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Bitpipe

Basement Waterproofing

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I'm re-creating a few threads from e-build where I shared experience of building my 'passive' basement, useful starting points for follow on discussions

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The original poster was enquiring about waterproofing basements and dealing with the conflicting advice from architect and contractors. My reply: 

Unless you're 'in the water', which your ground investigation will reveal, warrantied waterproof concrete on its own should be sufficient.

We're on undulating layers of clay, lynch hill gravel and seaford chalk so relatively free draining and don't hit water until 6m. Basement excavation was 3.5m so we went for 300mm waterproofed concrete with a land drain around the slab base to a 5m deep soakaway and a 1m wide clean stone backfill.

We used an approved Sika contractor and had regular inspections from Sika during the pour, checking water bar placement, penetrations etc. We now have their 15 year insurance backed warranty against water ingress.

The overall 10 year build warranty (from Ark) was satisfied by this as were BC.

We have friends nearby who built close by the Thames and their basement is half submerged in ground water - they used Glatthar and were very satisfied but it wasn't cheap.

We did our entire 122m2 basement for £120k with a single contractor which included demo & cart-away of existing building, excavation & muckaway and the construction of the basement itself - plus all services (fouls, rainwater, water, gas & BT duct & electric). I sourced the under slab & wall insulation separately as they weren't familiar with it at the time.

Glatthar wanted about £100k for just the basement construction and we would have had to fund the groundworks separately - which would have been at least half as much again.

We also designed our basement as an 'open box' with no structural internal walls so we are free to change the layout if we wish, currently having it framed out which is only costing a few £100 in labour and timber.

Good luck, lots FUD surrounding basements and many of the contractors push their preferred systems (typically with additional cost) in a take it or leave it fashion but get what works best for your site and gives you the necessary peace of mind and suits your pocket. 

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As you know I did not use any waterproofing in my basement, relying on no groundwater (if you have this it is destined to leak at some future point) and higher partial vapour pressure of moisture in the air inside than outside it, this is always the case.

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Tony, can you explain more on exactly what you done for waterproofing your basement.  Cheers 

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