DIY Doctor

high water table cominin under floor boards

Postby eddylyons » Thu Nov 18, 2010 10:52 am

ive recently broughgt my first house and have discovered that there is a high watwer tablle here resulting in water under my floorboards. does anyone have any ideas how to water proof my house to stop it comin inside again, ive thought about a dpm and concrete??
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Simply Build It

Postby Perry525 » Thu Nov 18, 2010 8:13 pm

If you are writing to say that you have a puddle or even a lake under your floor boards? The key thing is, is it staying below damp proof level?

If it is, below damp proof course level, then there is no harm in leaving it there.

Are you on a hill? Is there the possibility that a hole knocked through a wall would enable the water to run away?

As your home may well have been built in a lake, there is little point in trying to pump it out, nor is there any point in spending lots of money trying to tank the space and waterproof it.

Because the temperature under the floor is low, usually below 10C/50F, there is no chance of any damage.
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Postby eddylyons » Sat Nov 20, 2010 2:57 pm

theres no damp course only engineering brick?? should i inject the wall and make new damp course?? also the water is causing the motar to deteriorate and u can wipe it out with ur finger. should i re point??? also i have serious amounts ofd white salts all over the brick. should i clean this off??? in some places the floor boards are rotton, but would a new damp course prevent it if i injected under floorboard level??/
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Postby ICL » Sun Dec 05, 2010 12:59 pm

It sounds like you have an older property. However I would be suprised if there were no DPC as these have been in use for a number of years.

Where engineering bricks are used the DPC is usually found at the junction between the engineering bricks below and the common bricks above. If the common bricks above the engineering bricks are dry then the DPC is intact and does not need replacing.

The white salts are called efferevescence and are as a result of salts being sucked up into the brickwork and evaporating on the surface. They are harmless and probably pointless to clean off in your property as they will only come back again.

As Perry525 has suggested there is no problem in leaving the water under the floor. Many older properties with wooden floors were constructed in this manner without serious side effects. However it is important to ensure that it is well ventilated to avoid creating a damp environment under the floors.

Make sure that all the air bricks that will have been built into the walls have not been blocked up by some previous DIY'r who did not realised that air vents under floors and in bathrooms/kitchens were put there for a reason other than to make the house cold.

The floor joists would have been built above the DPC level. I would cut them out and inspect under the joists to find the DPC. When replacing the joists I would use treated timbers and wrap the ends in DPC where they socket into the brickwork.
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