Hello everyone glad to be able to have a great resource such as this to draw some knowledge from. Was hoping to get a little help with a few ?’s I have about fill.
I am about to do a portico addition with stone veneered steps and landing here in the upper Northeast where the frost is deep enough where we go 4′ to stay below it. The portico will be connected to the home. I’m sure the fill about the existing foundation wall is “drainage fill”. Sandy gravel. When I get down to the elevation I need do I just compact and form my footings or is it necessary to dig until I find solid clay or other layer of earth?
Thank you for any thoughts you may put my way, – Dawg
Replies
Probably shouldn't put footings on anything other than undisturbed earth, or "suitable compacted material".
And unless you're certain that the drainage material is suitably compacted, it will probably settle, leaving your veneered steps leaning.
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Would you say that suitable soil would be compacted drainage fill?
I know that the 8' foundation wall will have drainage fill all the way down to the footing to where the perimater pipe is. I only want to go 4' down below frost. The house being 20+ years old the fill will have compacted some.
I guess I am worried of having to continue digging down to a depth of 8' to hit solid pact. Then adding and compacting the soil until I hit my footing grade.
In anyones expirience is 25 years enough time to pass for the fill around a foundation to compact to where I might just dig to the footing grade, compact the area and start building? Thanks,Dawg
>> The house being 20+ years old the fill will have compacted some. << I'm thinking that settled and compacted are two different things.
Also, you might want to consider pinning the new foundation to the old.
Honestly, if this is to be connected to the house, and you're looking to pour a perimeter foundation for the portico, you have the two limitations you've already addressed: undisturbed soil and frost depth.
I'm in CT, and what I'd recommend is a stepped foundation.
Near the house, excavate down to the depth of the house's footing existing, probably 7'-8'. Stay at that depth until you get 3'-4' away from the house, then "step" the excavation up to frost depth, the roughly 4' that you already mentioned.
Trust me, it's not what you want to do, it's not what I want to do, but for something attached to an existing structure, it's what we both have to do.
Mongo
yup yur right Mongo. Not really what I want to do..... I'm having nightmares of the new foundation bearing on the existing foundation wall and causing problems down the road. I was going to pin it to the wall and realize that this just might cause more problems. I suppose at that point I could have an expansion joint of sorts at the existing foundation and and not attach it at all...... Thoughts? Thanks guys,Dawg
<I>I'm having nightmares of the new foundation bearing on the existing foundation wall and causing problems down the road. </I>Consider going down just 4' for the entire wall. If the soil nearest the foundation were to compact/settle under the weight of the portico...which it will...then over time it'll do exactly as you fear. It'll "tilt" in to the house, putting lateral pressure on your existing foundation wall.Remember, the existing soil against the house is settled, not compacted to the same state as naturally undisturbed soil.To "do it right" you'd have to dig down to the depth of the existing footing and re-fill and compact in lifts. Well, while you're down there, you may as well form up and pour a stepped foundation! No worries with that route.If you go full depth and place a new footing at the same depth of the original...no on top of it, but next to it...and pin the new wall to the old, you'll be in fine shape.Trust me, I can relate to this one. More than once time I've wondered it I could "get away with it."Time has a way of showing us our errors. And making us pay for them!Best of luck with the project.