Footer & Foundation Design Help

[NWOhioChevyGuy]

OK, I'm in the design phase of the project and being an engineer I like to have everything infront of me before I move forward. That being said I also like to do it myself, as I'm my biggest critic, do it right the first time.

I know the plan that I will be ordering for my garage, it is a Behm Design 1476-3, 28' x 32' with engineered attic trusses for room / storage above. (plan will be modified to have 3'-4' between the garage doors)

I talked with my building inspector yesterday and he informed me that my footers need to be down to 42" here in Seneca Twp. Michigan.

Can any of you direct me to a site or resource that is a footer/foundation 101 course?

I have helped many times with pouring footers but never on the design side and I want to work up some costs on doing it a couple ways.

A) Poured Walls
B) Block Walls
C) ICF Walls

But first I need to layout the footers so I can figure out the material costs and then contact my "friends" most of whom do trades and see who can help with the different options / designs.

 

[PAToyota]

You are an engineer and cannot do simple foundation calculations?

 

[NWOhioChevyGuy]

My degree is in Environmental Engineering, and now I'm a Regional Sales Manager for Filtration equipment, so very little if no civil design experience, I actually had no civil classes.

I know that the design and layout is simple, I just want a resourse that gives the information to me in a concise document.

 

[PAToyota]

Sorry, just messing with you.

And you'd likely want structural engineering rather than civil....

On the scale of what you are doing, most of it falls to rules of thumb. Unless soil conditions are unstable or unsuitable, a basic two foot wide by eight inch deep footing with (3) #4 bars longitudinal and #4 cross bars at 16" will be more than adequate. A lot of contractors will argue that for residential construction you really don't need the steel. But you're talking under $500 to do it right when you are likely spending many thousands of dollars total. You know what they say about a good foundation...

 

[NWOhioChevyGuy]

I figured as much, no problem here, I played engineer for 11 years and decided that setting at a desk was not my thing. Designing nuts and bolts got really boring so I jumped to the techinical sales side of things and well it's not boring. Have to sell something to eat and keep a roof over the families head. Right move or not? still asking myself that question.

OK back to the garage.
I will be attaching this garage to the existing house via a 12' x 12' foot entry way that will enclose a laundry & mud room plus entry to the house, garage, from exterior. House was built in 1845 w/ a granite field stone foundation, when I key my footer and foundation to the house should I just drill and epoxy the bar into the stone? Or do they make an anchor system for attaching rebar to an existing wall?


Thanks in advance.
Keith

 

[PAToyota]

Drill and epoxy would work fine.

However, if there is any chance of differential settlement I'd look into an expansion joint at the connection.

 

[Franz©]

Drill and epoxy would work fine.

UNLESS you're doing a tunnel ceiling in Boston!

 

[burger]

A) Poured Walls
B) Block Walls
C) ICF Walls

by poured walls, do you mean monolithic slab?

i went with a monolithic slab, and probably would not do so again.

in my area (south jersey), my minimum footer was 32" deep x 8" wide. it seemed a whole lot cheaper to pour the monolithic slab, except for two factors i hadn't counted on:

1. i couldn't find an excavator bucket narrower than 12", and even that dug wider than 12"

2. the dig was little sloppier than i expected. there's probably at least a yard or two of concrete that went into the excavator's oppses.

i don't know if your were thinking monolithic, but just me, i'd do at least 3 courses of block above grade and pour the slab inside that.

let's not forget that my sill plates (and framing and siding) are all at ground level where they'd just love to rot away with merry abandon.

 

[PAToyota]

UNLESS you're doing a tunnel ceiling in Boston!

Just have to make sure you use the CORRECT epoxy... Which it turns out that they did not.

Also, epoxying something in horizontally to keep from having it settle differently is much different from epoxying something in to suspend it...

 

[NWOhioChevyGuy]

By poured walls I mean formed and poured just like a basement foundation. I would do a monolithic on a stand alone shop but not an attached garage that is on the house.

Regaurdless of the walls the pad will be poured inside the option I choose, as the walls will be done up to the height of the existing house floor to make it flow from garage to house. The walls will be faced with field stones to make it look original from the ouside, just as the original 1845 house foundation looks.

Did some calculating today and it looks like around 1150 block to do the garage & entry way. It will mostlikely be 5 courses around 2 courses above grade.

Footers will take around 8 yards of concrete and 900' of 1/2" rebar done the way suggested above w/ 3 horizontal strands and crosses at 16" and L shaped pieces to tie the wall to it at alternating 16" spots.

 

[flesburg]

Some years ago I watched a garage being built, and it belonged to a concrete guy, and I thought "that is the way to do it".

