Building under a house on the cheap.

[Fantapantz]

Not a timber question but you guys might have some ideas that the money pit (read future architect) might have forgotten, and the more I can do on CAD the cheaper he will be.

Situation: House on 76x76 RHS 4mm wall. I want to extend some(half) of the posts and excavate downstairs.

Questions:
1. Is it possible (read legal) to weld an extension on with an inner sleave bolted above and below the weld area?
2. Is it possible to weld brackets onto the posts to support bearers for the lower floor

Fifteen posts and I want to do this on the cheap, without the house falling over........Whoever built this house has already left out four posts and two bracing straps. I thought the plans the council had were supposed to resemble the house.

[journeyman Mick]

Generally speaking welded joins are legal, BUT, they must meet standards for welding, the extra length might put you into a different range as far as the size/wall thickness required. Extra height will almost certainly mean extra bracing. Ask yourself if you really trust your welding that much. If you excavate near/around any of the post footings you will need to redo the footings as well, ie: prop house up, cut bottom of post off, dig out footing, excavate for lower floor, excavate new footing, extend post, pour new footing. This is serious stuff and you need to take lots of photos and your house plans to an engineer before you start to see whats feasible. Anything's possible, but not everything is viable.

Mick

[Grue]

I don't know if its pissable or not but you may get some guidance from a FAA publication AC43.13-1b. There is a section in there about tubular repair and it will give you some ideas on how to do a properish job.

The document is downloadable in PDF format from www.moneypit.net/~pratt/ac43/
look at the index and get the section on welded repairs.

The other sections are interesting as AC43 is a repair manual for aircraft without a repair manual. i.e. if you build one in your dungeon/cellar/garage then you are required to build and maintain it in accordance with AC43.

Grue
www.metalbashatorium.com

[colh]

stretching the brain back 20 years to my basic engineering theory .....

If you set out to make your columns longer, you need to be careful of the ability of the longer columns to resist buckling. Buckling resistance is a function of the length of the column between supports (ie the top, the bottom and any intermediate bracing) and the bending strength (ie diameter/size and wall thickness). If you are using rectangular sections, the ruling dimension for buckling is the smaller side.

I am sure I have seen brochures and building guidelines that tell you the size of columns to use for given length and spacing. Try Lysaghts or Tubemakers or Blackwoods or a building information centre.

It might end up easier and more reliable to make up new, longer and heavier columns and replace the whole column rather than trying to extend the ones in situ.

I took out a number of brick columns up to 8 feet high and replaced them with 4 inch heavy wall steel pipe (which I happened to have).

cheers

Colin

[Fantapantz]

Thanks guys........have decided to buy new posts...........Stuff the expense.

If we build under a deck area, how do you go about sealing the roof/making a roof that doesn't get covered in dirt/mud thats fallen through the decking, if its possible?

All just ideas at the moment:confused:

[pyro_15]

I'm thinking of doing something simular and would also like your opinions, my columns are currently at 2130mm and i'm thinking of extending them to 2400mm (ie 270mm extension) but rather sleave, i was thinking of having a "mini" column made up. ie a column with the top and bottom plate the same as the top plate that is existing. Then bolting the mini column to to top of the existing column and then having a welder run a weld around where the two plates meet.


---------
/ / mini coulmn
/ /
--------- bolt and weld these 2 plates together
---------
/ /
/ / existing column
/ /
/ /
---------

i was thinking either this or cutting off the old columns at ground level (as they are concreted into the footings and slab) and installing 2400 long ones with the same type plates and dyna/chemical bolting them into the existing footings/slab.

The first option is cheaper easier and quicker, The second option would be better (less joints the better in my experince as an electrical worker). But I wonder is bolting to an existing footing ok? rather then having the column bedded into the footing..

your opinions positive and negative would be appreciated

[pyro_15]

my little diagram didnt quite work, the "pole" bit was shifted to the left, its suposed to be centered to the plates.