I am interested in building a duplex on a steeply (down-) sloping lot. I’ve read about different techniques to reduce foundation and associated costs (retaining walls etc.) such as using a plan without too many corners, orienting the plan parallel to the slope and steping down levels along the slope. The last two, however seem to be conflicting. If you step down then the profile will be more perpendicular, rather than parallel to the slope?
What are your tips, approaches to building on down sloping sites?
Replies
Piers.
Grade Beams.
And, oh, get a soils study and retain a structural engineer.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
They aren't contradictory. Imagine a ranch house 60' x 40' parallel to the hill. Imagine it having just a half basement 60 x 20. Pick your own numbers. Use a stepped footer. It's what some neighbors do on our mountain. Most do something like that, and then have about 10' to 30' flat behind the house notched into the hill with a retaining wall where the notch is. I went a different way and did a big notch into the mountain and bermed the house to 18'. But there were some special circumstances that allowed that.
In design the first rule is don't mess with mother nature.
Tip number 1
Never design a building on a slope with a recessed section in the front wall. In other words, make the front wall straight. Otherwise picture a cup facing the slope of the hill and water running into it.
Your house is breaking the natural flow of water as it drains downhill, try not to stop it.
Gabe
That's a good point. All the houses here are sited so that the hill above humps right behind the house (what's the right word? it's almost like a cricket behind a chimney) rather than forms a valley. So the water is mostly directed to the side before it could reach the house. But there's _one_ house not like this, and they have to put speed bumps on their drive to try and redirect the water. I remember looking at that house when moving to the area, and not buying it because of the runoff nightmare it appeared to be.