Static water pressure and house structural failure

Unless you design the walls to accept the pressure. This sounds a bit like the how long is a piece of string problem. Are you expecting frequent floods, if so then build some other place!

Brian

Usually given as 1 metre, but I have seen it specified as low as 75cm in one of the government flood leaflets.

"A structural assessment of the building is recommended where flood depths in excess of 300mm(about a foot) are intended to be resisted"

is of course a lower conservative depth

I think intuitively I would have said 3 foot, the consulatant probably quoted something like 18 inches for the 1920s construction houses under consideration. Makes you wonder about the residential doorway flood barriers often to 0.6m height plus the depth to ground level, but then you have to consider wash from vehicles that drivers , in their interest, have to go through flood water as fast as possible, not crawl along

Isn't it pointless quoting a single height? It's the length of unbraced wall that must surely be important. Small rooms with short walls will be stronger than large rooms with long lengths of unbraced walls

Tim

If the air intake isn't high up, the advice is to drive slowly unless you want to end up sucking water into the engine, locking it up solid and wrecking it.

I seem to remember it is the 2 separated skins that is the critical factor. Once the outer skin fails then the structural indegrity of the inner skin is prejudiced and so perhaps internal wall bracing, unless an unlikely 2 foot wide rooms, is probably irrelevant

During the 2007 floods most of the solid floored, newish houses in the lower parts of my village suffered water penetration through the damp proof course. Those with suspended floors and air bricks saw water appearing indoors from under the floors. Fortunately the water didn't rise high enough to affect my part of the village (thank goodness).

Depends.

I once had a solid wave across my bonnet from the **** in the 4WD coming the other way. He was OK in a foot of water. I was amazed that the engine didn't even hiccup!

I hear some cars have the air intake where it'll get nice clean cold air. Just behind the front bumper.

Andy

They put the engine that way round (air intake facing the front) in the early prototype Minis. The carb iced up during tests.

So they put it the other way round. And anyone who owned a Mini discovered that the distributor now got wet instead.

Also, with suspended floors, the depth of infill under the floor can be significantly below the outside ground level. In some cases, you will have used up your metre when water starts creeping up above the outside ground level. OTOH, successfully sealing against the subfloor space filling up is not normally very successful, so you are unlikely to put the wall to the test.

er parts of my village suffered water penetration through the damp proof course. Those with s

uspended floors and air bricks saw water appearing indoors from under the floors.

rt of the villa

ge (thank goodness).

Foresight on your part? Or is that taking the moral high ground?

Bill

I'm getting to query the viability of the property flood protection scheme going in local to me, for marine flooding. The houses that are lowest lying and have been flooded over the years, the water initially comes through the subsoil. To deal with that sump+pumps (mains powered) are going in but no one has got the protocols for flood-situations from the electricity utilities. It is likely , from one previous incident, that on first awareness of a serious flood situation the utility will isolate the relevant area at the local stepdown transformer, so no power for the pumps. A chain is only as strong as its weakest link. If there is flooding of just one property in the area that swamps the company side of the mains then presumably the local supply will cut-out via a mechanism in the local area transformer without any utility company human involvement, anyway.

BRE data on this topic seems to be behind a paywall, but open access (to USA data of course)

During the 1980?s, the USACE (US Army Corp of Engineers) conducted a series of tests on the structural resistance of brick facing walls and concrete block walls to hydrostatic loads (USACE 1988). A small range of wall configurations were tested. The results showed complete failure of the walls at flood depths of around 2ft (0.61m) for both brick and concrete block walls. Significant deflections of the walls began to occur at around 1ft to 1.5ft (0.3m to 0.45m). A test wall with simulated roof restraints withstood slightly higher loads. A picture of one of the test walls is shown in Figure 7. (picture shows depths quoted are to the bottom of footings , not ground level, but no upper story ) ... b) Whist the test walls failed at flood water depths of around 2.4ft (0.73m), this improved to around 3ft (0.91m) for tests on full scale dwellings due to the additional strength provided by the composite action of the walls and roof. Wall failure is potentially very sudden and catastrophic.