DIY Footings for a small cabin ??

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DIY Footings for a small cabin ??

Postby koastal » Tue Apr 12, 2011 2:33 pm

Hi,

I need some tips on how to set out concrete pad footings for a 6m x 12m rectangle bungalow. I am relatively handy with tools and I am considering having a go at building it myself.

I did the deck on my front house back in Australia ( see below ) however it was a very easy project as the house was there already ( duh ) so I had a floor level to work to and there were only two parallel beams to level up before dropping joists on top so I just used a straight piece of timber and a level to keep checking ! EASY.

Image

See below for the kind of set out I need to get my head around. I can buy the little concrete square pads here pre-cast or i can use pipe / buckets like i did for my deck .

Image

However.....if I am spacing the footings at 2m then i think i need 4 rows ( the 6m width ) of 7 ( the 12m length) = 28 footings and I have 0 idea how to go about this logically and easily so I end up with the beginnings of a level bungalow !! My land is fairly flat so there is minimum digging required. I am guessing i need to get the corners / square right first and then work from there ?

Also - how do I connect beams to the pads pads ??

If anyone knows of any good books or websites or videos please let me know.

thanks
koastal
 
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Re: DIY Footings for a small cabin ??

Postby koastal » Tue Apr 12, 2011 3:21 pm

and....at the risk of being ridiculed ! :oops:

Is it feasible to use something like OZPOST or similar post anchoring system for a bungalow this small ?

http://www.ozpost.com.au/ozpost_applications.htm
koastal
 
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Re: DIY Footings for a small cabin ??

Postby geordie » Tue Apr 12, 2011 4:13 pm

kostal the forst job you need to do is run two lines paralell for front and back wall
now put a strings across for the end wall,s again paralell
to get them square measure from corner to corner diagonally so you should have a square with a cross corner to corner with the measurements all the same EXACTLY the same
what i do at this point is extend out a few feet 2mtrs in line with the walls and hammer a stake into the ground leaving an inch 25mm up out of the ground and make reference points
so eight stakes in total that when you hang a line and measure in 2mtrs should be dead on the corner of your building but the stakes are far enough away to not get moved dug out or damaged
Next you need to place the footings it looks like you are building with wood/bamboo so how deep is your decision how thick the same its not a lot of good asking how to attach a post to a concrete slab without knowing what the post is and why use precast slabs???
the idea of a footing is to place it in SOLID ground to SPREAD the load of the building given that your building weight wise equates to a garden shed ???
i personally woul do as the thais do dig down 600 mm 300mm across put in the post and concrete then bring it up to ground level with concrete and pour a 150 mm thick slab so you are creating an upside down tophat in the ground with posts out of it more work but less of them the thais use them at 12ft/4mtrs
decide what height above ground you want the floor and start laying the bearers for it ataching them to the posts
There was an interesting build By AUSSIBOY ? where he did a detailed build but i cannot remember where when how but similar using plywood corrugated iron and steel c section for the floor
If you want to use c section you can use standard bolts or look for Teck bolts (roofing bolts)
either with a self drilling head or normal wood screw head i have used them over there from the local builders merchant
my comments may be wrong but never deliberately
If it aint broke, dont fix it
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Re: DIY Footings for a small cabin ??

Postby koastal » Tue Apr 12, 2011 4:47 pm

the forst job you need to do is run two lines paralell for front and back wall
now put a strings across for the end walls again paralell
to get them square measure from corner to corner diagonally so you should have a square with a cross corner to corner with the measurements all the same EXACTLY the same

GOT THAT

what i do at this point is extend out a few feet 2mtrs in line with the walls and hammer a stake into the ground leaving an inch 25mm up out of the ground and make reference points so eight stakes in total that when you hang a line and measure in 2mtrs should be dead on the corner of your building but the stakes are far enough away to not get moved dug out or damaged

KIND OF LOST ME THERE

Next you need to place the footings it looks like you are building with wood/bamboo so how deep is your decision how thick the same its not a lot of good asking how to attach a post to a concrete slab without knowing what the post is and why use precast slabs???

