How a sump and pump keeps a basement conversion dry (Type C waterproofing)

A Type C cavity drain membrane waterproofing system cannot hope to work without some means of taking water away.  If water builds up a head against the membrane – IT WILL FAIL.

Gravity drainage works well, where it can be used, but for many occasions a sump is needed, with one or more pumps to carry any water out of the basement, to waste.

I visited a basement conversion site in Leeds the other day – where Brick-Tie Preservation had just installed a Safeguard Sentry 2 system for a client.  This is a proprietary automated sump-pump system with two high capacity pumps and a failsafe alarm too.  The unit is hidden in the floor of the basement, ready to pump automatically when needed.

The Sentry 2 has a volume of about 150 litres, which can be filled with up to three pumps, should that kind of flow rate be needed.  I don’t often use a single pump; two being my preferred minimum.  After all, an investment in a basement conversion runs to at least several thousand pounds, even without the kitchen,gym, or whatever is going in afterward, so a few quid for the extra pump is money well spent, just for the peace of mind it gives.

Anyway, for those who haven’t see a sump in action this short video was shot just to demonstrate how fast the pumps can get rid of water.  I filled the sump with a hosepipe and switched the power back on. Don’t worry too much about the noise – that was vibration due to my screwdriver falling in and getting trapped under one of the pumps – it was quiet as a mouse once I realised and fished it out.

Sentry2 sump demo

I come across quite a few basements in and around Leeds, which have membranes with dry linings, but no drainage – sump or otherwise.  These are all gambles and when they go wrong; which is often, it means a complete strip out.  I’ve recently completed a basement repair in Horsforth where a flood happened because of the omission of a sump.

No drainage under the membrane – no guarantee.

Dry Rot

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Copyright © 2010 Preservation Expert. Legal Stuff: All the advice and information in the posts on my blog is made in good faith and is based on my experience and knowledge at the time of writing. However, nobody is infallible and whilst I’m confident that most of what I write about preservation issues is accurate, there’s a good chance there’ll be an error or two somewhere. I do change my mind about stuff, as I gain more experience. In view of this you must make your own decisions on whether to follow any advice I write and think about this; I could be wrong. No responsibility will be accepted by the author for any losses anyone may suffer as a result of any mistake or for the consequence of any action you take as a result of reading this blog. If you do suffer a loss, resulting from anything I’ve written, a verbal heartfelt apology will be your only compensation.