Sub Floor Excavation

[Miles]

Dear All,
I have this terrible desire to dig out under the master bedroom and make a wine cellar. I know it will cost me a fortune , be a complete nightmare, but I can't resist the urge! The room is about 4000 x 4000 with external brick veneer walls on two sides. I'd have to dig down about 2 metres. The piers would be removed and bearers reinforced. Obviously , I'd get an engineer to look at it, but I wanted to know roughly how far in from the footings of the house I'd have to build the retaining wall. I thought if it was more than 1 metre,the cellar would be too small and it wouldn't be worth it.

[silentC]

I think a rule of thumb is to take a line at 45 degrees from the base of the footing to the desired floor level, and that gives you the distance out from the footing. So if your footing would be 1 metre above your floor level, then you would be 1 metre out into the room.

However, if you get an engineered retaining wall designed, they can probably do better than that.

But that's a rough guide that an engineer gave me once.

[les88]

I have seen these excavations cause a lot of grief. The house is built on strip footings and the sub soil is what? when you disturb the sub soil the ground water pattern can change. I saw one excavation that after a lot of heavy rain the soil kept falling in the hole, the only way to stop it was to fill the hole with tons of brick bats and broken tiles. I suggest buy a large wine fridge.
les

[echnidna]

I think a rule of thumb is to take a line at 45 degrees from the base of the footing to the desired floor level, and that gives you the distance out from the footing. So if your footing would be 1 metre above your floor level, then you would be 1 metre out into the room.

However, if you get an engineered retaining wall designed, they can probably do better than that.

But that's a rough guide that an engineer gave me once.

Thats the right way.
Any closer will need engineered retaining walls

[Pulse]

Miles as Silent said you have a problem if you disturb the bearing area of your footing. 2 metre ceiling height will not be possible cheaply. You would have to be at least 1500 from the footing bases (assuming the footings are 500mm below ground level)

Better idea is to dig a shallow cellar that you can crouch in with a central depression. Like this:

Cheers
Pulse

Note the expensive way is to bore piers on the borders of the cellar and concrete fill, might add $20K to house price during construction, let alone with no access.

[ozwinner]

Or, you can underpin the brickwork, that way your outside wall in still in line with the brickwork.

Al

[journeyman Mick]

Or you could take off the roof, ceiling, floor then drive sheet piling down flush with the walls. Then you could excavate, build your (waterproofed) retaining walls, backfill and compact then rebuild your bedroom.

Okay, probably not financially feasible , but entirely possible .

Mick

[pawnhead]

Okay, probably not financially feasible

The hydro set up that he's got planned for it should more than cover the outlay.

[mick101]

I have seen these excavations cause a lot of grief.

I knew a friend in syd that had a beauty cellar below but man it cracked his house in two. It would open & close the bricks at will depending on the weather.

[Miles]

Thanks for the repies, Gents. Pulse's idea of a central "walkway" sounds feasible. But still ,I can't stop lying awake at night thinking of building some sort of European style "dungeon" under the house!

[patty]

come on miles we dont need to worry about any of your kinky fanatasies

I think pawnhead is more on the money

No seriously mate that is a heck of alot of dirt to move can you get access? you have to weigh up the costs and see if it is going to be worthwhile exercise I was planning on doing something similar I live on a slope and the idiots who built the joint cut into the ground but never retained the dirt and when it rained all the seepage and water washed around the brick piers so the former owner decided to get some fill pumped in and rest it against a partition wall that was not designed to take the load so with no access I had to dig it out by hand 900mm wide 1.6mtrs deep x 17 mtr long and put in a retaining wall what a nightmare of a job plus all the agg pipe and drains I had to replace they used old terracotta pipe at the bottom of the footing as agg pipe and it was clogged with mud so I had to replace that as well not fun....but if you have access without destroying the house certainly consider it