Advice on Foundation Excavation

[JoelD]

Hi all,

I need to excavate a foundation for a modular home. Will be 4 foot frost wall, going down 4 foot, with footing and then foundation wall up to 2 or so feet above grade, center will not be dug as will be a crawl space filled with crushed stone (maybe poor, not sure).

There are a number of large trees which will need to come out (maybe 5-10, with a bunch of smaller ones).

The house will be somewhere around 28x44 or so.

I expect to hit some large stones, but hope not to hit ledge, if so, then I've got a seperate set of problems, there are other homes in the area, and I see no indication they've run into any trouble.

I have a 7.5 foot hoe on my tractor.

I'm sorting out wether to hire an excavation company, rent an excavator (done twice in the past and made quick work of treeing my home property) or use my backhoe.

Looking for some advice from those who've experienced in the past.

I am working hard to get this thing done on a very tight budget.

I promise to post progress pictures if that helps spur some respones

While I'm at it, does anyone have any thoughts on what:
Excavation
Forming
Pouring

Would cost?

Also, likelihood of finding a foundation guy who would work with me as far as providing guidance on exactly where trenches need to be, how deep, how wide, so if I rented an excavator or used my backhoe, all would be dug how he needed.

Location, southern coast of Maine (York). I have no problem with the excavator company leaving the trees on the site as I can buck and split for firewood, stumps would have to go. The wood is all hardwood.

Thanks all,
Sincerely,
Joel

 

[dave1949]

Hi all,

I need to excavate a foundation for a modular home. Will be 4 foot frost wall, going down 4 foot, with footing and then foundation wall up to 2 or so feet above grade, center will not be dug as will be a crawl space filled with crushed stone (maybe poor, not sure).

There are a number of large trees which will need to come out (maybe 5-10, with a bunch of smaller ones).

The house will be somewhere around 28x44 or so.

I expect to hit some large stones, but hope not to hit ledge, if so, then I've got a seperate set of problems, there are other homes in the area, and I see no indication they've run into any trouble.

I have a 7.5 foot hoe on my tractor.

I'm sorting out wether to hire an excavation company, rent an excavator (done twice in the past and made quick work of treeing my home property) or use my backhoe.

Looking for some advice from those who've experienced in the past.

I am working hard to get this thing done on a very tight budget.

I promise to post progress pictures if that helps spur some respones

While I'm at it, does anyone have any thoughts on what:
Excavation
Forming
Pouring

Would cost?

Also, likelihood of finding a foundation guy who would work with me as far as providing guidance on exactly where trenches need to be, how deep, how wide, so if I rented an excavator or used my backhoe, all would be dug how he needed.

Location, southern coast of Maine (York). I have no problem with the excavator company leaving the trees on the site as I can buck and split for firewood, stumps would have to go. The wood is all hardwood.

Thanks all,
Sincerely,
Joel

You will probably get more answers if you ask a moderator to move this thread to 'Projects'.

I think a foundation/concrete guy would work with you, why not?

Basically, you layout the outside edges of your foundation. For a 28' wide house, the outside edges of the frost wall concrete should be 28' wide. I would check with the mod home builder and verify if they have a required foundation dimension though, they probably do.

You need room in the footer trench outside the foundation dimensions. A typical footer is 16" wide and 8" thick, the 8" wide frost wall is centered on that. So, your trench needs 4" outside the 28' (for example) for the footer (16"-8" = 8", 4" inches each side).

Then, you need room in the trench for a 4" footer drain tile. Usually slotted plastic. I like the type with a 'sock', it comes in 250' rolls from the lumber yard. This is layed beside the outside edge of the footer on a bed of washed stone about 4" deep and a minimum of 18" wide, then covered with more washed stone. The total depth of stone should be a minimum of 18", then covered with filter fabric before backfilling with a good draining sand.

A 16" footer plus 18" of drain space = 34" total trench width minimum.

You also need to clean all the topsoil and roots out of what will be the crawl space area. You need some room to crawl around in there, so it should be dug out anyways. I would aim at a finished clearance of at least 2'-6" from ground to bottom of floor joists, 3' would be even better. The crawl space needs a good plastic vapor barrier on the ground.

