I own a old home on a hilside with a full perimiter foundation. There has been some excavation and leveling of the ground belew the house and there is also a small in-law unit and utilities for the house down there. I would like to improve this area with retaining walls and gravel. Most of the area is dry year round so not much moisture to worry about.
My question is this, Can i build these walls out of wood, or do they need to be made from concrete or cinder block? I am afraid that any type of earth to wood contact, even if it is not contacting the house, might still attract termites.
Replies
If the wood look is fine with you, check out the plastic 'railroad ties'. They're basically plastic logs made out of recycled plastic. You can find them in use at a lot of playgrounds these days.
Plenty of wood retaining walls out there. A common way to do it is to sink 6x6 posts into concrete and then use 2x10s horizontally for the 'wall'. The 2x10s are laid in on the uphill side of the 6x6s and bolted into place. All of this would be pressure treated material. Lifetime not as long as concrete, obviously, but easier to do and maybe more the look you want. It's a good idea to have drain rock against the back of the wall instead of soil--keeps less moisture against the wood.
thanks for the reply. i know how to build, and have built, many wooden retaining walls outside. my question is whether it is acceptable to use wood underneath a house. i am concerned with attracting pests.
thanks, kirk
Plastic and pressure treated will not attract pests.
Sorry, I did not get the part about 'below' the house--I assumed you meant on a slope outside of and downhill from the house. My bad.
I've seen plenty of wood retaining under houses. Yeah, I prefer concrete but it's a lot more trouble and money, and if you can keep the wood dry and use PT in the first place, it will work fine. If the crawl space is damp I wouldn't do it.
"might attract termites."
1) Move to Alaska - no termites.
"Can i build these walls? "
2) Check with your building department. Often there is a height (2 to 4 feet) above which retaining walls must be engineered.
Properly done, concrete wood, metal, and plastic are all viable. As are many different designs. Monolithic walls. Large vertical members providing the strength (6x6s, etc). Sloped concrete facing blocks for short heights. Face plates tied deep into the hillside for great heights. Driven sheetpile. Helical Screws. Cast-in-place piles, etc.
So many options, so little dirt.
Driven sheetpile?
Wutizit?
Here's a picture of sheetpile being driven. Sorry about the jumbo URL. The caption for this photo reads:
Sheet pile were driven using a vibratory hammer
pictured here. The vibratory hammer grips each pile
from the top and vibrates it, loosening the soil
beneath, allowing the pile to drop into place.
http://yosemite.epa.gov/r10/cleanup.nsf/9f3c21896330b4898825687b007a0f33/8572edc919ef3f31882569f50002f069/$FILE/001207Wyckoff01.JPG
And here is a closeup picture of the installed sheetpile.
http://members.itol.com/~roensalvage/stonepic2.html
Edited 12/5/2003 9:48:48 PM ET by Uncle Dunc
Dunc has posted pics, but if you're on dial-up, here's goes:
Start with something like corrugated metal roof but 20 times the thickness and 20 times the interval between ridges and valleys. Every few feet, make one end a solid tube. And the other end a sleeve to accept that tube. Get a big piler-driver and slam away. One after another, side by side. You can buy them outright or rent them. Rent is per week or per month but you also have to buy the inches or feet on each end that you bung up.
Used in the big city for skyscaper foundations (during construction) and for dewatering operations during construction below the water table. Some people use them up here as seawalls to prevent erosion.David Thomas Overlooking Cook Inlet in Kenai, Alaska
Thank you gentlemen. Now I know what they call the stuff they have around parts of the harbor here. I will try to act cool and drop that term someday soon.
However, I don't know if we could get that rig under the original poster's home, so I think we're back to the 6x6s or maybe some heavy galv pipe for the verticals!