Depth of footings for porch

If it is just a deck not attached to the house with a roof over the deck I dont think you need to worry about depth you need only to support the weight and keep the deck from sinking. I used flat 2" concrete block, the deck has been fine since 72

Below the frost line and to solid ground.

Might be 50 feet in a swamp- but in relatively stable ground, just get below frost.

If you're pouring concrete, don't forget to make the base large enough.

Jim

It's attached. Soil is sandy loam..

Soil is sandy loam.

For me frost depth is 3 feet, my porch has been fine 35 years set at ground level on block, a 25 x 30 foot deck, so to just say below frost line is BS

At least 4 feet. Use Sonotube's BigFoot base if possible. At a minimum wrap the Sonotube in polyethylene to help keeping it in place in the face of frost heaves. Most decks don't weigh enough to keep a straight footing in the ground when there are frequent freeze/melt cycles.

By atached I meant a porch with roof. Go ahead dig down 4 ft and have fun but all you need is a pad, and wood should not touch concrete but should be bolted to special plates to keep it from rotting that keep it off the ground.

Sonotubes, yea right, bs , if he is building an addition ok, but this is a dam Deck, nothing more. Even small sheds you buy are recomended to have Pads, not foundations to frost. A fence yes, but not a deck.

He is in Wisconsin, and he says the deck is attached to the house. If the deck is attached to the house, it needs support starting below the frost line. Having a deck on surface pads heave a half inch or so during a Wisconsin winter will certainly un-attach the deck from the house, over time.

-snip-

To me, a deck is not a porch. You can attach a deck so it slops up and down with the frost. [I wouldn't- but you could] A porch needs to be rigid so the roof doesn't rip away from the side of the house.

If it is on bedrock, there isn't any frost heave, so you can get away with more.

But if it was mine, I'd go below frost and not have to revisit that job. On sandy loam I'd also want a huge elephant foot set on compacted crushed stone.

But that's just me. If there will be a permit involved, the only person that can answer the OPs question is the OPs building inspector.

Jim

-snip-

The reason sheds are allowed to have pads is because they float up and down & it doesn't matter.

Presumably the house stays in place because it has a foundation. If you attach something rigid to the house, it must not move up and down or it will pull itself away from the house.

Jim

rote:

Why not its a deck, and mine is fine after 35 years doing it, You dont have doors or windows to worry about I still say its overkill as I have had no problems. If it had doors or a roof attached to the home then it would need piers.

It's an attached porch with roof. Not a deck! I never mentioned deck. No idea where this came from.

It's a porch, NOT a deck.

Go take out a building permit, like required. And while you're there you can ask the building inspector. He/she may not give you an answer, but an architect will.

Around here the building inspector has taken a liking to the earth screw ground anchor. Screw down below frost line. I used them for my decks a few years ago. No movement at all.

The link just shows the general idea.

They're called ground hogs around here. Home Depot has them.

LdB

Sorry, I thought Deck, a porch with roof needs support below frost line.

I am in SE Wisconsin, and I believe that my local inspector made me go

JK

Here in Iowa that's about what it is too. It is because the inspectors want them to be below the frost line.