You also need a trench to take the drainage away from your foundation drains. If you have a slope to work with, it is always best to run that trench to 'daylight'. Put a non-slotted 4" pipe in that trench and connect your foundation perimeter slotted tile to it. They usually use the green PVC rigid pipe which comes in 20' lengths for this, I forget the schedule number. Get some hardware cloth and a big hose clamp and make a screen to put on the outlet of this pipe to keep critters out.

Assuming you don't hit any big rocks, I think you can do it with your backhoe. If you run into ledge, it depends on how deep and where it is, you might just end up pouring concrete over it if it is solid.
Dave.

 

[Egon]

Addendum to previous poster:

Dig out your stumps and roots. Then remove all the topsoil and level the area. Figure out where the spill piles go and how you will get granular material in for drainage. Figure out the water, sewer and electrical locations and do the necessary trenching and laying of pipes.

By all means, check with the builder on the specifications and what they require for the move on.

 

[dave1949]

Addendum to previous poster:

Dig out your stumps and roots. Then remove all the topsoil and level the area. Figure out where the spill piles go and how you will get granular material in for drainage. Figure out the water, sewer and electrical locations and do the necessary trenching and laying of pipes.

By all means, check with the builder on the specifications and what they require for the move on.

Good Egon.

I didn't say anything about general site prep, but you need a plan as Egon said. Also think about how the concrete trucks will get to the foundation on all sides.

I also didn't mention leveling The rotating laser builder's levels are not too expensive and allow you to work alone easily.
Dave.

 

[JoelD]

Thank you guys

I've understood all posted

My primary residence has perimeter drain going to daylight

The lot in York will not permit that to happen

I was thinking a perimeter drain would not be needed as there would be crawl space but on second thought I'm guessing the idea is for the perimeter drains to get the water away from undermining the footings

How do you do a perimeter drain when you can't get to daylight?

Thanks for the quick responses

I want to be sure I understand what I'm getting into

I think trick will be handful of large trees and stumps I need to pull out I'm going to take a closer look today to see just how big they are size of trees may drive requirement to rent excavator maybe not needed for that long

Thank you
Joel

 

[Egon]

How do you do a perimeter drain when you can't get to daylight?

Might have to use a sump pump.

 

[JoelD]

Might have to use a sump pump.

The crawl space will be vented to the elements therefore the water if any would just flow out if it got to ground level

The crawlspace would have 3-4 feet of fill inside bringing the crawlspace to about ground level

Would I need to go down to footings for sump pump

I know I'm missing something

Thanks
Joel

 

[Rustyiron]

Thank you guys
The lot in York will not permit that to happen.
How do you do a perimeter drain when you can't get to daylight?
Thank you
Joel

Get it to daylight after your last inspection.:thumbsup: Or hide it in a "french drain" a big hole filled with rocks. Sometimes you really wonder about some of the bldg regs.? Have they ever built a house? :confused2:
You might think about renting an excav. for your frost walls, most foundation guys would like a few feet on either side of the wall for working space, that can add up to a decent sized excavation and a lot of spoil that might be hard to "throw" far enough out of the way with your BH.

 

[SixHoeBob]

The cheapest solution would be hire a 953 to dig you a shallow basement to the depth of the bottom of your footer. Stake out the excavation 34 x 50 and have the bottom of the excavation be close to 32x 48. Strip the topsoil, dig the hole, spread fill to the rough grade, put in the driveway. Use 10' lengths of thin wall PVC for footer drains. The roll pipe doesn't like to lay straight. Put a sump pit inside the foundation and connect outside drain to it. Fill inside of foundation with stones to top of footer. Pour 4'' slab.

The 953 can do a much better job in a day, than your tractor can do in a month.
Plus you will not kill your tractor. Once the dirt is loose you can kill your tractor backfilling, and trenching utilities.

