How can I build an underground room in a wet environment?

Question

I live near the coast, and I need info on building an underground room for storage. The ground is really wet here, and I would like my room dry. How can I build a room in this environment? I thought about just digging a hole and using concrete block to frame everything, and a concrete floor, and pouring mortar in the holes of the block. Will this keep out water? What else can i do?

Where can I find information on this?

Answer 1

Listen to dogsafire, especially if the building is below the actual groundwater table, you could be facing some serious problems.  I'd reccomend finding an engineer to look at the thing before you actually build it.  If it isn't actually below the groundwater table and it is just water seeping up above, then you might be okay with just putting a membrane outside, but if not, and you build it, you could face some potentially serious problems.

Answer 2

It's not just about keeping water out, it's also about keeping your structure from popping up out of the ground. As you are aware, very, very heavy objects, such as supertankers, can be made to float if they displace a sufficient amount of water. Well, the structure that you're planning on building will displace a lot of water and if that water weighs more than your structure, then your structure will float, that is, it will simply start rising up out of the ground. If the water level then drops, your structure is left unsupported.

The solution is to place a drain system outside of the foundation and pump the water away from the foundation as it accumulates. Not very pretty, but at least your building will stay pit. You should still seal the concrete to keep the walls dry.

Answer 3

3 ways:

1) build an underground drainage system on the outside of the concrete (underground).  But, you have to find a lower point for the water to drain to.

2) Seal the concrete blocks with a number of products for that purpose (go to your local home-improvement store and ask for specific products).  Unfortunately this will not be a permanent solution -- the sealants will eventually fail when the concrete develops small cracks.

3) make a sump in the floor, let the water seep in and drain to the sump and use a sump pump to pump the water out.

4) a combination of 2) and 3) would be best if you can't do 1).

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