# rough estimate of foundation on slope



## billv (Jul 19, 2010)

I will be building a home on a slope and am trying to find out a rough estimate of the cost of the foundation. I plan to put timber frame house on the lot but have not designed the house yet and I'll need to supply the foundation up to the first floor. I'm trying to get a handle on the cost of supplying the part up to the first floor. I know I'll also need excavation and probably a pumper due to limited access.

The lot is sloping at about 30% and has shallow soil, from solid rock at the top to about 2 feet soil at the maximum. What I'm looking for is the cost of something like this - rectangle 60 feet x 35 feet. The slope is fairly constant and I assume the highest elevation the foundation would be 2 feet above the bare rock. On the other side of the 60 foot the lot slopes down about 17 feet so the floor top would be 19 feet above this ground level.

Obviously I'm not going to do this with all concrete, but would need to step the foundation down the hill and build up to the first floor with wood. There would be a partial basement and I'd like a slab.

This is obviously not DIY.

Is this possible? Am I crazy to try this? The area would be near Asheville and would be in a more rural area in the mountains (closest concrete is 7 miles from the lot) What about Superior wall system in this situation? Other advice?

Thanks, Billv


----------



## Troglodyte (May 4, 2010)

Is the 60' dimension going down the slope or is the 35' dimension going down the slope?

Also what type of 'rock' is it? Do you know if it can be easily excavated?

Finally how sure are you about the 30% slope? For most wheeled heavy equipment that is the maximum operable grade, meaning very likely that a dozer would have to create a lesser sloped grade around the property, which adds significant cost.

That being said, homes on steep slopes are done all the time. They are much less costly if a basement is incorporated but that requires your rock to be 'easily' rippable with heavy machinery.


----------



## billv (Jul 19, 2010)

Troglodyte said:


> Is the 60' dimension going down the slope or is the 35' dimension going down the slope?
> 
> Also what type of 'rock' is it? Do you know if it can be easily excavated?
> 
> ...


The 60' is down slope. I did talk to an excavator at the site and he didn't seem concerned about the slope for excavation.

I'm not sure about the type of rock. May be graywacke or a metamorphic shale. There is weathered gneiss further down the hill but no here. Where the rock is exposed it's quite hard. In the pits that were dug for the septic permit, it breaks up some into thin 1/2 layers. I don't anticipate a full basement the full 60 feet but a 1/2 or 2/3 basement is desired and an obvious thing to do.

There are homes in the same subdivision that have been built on steeper lots than this. I know one can build on anything, including a sheer cliff. The question is how much is going to cost.

The reason I'm asking is that I'm trying to figure out how much money I need to set aside and if I have enough. I'd like to retire in November but if I'm short I might have to work longer and frankly I'm tired of the daily grind. Thanks


----------



## Troglodyte (May 4, 2010)

Your rock does sound like it is rippable, so it shouldn't be terrible. If you had an excavator on site why was he not able to provide an estimate of the cost?

At any rate, I would say your not crazy. Fairly easily done, I'd suggest step slabbed sections so the first ~30' is a single floor on slab, then the last 30' is two stories on a lower slab.


----------



## billv (Jul 19, 2010)

Troglodyte said:


> Your rock does sound like it is rippable, so it shouldn't be terrible. If you had an excavator on site why was he not able to provide an estimate of the cost?
> 
> At any rate, I would say your not crazy. Fairly easily done, I'd suggest step slabbed sections so the first ~30' is a single floor on slab, then the last 30' is two stories on a lower slab.


Actually he did - 60-70K for the rough driveway, excavation and foundation. I'm not sure if he was including the septic system installation and what kind of foundation he was thinking of or if it was just the foundation wall. As you said I'd like need a stepped foundation with framing up to the first floor as a 20 foot high concrete wall is not going to be cheap. I'm not sure if he was including that framing or not. I'm asking him now.

Another GC estimated a that the foundation up to the first floor would be no more than 100K but I'm also not sure what he was including in that either. I don't think he was including the excavation or rough driveway.

So can see I'm getting some rather wide numbers and not completely sure what I'm getting. Comparing apples to oranges.

These GC's really dont' like to give out numbers. I understand that it could be off but I'm looking for order of magnitude, not down to the penny.

Thanks,


----------



## sherv (Aug 19, 2015)

Hey Bill, 

Did you ever find out if the 60-70K included the septic system and framing?


----------



## billv (Jul 19, 2010)

sherv said:


> Hey Bill,
> 
> Did you ever find out if the 60-70K included the septic system and framing?


Now that house is built, I have those numbers. The house turned out to be 40' downhill and 32' wide with a 24x24 garage. In this area I had to have a geotechnical evaluation done to get the building permit and that included tests of the soil and recommendation for foundation. The main reason for this is to prevent houses from sliding down hill. I wound up with a stepped concrete foundation up to the first floor in some areas, framing in the rest. The garage was concrete up to a suspended concrete floor. The clearing, initial grading, rough driveway, etc and came to around 15K. The foundation was a package that include all engineering, materials and labor and came to just under 60K for both house and garage. Framing up to the first floor, including a 2/3 basement was about 10K. The septic came to about 6K and included the tank and drain field. As I said 2/3 of the area under the first floor is a basement and is actually build above ground level. The 1/3 of the rest of the area below 1st floor and under the basement is a conditioned crawl space (actually high enough in some areas to stand). The conditioned crawl space is sealed to the ground with 10 mil poly and exchanges air with the rest of the house. This prevents moisture build up and mold.

A couple of photos: 

This view is across the garage foundation. The house foundation can be seen behind this and extends to near the wood pile in the distance. The wide angle lens used here distorts the slope - it's actually steeper than this.










This is the finished product. Quite happy with the results.


----------



## tstex (Nov 14, 2014)

Bill,

nice looking stead....I really like the wood arches integrated btw your door and roof gables. 

In your first pic [slope], is there water to the left? Maybe a lake or pond? If so, do you have a view from our house?

Enjoy retirement - I still have two colleges and two weddings, and I know it's going to cost more than a slab downhill..do you want to trade ?


----------



## billv (Jul 19, 2010)

tstex said:


> Bill,
> 
> nice looking stead....I really like the wood arches integrated btw your door and roof gables.
> 
> ...


Thanks. It's fun living here. There's no water. I'm about a 1000' above the valley below. You're seeing what makes the "blue" in Blue Ridge Mountains. In the summer the tree leaves block most of the view, but the winter is nice.


----------



## Msradell (Sep 1, 2011)

Nice-looking place, I'm sure you will enjoy it for a long time!


----------



## jhiggins (Apr 18, 2017)

Billv,
I think I read that you built this house near Asheville NC. If so, could you tell me who you used for you foundation package?


----------



## Canarywood1 (May 5, 2012)

You do know this thread is from August of 2015 right??


----------