 

[Bigturk]

You might want to consider using ICF or insulated concrete forms for your frost wall. They are a super easy system to work with and ideal for a DIY project like yours. Basically foam blocks that are stacked like Lego on a wider footer arond your foundation. They are reinforced with vertical and horizontal rebar and filled with concrete. The concrete will have to be pumped in and that adds to the cost. I build a 32 x 32 house with this system and am very happy with the finished project. I used the ICF from footer to rafters with a full basement. I have plans to build a 24 x 30 garage this summer and will be using ICF for the frost wall. I have a backhoe on my tractor and will be digging the hole myself. I plan to remove all the topsoil from inside the footprint + 2 feet in all dimensions, then dig my trench for the footer around the perimeter. Remember that the footer should be on undisturbed soil so dig slow. If you go too deep it should be backfilled and vibrated. A 24 inch ditching bucket would work good or weld a flat bar across your bucket teeth to get a smooth bottom. Set up some batter boards outside your digging area to help you square you footer and frost wall. Remember to measure diagonally from corner to corner to square your footer. I think it's a good project for you and your tractor. Good luck.

 

[Egon]

Quote:
How do you do a perimeter drain when you can't get to daylight?
Might have to use a sump pump.

Sorry about the confusion. I meant place the pump in a well outside the walls just below the footer depth or frost depth.

 

[dave1949]

Thank you guys

I've understood all posted

My primary residence has perimeter drain going to daylight

The lot in York will not permit that to happen

I was thinking a perimeter drain would not be needed as there would be crawl space but on second thought I'm guessing the idea is for the perimeter drains to get the water away from undermining the footings

How do you do a perimeter drain when you can't get to daylight?

Joel

I would site the foundation elevation such that you create a 1/2" per foot surface slope away from the house in all directions for at least 30 feet.

30' X .5"/ft = 15" So, if you are starting with a level site, where the frost wall emerges from the soil is 15" above the site grade. The bottom of the footer needs to end up 4' below that level, or (48"-15" = 33" below site grade level.)

Since the footer is 8" thick, a standard 4' high frost wall would have 23" exposed above grade. Your bottom row of siding laps over that by about an inch, so from siding to dirt would be 22". (8" footer + 48" wall) = 56" - 33" below site grade level = 23". Hope my math is right 23" is three steps up with a 7" stair riser height.

A daylight drain should be run with a 1/8" to 1/4" per foot slope. You are looking for some place that is 33" lower than the bottom of your footer. At 1/4" per foot, it takes 132' to drop 33". (33"/.25")

If you can't find that on the lot, I guess my next choice would be to run your drain pipe out 50" or so in the lowest direction and let it run into a pit full of rocks lined and covered with a couple layers of filter fabric before backfilling.

I would definitely put in foundation drains. You want the crawl space as dry as possible. Sump pumps are okay but not maintenance free and you have to pump the water somewhere.

It could be you put in drains and hardly any water ever comes out of them, it depends on the water table and surface drainage. If you avoid gutters, as all Mainer's should , your roof will be draining into the ground next to your foundation anyways. You will not have a problem with that if you have good foundation drains.
Dave.

 

[dave1949]

The cheapest solution would be hire a 953 to dig you a shallow basement to the depth of the bottom of your footer. Stake out the excavation 34 x 50 and have the bottom of the excavation be close to 32x 48. Strip the topsoil, dig the hole, spread fill to the rough grade, put in the driveway. Use 10' lengths of thin wall PVC for footer drains. The roll pipe doesn't like to lay straight. Put a sump pit inside the foundation and connect outside drain to it. Fill inside of foundation with stones to top of footer. Pour 4'' slab.

The 953 can do a much better job in a day, than your tractor can do in a month.
Plus you will not kill your tractor. Once the dirt is loose you can kill your tractor backfilling, and trenching utilities.

That works too

The drawback to slabs in that area ( I used to live in Wells, two towns up the coast) is back in the 80's people were slopping in slabs that didn't hold up. They gave slabs a bad name. The real estate market is not kind to them. Most people prefer a basement around there.
Dave.

 

[SixHoeBob]

That works too

The drawback to slabs in that area ( I used to live in Wells, two towns up the coast) is back in the 80's people were slopping in slabs that didn't hold up. They gave slabs a bad name. The real estate market is not kind to them. Most people prefer a basement around there.
Dave.

