?'s on building home on steep slope...

[spur]

We are building a home on a steep slope. The pad has been cut and the slope behind where the house will go is about 5'of clay on top of granite. Is this a good combination or can it cause us problems in the future? The back slope is about 20' high at the tallest point and about 80' wide. The house will be about 15' to 20' from this back slope. Any advice or information would be appreciated. Thank you! Lisa

 

[Ginger]

Lisa

As I understand your problem, you have cut out your foundation ledge 20' down into the face of a granite slope. There is now a 20' high slope to the rear of the house, the top 5' of which is clay. If this is correct then there are a couple of things to check:-

Firstly, does the interface between the clay and the granite dip towards or away from the house? If it is towards the house then you need to get an engineering check done for a sliding failure of the clay over the granite.

Secondly, you need to cut back the face of the clay to a safe angle of repose. Depending on the sensitivity of the clay to change in moisture content, this will generally need to be between 20 to 35 degrees from the horizontal.

Thirdly, to enhance its stability I suggest you plant the clay face you have exposed with vegetation which will soak up excess moisture and bind the face together.

hope this is of help.

Best regards [sig]<p>Andy Machon<br><a href=mailto:Andy@machona.freeserve.co.uk>Andy@machona.freeserve.co.uk</a><br><a href= > </a><br> [/sig]

 

[TimC]

Lisa,

Probably the most important part of Mr. Machon,s response is &quot; ...you need to get an engineering check... &quot;. If you have a condition that you are not completely comfortable with, now is the time to determine if it is safe or not. It will be worth the few hundred dollars to get a preliminary assessment from a local geotechnical engineer who knows the region, the behaviour of the local soils and the effects of the climate. Building on a steep hillside -- anywhere -- can cause problems that might not manifest themselves for several years. So, trust your intuition and contact a local professional -- or at least the local building department.
-Tim-