He poured 4' walls 8" thick. He ran a lot of vertical rebar, which he had cast into the footer at about 2' intervals. He fastened 2x6 boards to the inside top of
his walls and nailed the vertical rebar to the 2x6s. The walls were poured and when he took the forms apart he had an inside ledge 1 1/2" wide to sit the floor on. He back filled the whole 4' with gravel (mix of fines and course and compacted and watered and compacted. He also compacted outside the walls at the same time. He left a ledge where each door was going to go at below the ledge height. When he prepared to pour the floor he bent over the vertical rebar and tied it into the rebar he used in the floor. 5/8" rebar on 2' centers in both directions, wire tied to the wall rebar and cross wired together at each lap point. The poured floor sits on the ledge on all four sides, and extends to the outside of the walls at the door openings. He said, "the whole unit, footer, walls and floor are all tied together, and I will not ever have a problem. He said he would NEVER fill under a floor with anything other that crushed stone or gravel to the depth of the footer.

I have built two different garages using his ideas, and only have had concrete contractors tell me it was overkill. If I skimp with anything it is not with the footer, walls or floor.

I have had to have two garage floors on attached garages replace in my lifetime, and in neither case was the floor setting on ANYTHING, except fill, and the fill was mostly builder scrap that they tossed in there and covered with a little dirt. I have found lumber, dry wall scrap, drywall buckets and all kinds of junk in the fill under garage floors. I guess it is a lot cheaper for the contractor that hiring a dumpster, and how will the owner ever know what is under the concrete?

Wise men build their garages on a "rock".....

Just my 2 cents worth.

 

[NWOhioChevyGuy]

I like the shelf idea, however My walls will come up above the floor by around 16"-20".

Leaning towards something I can do myself which pushes me towards block (with help from buddies) or ICF's.

 

[flesburg]

You can still do it. Use 12" block up to about 5" below floor height. Every 2' or so bring rebar up through the voids and fill with cement. On top of the 12" block, flush with the outside, lay 8" block. bring the rebar up on the inside of the 8" block. You could place another vertical rebar on up into the 8" course(s).
When you pour your floor, bend the vertical rebar at 90 degrees, and tie it to rebar that you use in your floor. The floor will sit on a ledge, and the walls will also be held to the floor on all 4 sides. So the floor will never settle around the edges and the wall will never move because the floor itself is holding the walls vertically. It may be overkill, but mudjacking a floor in 10 years is not cheap either. Make sure you excavate under the floor until the dirt is hard (might even want to get a civil engineering firm to test it and confirm that it meets compaction needs for your area), and fill the entire void with good fill (stone or gravel), and compact the heck out of it. You might spend an extra couple thousand dollars, but in the long run it could save you more than that.

 

[flesburg]

PS: Block is excellent under vertical load, but incredibly weak under side load.
I used to work at a company in MN. We had an "unloaded" block wall (under construction and about 20 feet high at the time) blow down in a wind storm. Once it has a load on it, ie in your case the floor, it is much stronger in side load, but not even close to a poured wall. I have seen poured walls on hilly lots that extended 8' about the ground level, filled on the inside with gravel and then a concrete floor poured on top. There was nothing on the outside for support, and with proper rebar tying the walls, the wall corners and the joint where the walls and floors met, any hairline cracks NEVER opened. It just sat there like a big monolith.

 

[kbs2244]

I have a 40 page Adobe file put out by the NAHB (Nat Assoc Home Builders)
on everything you would ever want to know about "Shallow Foundations."
The link to it no longer seems to work. But this is what it used to be.
Thay may have gone to a "Members Only" type thing.

http://www.nahb.org/publication_details.aspx?publicationID=437&sectionID=155

If you cannot get it on your own, PM me and I will e-mail it to you.

It is your requested '101" course.

(BTW, is there a way I could have attached this file to this message? I know we can do pics, but what about something like this?)

 

[dipper]

My block walls were 8" then stepped to 6" for the last three courses. The inside was backfilled and compacted with earth, then brought up to the "ledge" with stone and continuously compacted until the floor was poured. The floor was poured on top of the ledge. A very clever way to get a nice solid floor. The outside edge is supported fully, all the way down to the footer.

My pour was completed on wednesday and wil have pics soon!

 

[NWOhioChevyGuy]

kbs2244 - why don't you email it to me at my work email [email protected]
I searched for "shallow foundation" on their website and it gave me 199 returns so I'm not going to have the time to read them all.

Thanks
Keith

I do like the step or shelf idea, and the 12 - 8 or the 8 - 6 step will achieve the same result with a block wall. the expense would be minimal to do this up front and I plan on being in this house when they plant me, so I'm going to do things right when I do them.

I knew I would get the information that I needed if I just asked.

Thanks
Keith