What I meant was; Dig a hole, pour footers, build frost wall on footers, pour slab inside wall on top of footers. A crawl space without a concrete floor is a lifetime of agony. The floor helps keep the wall from pushing, and makes working in the crawl space bearable. Better yet is to have the crawl space walls 96" high. :thumbsup:

 

[2manyrocks]

If this home is arriving in two sections, you also need to be thinking about an interior section of foundation--either one wide enough to support both sections in the middle or two smaller ones unless the set up crew is good enough to set both sections and join them together "just right."

There are a lot of dirt crawl spaces out there. If you don't have your drainage right, however, down the road you may be blaming yourself saying, "why didn't I....."

Your best/easiest/least costly opportunity to get it right is now before you put a house on it. Corrective action later can be a pain.

 

[JoelD]

Thanks all!!

All posts are helpful, Dave thanks for keeping it super simple for me.

Also, I saw the insulated concrete forms for the firs time yesterday, yes they look very easy.

So I guess you'd form up the footer in a typical manner with 2x8's (google told me the 8 inches I guess code will determine), on undisturbed soil if at all possible. Pour, vibrate air out? then level off and let dry. Then stack up the insulated forms and then fill them with concrete? When you say pumped, does that mean it can't be poured into the forms?

The lot is 80 by 100, from the high point in the lot, to the low point in the lot is maybe 12 inches or so in slope. The longest run from foundation to lot line would be about may 30-40 feet.

I don't think there is anyway I can get to daylight from the footer. Sounds like a rock pit maybe the only option?

Another good point by more than one on the excess soil, a good thing is the road is private and is full of holes, could use some fill for that, likely to have excess fill.

Joel

 

[JoelD]

If this home is arriving in two sections, you also need to be thinking about an interior section of foundation--either one wide enough to support both sections in the middle or two smaller ones unless the set up crew is good enough to set both sections and join them together "just right."

There are a lot of dirt crawl spaces out there. If you don't have your drainage right, however, down the road you may be blaming yourself saying, "why didn't I....."

Your best/easiest/least costly opportunity to get it right is now before you put a house on it. Corrective action later can be a pain.

Good point on the center, I'd not thought of that. Typically how is that done? A piling of sorts?

Joel

 

[Egon]

Then stack up the insulated forms and then fill them with concrete? When you say pumped, does that mean it can't be poured into the forms?[/QUOTE

Using a concrete pump makes it easy to place the cement truck and reach the forms to be filled.

Will you be using rebar and have the walls tied into the footer?

For center support check with the modular supplier.

 

[Bigturk]

Also, I saw the insulated concrete forms for the firs time yesterday, yes they look very easy.

So I guess you'd form up the footer in a typical manner with 2x8's (google told me the 8 inches I guess code will determine), on undisturbed soil if at all possible. Pour, vibrate air out? then level off and let dry. Then stack up the insulated forms and then fill them with concrete? When you say pumped, does that mean it can't be poured into the forms.


A footer for ICF is a little wider than a typical frost wall. The ICF that I used was a total of 12 inches wide, with a concrete core of 6 inches and almost 3 inches of foam on each side. I poured footers 20 inches wide and used a 2x10 for thickness. Place vertical rebar every 2 feet or so, into the footer to tie the wall pour to the footer. A pumper truck cost me $450 extra but made the pour easy. The concrete mix for ICF is thinner and yes it can be poured directly into the ICF from the delivery truck. You need to be able to get to all sides of the pour. Get the footer as close to level and square as possible as this makes the ICF installation easier. Many contractors in my area are using ICF for additions and frost walls. Anyone with good DIY skills can work with ICF using basic tools. The added benefit to the ICF is that your frost wall is insulated, helping keep your floors warm.

 

[2manyrocks]

Good point on the center, I'd not thought of that. Typically how is that done? A piling of sorts?

Joel

Some folks pour a very wide continuous footer and also make their perimeter footers wide on the theory that whoever is placing the home may need a big "target" to hit. Some installers are good--others couldn't set a home on an airport runway.

This kind of shows the differences in regional practice. In middle TN, they'd pour footers, move the home on the site, and then block up to the home.