Flags in cellar - Floor in a cellar

[Bern]

A bit of an odd one perhaps. I am to lay a new floor in my cellar, size about 12 foot x 15 foot. The problem is the water table seems to be about 2 inch below the old floor level in dry weather. In wet weather the level rose and the cellar collected water.

I have dug out the old concrete floor which was one inch concrete laid on one inch of ash. In addition I built a sump with a float switch activated pump. This removes flooding after rain, but on the dug area water still collects and remains. After a break of three months, to watch and see, the puddle formed is still there. The ground is yellow clay, a bit harder than cold putty, with clay type shale in some small areas. Filling the builders skip full was...well, let's say I was glad when was done.

My thought is to lay a base of 20 mm gravel to a depth of a couple of inches followed by an inch or so of pea gravel. On top of this to lay two foot square concrete flags. My intention is to have a flexible floor stood on ( water permeable ) gravel.

Compacting may prove difficult due to being inside and the danger from petrol engine fumes. I think I have to accept settlement will take place so the flags to be laid with a three eighths inch gap grouted by a 7-1 sand / cement mix. The intention being it should be easy to run a disk down through the grout to enable flag lifting, repacking and subsequent re-laying.

Do you have any helpful comments?

[84-1093879891]

So what's on the floor now? Just bare clay?

The idea to use a clean gravel laying course is fine, but how will you protect your sump?

And rather than 600x600mm flags, I'd consider using the small element flags, such as the 300x300mm units or the 400x400mm ones. These would be easier to lift, if necessary, and are easier to lay. The joints could be filled with a polymeric sand, such as GeoFix, which would be ok as it hardens enough to maintain joint width without bonding to the edges of the flags and making them hard to remove, if/when necessary.

As for compaction, there are lecky compacting yokes available, if you ask at your local hire shop. They're not brilliant, and I wouldn't recommend their use for a driveway project, but they'd be ideal for a cellar.

[Bern]

The cellar floor was concrete, but now is bare and wet clay. The sump is, in effect, a brick box below ground level. Concrete base, single course class B's, about 18 inch deep. A bit like a brick manhole, but as I say, only one brick thick instead of two. In the lower portions the vertical joints between bricks are half inch wide and do not have mortar. On the outside of the 'box' is 20 mm gravel to permit water passage down from clay floor level.

Pump protection seems unnecessary as the water seems to be always clear. I am aware of the problems abrasive silt could cause, but so far this looks like not an issue.

You recommend polymeric sand, such as GeoFix. This I am not familiar with this, but I'll have a word with my BM, who will doubtless give me the straight-fase stare, but will then explain.

Amazing site, must be quite time consuming. Thanks for the advice.