump pumps are not the same. They are made for different problems.

Many people think tanking (Type A) is the easy solution. However, what is often overlooked is that tanking depends on good substrate preparation and strong long-term bonds. If the background is damp, dirty, or moving, the pressure will find a weak spot. Once that happens, water pressure just pushes its way behind the coating, and you’re back to square one.

This is why, especially in existing basements, tanking tends to fail more often than people expect. You don’t get a second chance with it. If it de-bonds, it’s game over.

The alternative is a Type C cavity drain system. This doesn’t try to hold back the water, it accepts that water will always find a route in and manages it instead. This is all about hydrostatic pressure. You line the walls/floor with a studded membrane, create a controlled drainage path, and discharge everything to a sump/pump system. It’s much more forgiving because it depressurises the water rather than fighting it.

BS 8102:2022 (the British Standard for basements) actually classifies Type C as the safest option for most refurbishment situations because you’re not betting everything on a single bonded coating.

In retrofit basements with any history of dampness, a pump system is typically the more reliable long-term option. You can still combine tanking with a cavity drain (many waterproofing designers do this for redundancy), but going “pump only” with a well-designed drainage layout is very common now.

If you want a more detailed breakdown of the difference between tanking and drained systems, these two guides explain it pretty well without being salesy:
And for the pump side, this explains how a sump setup integrates into a cavity drain system:
Worth a read if you’re mid-decision. Newton has been around for a long, long time and is well recognised in the industry. The key is to avoid relying solely on tanking in an old structure. The risk of future pressure build-up is greater than many people realise. Happy to answer anything else if you’re weighing up options.
 
mrsegghat said:
I have worked with many basement waterproofing systems over the years. The key point to know is that tanking and sump pumps are not the same. They are made for different problems.

Many people think tanking (Type A) is the easy solution. However, what is often overlooked is that tanking depends on good substrate preparation and strong long-term bonds. If the background is damp, dirty, or moving, the pressure will find a weak spot. Once that happens, water pressure just pushes its way behind the coating, and you’re back to square one.

This is why, especially in existing basements, tanking tends to fail more often than people expect. You don’t get a second chance with it. If it de-bonds, it’s game over.

The alternative is a Type C cavity drain system. This doesn’t try to hold back the water, it accepts that water will always find a route in and manages it instead. This is all about hydrostatic pressure. You line the walls/floor with a studded membrane, create a controlled drainage path, and discharge everything to a sump/pump system. It’s much more forgiving because it depressurises the water rather than fighting it.

BS 8102:2022 (the British Standard for basements) actually classifies Type C as the safest option for most refurbishment situations because you’re not betting everything on a single bonded coating.

In retrofit basements with any history of dampness, a pump system is typically the more reliable long-term option. You can still combine tanking with a cavity drain (many waterproofing designers do this for redundancy), but going “pump only” with a well-designed drainage layout is very common now.

If you want a more detailed breakdown of the difference between tanking and drained systems, these two guides explain it pretty well without being salesy:
And for the pump side, this explains how a sump setup integrates into a cavity drain system:
Worth a read if you’re mid-decision. Newton has been around for a long, long time and is well recognised in the industry. The key is to avoid relying solely on tanking in an old structure. The risk of future pressure build-up is greater than many people realise. Happy to answer anything else if you’re weighing up options.
Click to expand...
You'd hope after 4 years it would be sorted,
 
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