YES I WILL BE BUILDING ALL THE FRAMING ETC WITH TIMBER.

the idea of a footing is to place it in SOLID ground to SPREAD the load of the building given that your building weight wise equates to a garden shed ???
i personally woul do as the thais do dig down 600 mm 300mm across put in the post and concrete then bring it up to ground level with concrete and pour a 150 mm thick slab so you are creating an upside down tophat in the ground with posts out of it more work but less of them the thais use them at 12ft/4mtrs

GOT THAT ! SO I WOULD ONLY NEED 12 FOOTINGS . U R SAYING I CAN SINK THE TIMBER STRAIGHT INTO THE CONCRETE ?? IS THAT OK ?? AND THEN I JUSTMAKE SURE THE TIMBER IS LEVEL / STRAIGHT AS IT DRIES ? NOT QUITE SURE ABOUT THE "15CM SLAB" PART OF THE TOP HAT ? THIS IS THE DEAPTH OF THE 300X300MM "PAD"
decide what height above ground you want the floor and start laying the bearers for it ataching them to the posts

GOT THAT !

There was an interesting build By AUSSIBOY ? where he did a detailed build but i cannot remember where when how but similar using plywood corrugated iron and steel c section for the floor

FOUND IT !

If you want to use c section you can use standard bolts or look for Teck bolts (roofing bolts)
either with a self drilling head or normal wood screw head i have used them over there from the local builders merchant[/quote]

THANKS VERY MUCH FOR THE HELP !
koastal
 
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Location: Phnom Penh, CAMBODIA

Re: DIY Footings for a small cabin ??

Postby geordie » Tue Apr 12, 2011 7:15 pm

i find it invaluable to make permanent reference points
simply extend the line,s 1mtr 2mtr 3mtr = beyond where the corner is that way when you dig out all the holes you hang the lines back and know where your corners are
Buy some nylon rope for getting your posts plumb
Use the rope as you would on a tent as guy ropes tie them to the top of the posts and by ajusting the rope around a stake in the ground you can plumb them and concrete around the posts
My sugestion of a slab on top (ground level ) is to minimize digging or dig 6" 150mm into the ground and fill with concrete 600 minimum square at each leg if you are using wood great
hammer a few large nails in to the wood before you concrete so the wood if and when it shrinks will be firmly retained by the slab which is ther to stop the post sinking when the ground becomes soaked it turns to mush over there so try and stop the water penetrating near to the posts so a mtr square would not hurt but its hard work by hand ??
Thats the upside down top hat??
Put a good long overhang to take the water away from the house
Treat the timber before and after installation there will be loads of areas you cannot get at once its built for the posts you could try and get an old 45gallon drum and soak the posts in your chosen preservative just dig a hole that you can bury the drum down at ground level
and stand the posts in it for a couple of days should last a few years then
my comments may be wrong but never deliberately
If it aint broke, dont fix it
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Re: DIY Footings for a small cabin ??

Postby canopy » Wed Apr 13, 2011 7:10 am

A footing that is too shallow will result in the post punch shearing through it. A footing with insufficient surface area for the soil below and weight above will sink. A footing that is too big or deep is simply wasted materials and money laying in the ground. Do the engineering calculations that assure all the margins are there to make sure you get this right. And remember concrete needs 1 month after pouring to reach its full strength.

Concrete wicks moisture which will rot posts so install a moisture barrier. It's also advisable to have a roof overhang to keep the posts dry. Lock the posts to the footings so they can't move.

To get the footings lined up dead on, batter boards are often used because they allow the string line to be tweaked. See google images.
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Re: DIY Footings for a small cabin ??

Postby geordie » Thu Apr 14, 2011 2:50 am

batter boards being permanant reference points as i refered to above i usually bang a stake
low into the ground but the line configuration is what i was trying to describe and i like to keep it at least a mtr off the corner so not likely to get stood on
my comments may be wrong but never deliberately
If it aint broke, dont fix it
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