Foundations / void under block and beam floor keep flooding

[OneDove]

Hi all, I am new to this forum - thank you in advance for all your help.

We moved into a property which had previously had a large-ish extension to it. The lounge was extended with a bedroom above and at the same time a conservatory was added to the back. The site slopes away from the house and as a result the conservatory base (and I presume the lounge extension) have been built using a block and beam floor. Also the conservatory base has an access hatch left in the rear base wall to allow storage under the conservatory (as you can see in the picture) you need to step down around 18 inches into the storage area which is just a clay soil. Since I have lived in the property I have noticed that the void left under the conservatory fills with water after rainfall creating a paddling pool of 18 inches in depth. I am unclear whether this is due to rain water or surface water entering the hatch, or water coming up through the clay soil under the conservatory.

I have been pumping water out of the conservatory base to make sure that it isn't left around the foundations.

I've spoken to a couple of builders and also a building control officer about what may be causing the water to sit there and also ideas for a solution to resolve this. However, I've had conflicting advice e.g. DPC and concrete clay floor, raise clay floor level so that it is level with highest point of back garden, install a pipe to drain the water away to a soakaway...

I am thinking of laying a row of sandbags over the entrance hatch and then covering the entire hatch with tarpaulin. That way I should be able to work out if the water is entering via the hatch or rising up through the ground. If there is no water after a couple of weeks then I think I can lay a couple of course of blocks over the bottom of the hatch and then fix a gate. However, if water continues to collect in the 'paddling pool' then I will have to look at a more expensive solution. If so, would it be relatively straightforward to stick a DPC over the floor area and pour concrete onto it?

Any ideas with what is likely to be causing the water and a solution would be very helpful

 

[OneDove]

Untitled

• OneDove
• 26 Feb 2014
• 1

Conservatory base with access hatch

Untitled

• OneDove
• 26 Feb 2014
• 1

Sunken clay floor that fills with water

 

[maltaron]

It is quite normal for standing water under floors. as long as it does not rise above the DPC it will not cause any harm. (unless it is stagnant or supports frogs). However, your problem is different, looking at your pics I would say that the water is entering from the garden, it looks as if there is no step in the way. If you want to keep it dry for storage you should lay a bed of sand, the a sheet of 1200 guaqe polythene. A layer of concrete 50-75mm thick laid to a fall to either a sump or a drain to a lower point would keep it dry.(if a sump a pump with float switch would be needed). Some blocks laid on a foundation below base level and up to about 300mm above ground will stop water entering.