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I am starting an addition on our lake cabin. I need some advice. The addition is going to be approximately 19X28. My problem is i am not sure i can do a slab foundation. The reason is this. Corners A and B will be attached to the existin slab. Corners C and D will be the 28 ft ends. During this 28 ft, there is a decline in elevation. On C corner, it drops to 16"...On D corner it drops down to 30". The books i have read say that you can only fill up to 24" with sand or sandy loam type dirt. Less than that with gravel. The grade is iron ore. Very solid, but i am afraid of the 30" drop. My question is how do you handle this? Any help will be appreciated.


Craig
 

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Very few contractors design foundation systems - they just build what an architect or engineer has specified. You're asking for advice about an issue that is more a design concern than a construction question.
Keep checking back. You might get a hit.
 

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PipeGuy said:
Very few contractors design foundation systems - they just build what an architect or engineer has specified. You're asking for advice about an issue that is more a design concern than a construction question.
Keep checking back. You might get a hit.

If you have any concerns about a foundation, hire a good civil engineer. If you have any concerns about soil conditions, hire a good geo-technical engineer. Keep a close eye on your general contractor and your mason to make sure that it gets built the way it's supposed to. Trust me on this...
 

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check out this website

In my oppion the best foundation you can put in a house comes from this company. www.superiorwalls.com. This is what This old house went with on there current project. They definately know what there doing. :Thumbs:
 

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With the 30" grade drop it comes down to whether you want to spend the money on fill for the slab or excavate the entire area for a crawl space. Either way, the engineering is in the turned down footer more than the slab. How deep were you expecting the turned down footer to go? 24"?
Iron ore? are you in Minnesota?
 

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747 said:
In my oppion the best foundation you can put in a house comes from this company. www.superiorwalls.com. This is what This old house went with on there current project. They definately know what there doing. :Thumbs:
I hear the big disadvantage to precast is that you have to have a crane on site, and that alone adds to the bottom line pretty dramatically. Other than the extra cost I hear that precast foundation walls are superior in everyway to every other type of foundation system.
 

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Can you pour a stem wall footing then backfill and compact to grade the interior slab subgrade? I've seen it done, but unsure of building codes in your area.
 

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IN CALIFORNIA, PERHAPS THE HARDEST PLACE ON EARTH TO BUILD , IF THE CONC. IS 36" OR UNDER IT FALLS INTO CONVENTIONAL CONSTRUCTION STANDARDS. THEREFORE NO ENGINEER WILL BE REQ. F.Y.I. A CIVIL ENGINEER ISN'T GOING TO BE ABLE TO HELP YOU (UNLESS YOU WANT OVER ENGINEERING TO COMPENSATE LACK OF EXP.). IF IT IS NOT A CURB OR A GUTTER GET YOURSELF A STRUC. ENGINEER. ABOUT 75CENT A FT. WOULD BE A GOOD BASE FOR AN ENGINEER

Very few contractors design foundation systems - they just build what an architect or engineer has specified........ NEVER HAS A STATEMENT BEEN SO WRONG 1. AN ARCHITECT IS NOTHING MORE THAN A HIGHLY (HIGHLY) OVER-RATED DRAFTSMAN (YOU KNOW TREES ARE MORE IMPORTANT THAN SAY ... A HOT WATER HEATER) 2. AN ENGINEER CAN'T SPECIFY ANYTHING WITHOUT A SET OF PLANS FIRST (50% DON'T KNOW HOW TO DRAW PLANS AND THE OTHER 50% WILL TRY TO AND CHARGE YOU OUT THE WAAZOO).

IF YOU DON'T LIVE IN CA. OR FLA. THERE IS A CHANCE YOU WILL NOT NEED PERMITS OR A PLAN.OR YOUR BUILDING DEPT. MAY STILL ACCEPT PLANS ON A NAPKIN (NO REALLY!), BUT IT SOUNDS LIKE YOU ARE IN THE MIDDLE OF NO-WHERE. ON THE SIDE THAT SLOPES THE MOST A 16" FTG. WOULD BE MORE THAN ENOUGH. ON THE OTHER HAND WHY GO THROUGH THE TROUBLE BUILD A RAISED FOUNDATION AND HAVE A NICE WOOD FLOOR :Thumbs: 12" FTG" 1 STORY (SLAB OR SLAB W/ 1 WOOD FLOOR OVER). 16" FTG" 2 STORY(TWO WOOD FLOORS) TYP. THESE ARE GOOD FOR EARTHQUAKE ZONE 3&4 SO IT SHOULD BE GOOD FOR YOUR APP.

F.Y.I. IF YOU CAN'T READ PLANS YOUR NOT A CONTRACTOR :cheesygri
 

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Roflmao :cheesygri :cheesygri
 

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If you think Supersteve makes no sense here, take a look at his website http://www.hughesdraftinganddesign.com

On his site he suggests that architects don't know much about constuction: "To design a home you have to know what goes where and that #6 re-bar is a ***** to bend." I really got a kick out of that. I was detailing and supervising precast concrete even before I got my license 35 years ago. He has obviously never worked on a job big enough to have a real structural concrete beam.

Hey Supersteve, you can't span much with #5 bottom steel!

He has probably only seen rebar used for temperature steel in concrete foundations where the foundation sub bends the bars by hand on site.

Hey Supersteve, you can't bend structural steel on site, it would take forever even if you had a machine that could do it!

He needs to get past the home hobbycraft level before he shoots his mouth off about trained and licensed professionals.
 

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I recently made contact with a drafting specialist that I'll be working with as a part of a neighborhood pool renovation. He's been able to earn a good livinng, for many years, doing industry specific drawings. I think his success can be attributed to both his technical skills and his understanding of the role he can play in the process. While he doesn't hold himself out as a design specialist, architects have come to recognize that his extensive practical knowledge and acceptional drafting skills can be a valuable assett to them in the building process. For that reason, he's always busy. Supersteve might do well to rethink his approach.
 

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supersteve probably should have read the date on the post that he responded to...March, and realized that by now, Oct., this problem had been resolved.
 

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I will assume that your existing structure is built slab on grade. Quite unusual if your in a freezing climate. To support a concrete slab where the existing ground is 16" deeper, I would scrape any organic material(topsoil) and fill with 1" crused or fractured stone to your subgrade. The stone will need to be spread out away from the slab to creat a gentle slope away. It's a solution that I dont like. It's prferable to do the right thing and support your new slab with a footing below frost and foundation wall.
 
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