/diy/ - Do It Yourself

[Anonymous No.1545294]

Hey /diy/, i'm looking to design some concrete foundations for a sign in my paddock, but I don't want to dig up the existing ground and pour the footing. Instead, i'd like to simply place a pre-cast foundation on the ground and bolt the sign posts to it.
Pic related.
Would this be possible? Is it the same as designing a foundation below ground? Will the sign fall and end my suffering or will it stand strong?

[Anonymous No.1545314]

it seems with a wide enough base it would never fall relative to size of sign.

[Anonymous No.1545321]

yeah that should work. though I would cast the pipe or stand into thr concrete unless you want it to be removable, then use wedge anchors or cast in place bolts

[Anonymous No.1545401]

>>1545294
That actually looks retarded and I hope your sign falls over after some wind catches it.

[Anonymous No.1545433]

>>1545294
>I dont want to secure the structure to the ground. Anchors are gay, bro
Enjoy your death lawsuits....bro.

[Anonymous No.1545584]

>>1545294
b-but wind?

[Anonymous No.1545705]

>>1545433
Anchoring into the concrete isnt an issue using cast in place bolts
And it should be stuck to the ground the same as a regular buried footing, since friction between the sides of the footing and ground would be neglgible anyway

[Anonymous No.1545883]

>>1545294
It depends on the soil and the area but, even for the shallow foundations, you never build at the original level of the ground because in order to achieve a necessary durability you need to reach the layers of soil unaffected by the seasonal variation of the water content (below the frost line) and that are below the topsoil layer (where grass grows). And of course it has greater bearing capacity.
When you consider wind the ground above contributes to the supporting capacity only by virtue of its own weight (soils have very bad tensile strength). So if you go with a slab-on-grade foundation what keeps the sign there is just the weight of the foundation itself (not much help from the ground). Anyway you should be able to find on google guides to design sign structures BUT It's not easy at all, I'm studying it right now. Ask an engineer for help

[Anonymous No.1546114]

>>1545883
>you never build at the original level of the ground because in order to achieve a necessary durability you need to reach the layers of soil unaffected by the seasonal variation of the water content (below the frost line)

the thing is op, whenever you see an above ground slab doing any kind of work its just to spread out some load so it doesn't sink into the ground.
you never really see it used to hold down what you have, which is essentially a great big fucking sail on top of a lever.
digging up the ground is absolutely the least of your worries, and if you can't even be bothered to do that then i dread to think what the rest of your plan is.

you seriously need a competently designed foundation to hold this thing up, its not a garden shed sitting on a few cinder blocks it looks like serious fucking buisness.
what is this a full fucking billboard? what are the dimensions?

this is the kind of thing where we also need to know where you live because the variation in wind is going to be a major fucking factor.

because of the forces involved you are absolutely going to need proper structural support in that pour too. calculated support, not just made up in your head.

this is a proper structural engineering project.

i mean i'm assuming its a billboard size thing, if its a mailbox or some shit then who cares do what you like.

[Anonymous No.1546126]

>>1545294
it will work but you need way more concrete and bigger base
easier to use tiny cast in ground base and four around it with steel cables or anchor it to trees

[Anonymous No.1546817]

>>1545705
Not sure if bait.

[Anonymous No.1546818]

>>1545294

[Anonymous No.1546825]

>>1545294
>Would this be possible?
Yes, but it would never pass a county or city engineering department approval. If discovered after construction it would be condemned and you'd be forced to tear it down.
>Is it the same as designing a foundation below ground?
No. Resistance to wind forces would not be adequate, even with a ridiculously large base you'd experience settlement and have zero resistance to lateral loads.
>Will the sign fall
Yes. bearing capacity failure is possible from founding on topsoil and soft and saturated surficial soils. Signs of this size are usually on piers down to rock. If you build a large pedestal base you will have greatly increased construction costs over digging a footer, but youd have to have addittional top and bottom steel in the concrete to resist footing structural failure. Being a large "sail" it will catch all the wind, as well as uplift forces, and eventually lead to an overturning failure, or since there is no side wall or resistance to errosion sliding failure is also very likely.

It's a grab bag of bad things to choose from.

[Anonymous No.1546844]

>>1545705
Breh, you absolutely must be a chink if youre truly considering this route.

[Anonymous No.1547009]

>>1546825
I feel like most of these issues would only be for a large billboard. The sign i'm thinking of is only 3m by 3m. Similar ones have been grantef approval with above ground foundations