How best to approach an underground chamber.

[Jon-uk]

I need to dig out a chamber for pond filter equipment approx 1 metre deep, 3 metres across and 2 metres wide. How should I best finish the job. My very limited (read non existent) building knowledge says that I can line and floor with breeze blocks and simple add one layer of breeze blocks to the walls, using mortar for both and job done.

But then I think about water collection and should I install a sump collection, do I need a damp membrane between the blocks and the soil walls/floor blocks and soil etc etc.

It will be covered with a loose cover.

Any advice gratefully received!

 

[Newboy]

You need a foundation for your walls - easiest might be a suitably sized slab covering the floor & wall area then build your walls off the slab. If it's going to open to the elements then little point in trying to waterproof (tank) the walls - a sump with some means of extracting and water would be simpler.

Don't underestimate the risk of walls collapsing due to the weight of the surrounding ground and any water build up behind them - you are building 4 retaining walls which need a bit of design to ensure that they are safe.

 

[Jon-uk]

Useful reply, thank you. If I employ general labourers would it be reasonable to expect them to know how to do this properly?

 

[Mottie]

Absolutely not! They're labourers and you will be expected to tell them exactly what you want done. For this job, why not employ a skilled brickie?

 

[Jon-uk]

Appreciate your advice.

 

[HERTS P&D]

Why don't you have a 'pumped' pond and not gravity feed? That way your filter can be on ground level.

Andy .

 

[Jon-uk]

Main reason is to allow a four inch drain to server a bottom drain, which will gravity feed a filter unit. Pumped solutions tend to liquidise sediment etc making filtration more difficult and leading to cloudier water. A four inch pipe and a bottom drain with a seive can cope with solids that would foul a pumps impeller.

 

[HERTS P&D]

If your pond is raised, with 3ft in the ground and 3ft out of the ground then you can have a gravity filter.

This will mean digging down approx. 4ft to allow for bottom drain and base.

Andy