If I laid a 4ft wall of concrete around my house, would that keep out flood water?

Lets deal with this sensibly! First, we have all been to the sea side and seen walls to keep out the sea!

Second, in many places alongside rivers there are properties with walls outside to keep out flood water and, many have steel waterproof doors to enable access. Third, you can buy simple traps that fit into your sewage pipe and, automatically close when water/sewage flows the wrong way. There are also more robust screw down valves that completely close off the sewage pipe.

So yes you can do it!

Talk to the Environment Agency to see how high flood water has risen at your address - then add on a bit for luck.

Interesting question, with many variables.I would guess the water would eventually try to under mine the wall as it rose higher. To make it more efficient I would construct the wall with part of it under ground like sea walls, most of them have more under ground than above. With out the tidal forces I would guess one foot would be sufficient but that's an engineers call and I'm not an engineer. As far as a door I wouldn't even try just use a ramp.

If you were fortunate enough to successfully build a waterproof wall around your house, you still have to worry about the toilets backing-up the sewer. The answer is NO

Even if you built a 5 ft wall and somehow managed to install a non-return valve on the sewer, you have to worry about the pressure........64lbs per one foot depth x 5 =320 lbs of water pressure on the wall !!!!!!

Slight problem,,,,how would you get in and out, you would need a gate...what if water rose to over 4' the neatest thing I saw was a metal insert that went into the door jamb on either side with rubber seals on the side which made the whole door area waterproof...saw them on TV years ago, but never heard from them again., you just slotted them in the doorway and that was that...great idea.

no the ring of concrete would not work ..unless you excavated down to a metre deep ..then you would have to shutter for the walls above ground and add considerable reinforcing steel above and below ground ..and the bricks below the dpc on a house are either semi engineering bricks or full engineering bricks (blues)..

You could do but you will need a ladder to get over of the wall, and if it does flood up over 4ft you will have your own swimming then.

I don't think so. I think you have to change the grade of the land around so that it slopes away from the house almost like you're on a little hill.

could work i suppose as long as the flood water rises to less than 4 feet!

Damp Course.

a basic wall will not withstand the pressure that flood water would put on it, if it was that easy wouldn`t it have been done allready