Damp Proofing Question

Do i need to have a sump pump installed in my cellar if i am having it water-proofed?

cellar has black rot due to poor ventilation and is under ground level, but has never flooded before. I have had several damp-proof companies come to have a look, and some say it must have sump pump due to BS regulations or something, and others say, no the floor is dry so doesnt need one, just needs p20 membrane tanking system and humidistat fan.Please advise me, it's alot of money to gamble and I dont know who to believe.
thanks a million

6 Answers

Best Answer

Dear Kali,
The key to the answer of your question is where you said the room is below ground, to meet the requirements of the manufacturers of the membrane system and British Standards fully, you would need to install a sump pump system. The system you mention (Cavity Drain Membrain) cannot deal with standing water and if not drained by a pump or gravity drainage system will fail catastrophically in the event of water build up. Even though the property has not flooded before a slow build up of ground/rainwater would still be possible.
So the correct answer is yes - in the absense of any reliable drainage you will need a sump pump in that situation.
Mike Davison cssw (certificated Surveyor in Structural Waterproofing)

Answered 19th Mar 2011

Dryspace Maintain Ltd

Member since 7 Nov 2010

all the p20 tanking system does is direct the moisture/water that is in the cellar walls,down the outside of the membrane usually channelling it into a sump and pump system in the floor, which ejects the water into the mains once it reaches a pre set level, if you want to keep the cellar dry this is the system you need to use really, sounds like you need some air down there first , before you go ahead with work have a few sub floor airflow vents fitted to make sure its not just a ventilation problem,

Answered 3rd Mar 2011

jc plastering

Member since 13 Nov 2010

No feedback

without seeing your cellar it sounds to me you need fresh air down there .there are a few ways to do this ,the cheapest is to put vent pipes in every 2 metter and give it a chance to start working if you have the walls tanked you would just be throwing good money away untill you sort the ventilation problem out

Answered 3rd Mar 2011


Member since 11 Jun 2008

if you are waterproofing the cellar by membrane yes you need a pump.
ventilation ??? continuous operation extract ventilation ray

Answered 31st Oct 2012

lb waterproofing

Member since 1 Apr 2010

Hi im Derek from refresh Carpentry and Building Ltd I recently have completed a similar Cellar referb in Portsmouth. I wouldnt think a sump pump was necessary. i fitted a snorkel vent and added a radiator plus fitting a DPM and tanking the walls this has fixed the problem for my customer its now warm and dry in the cellar hope this helps.

Answered 3rd Mar 2011

Refresh Carpentry And Building Ltd

Member since 24 Oct 2008

No feedback

needs doing to b.s.8102 get it done right by a pca member not a builder good luck

Answered 4th Mar 2015

JM Damp and Timber Treatment

Member since 4 Feb 2015

Need help with your project?

We have tradesmen ready to help you. Post a job, read reviews and hire today.

Post a job

Need some help?

Post a job on MyBuilder to find quality, local Damp Proofing Specialists who can help you with your project.

Search all questions