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Homes on Steep Slopes?

Matthew Burr

Member
Joined
Apr 22, 2016
Messages
5
Location
San Diego
Has anyone been permitted to construct a home within a steep slope? It is not clear to me if cutting a home into a hillside is acceptable by reading the following code section (1808.7.1 Building Clearance From Ascending Slopes). All diagrams and text lead you to believe the code wants you to construct a home at the top or bottom of the slope (with sufficient clearances) and not within the slope itself. There is an exception for alternate setbacks and clearances subject to approval of the local building official. Just looking around at existing homes in hillside communities, there are so many homes built into the hillside, some with slab on grades cut into the hillside and some raised above the slope on a caisson/ pier foundation system.

Can anyone provide their experience with building on sites with steep slopes? Thanks!

This residential project is in California
 
Most anywhere in the very dry state of California, you will need a geotechnical and possibly geologic investigation and report(s) that outlines the foundation system or alternates for that specific site that also includes the necessary surface & subsurface water control systems with maintenance work described as may be necessary.
 
I've done many over the years. Initially, "it depends". Depends on the previous mentioned items (+) how much do you want to spend for the view.

Where in California, we have slope failures all over?

What is the height and steepness of the slope?

How is site accessed, above or below?

Is site forested or covered with bushes?

Avoid underlying clay, adobe, etc.

Closest seismic faults?

Location of water sources?

Shall I continue?

What is your role to be with the project?
 
The question is really general in nature and not necessarily site specific. Just curious about others experience in permitting a home within the slope and not on top/ bottom of the slope. I am an architect and am interested in purchasing property to build a home for my personal residence. As with anywhere in Southern California (San Diego more specifically), there are plenty of vacant lots for sale on steeply sloped sites. Yes, I would love to take advantage of the views they provide but am aware of the additional costs for the foundation/ structural system, grading, utilities, etc. compared with a flat site. To try and answer your questions I will give a hypothetical scenario:

Where in California, we have slope failures all over? - San Diego

What is the height and steepness of the slope? - 1:1

How is site accessed, above or below? - Above

Is site forested or covered with bushes? - Brush

Avoid underlying clay, adobe, etc. - not known

Closest seismic faults? 10 miles away

Location of water sources? There is no body of water nearby

What is your role to be with the project? Owner/ Architect

Thanks for your help!
 
San Diego area is a little more stable.

Just a personal opinion, no science to back it up.
 
So Matt, you are looking at "downslope sites"

1. Are there higher slopes across the street and above the site that may drain onto the site?

2. would you have to bring utilities to the site or only connect from adjacent utilities?

3. Sewer available?

4. Buildable sites below/downslope from yours?

5. Local height limitations should be investigated.

6. It ultimately depends on the Geology.

7. Lautner's Chemosphere house in the Hollywood Hills had little site impact (single post support); Ray Kappe's home in Santa Monica Canyon has a natural spring but only touches the site with two attachment structures and bridges the slope. Lots of examples out there.
 
Look at the title of Section 1808.7 "Foundations on or adjacent to slopes" The intention is to allow buildings on slopes.

The code allows building to be on steep slopes but you will need a geotechnical report.
 
Thanks all! To ADA Guy:

1. Are there higher slopes across the street and above the site that may drain onto the site? - No

2. would you have to bring utilities to the site or only connect from adjacent utilities? - Utilities are in the street, so no issues there

3. Sewer available? - Yes but in the street above the property, so would have to pump up.

4. Buildable sites below/downslope from yours? - Yes, but accessed from adjacent streets

5. Local height limitations should be investigated- agreed

6. It ultimately depends on the Geology - agreed

7. Lautner's Chemosphere house in the Hollywood Hills had little site impact (single post support); Ray Kappe's home in Santa Monica Canyon has a natural spring but only touches the site with two attachment structures and bridges the slope. Lots of examples out there. - Thanks!
 
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