On Mon, 1 Apr 1996, sfarrokh wrote:
Dear Tony,
I enjoyed my visist to your page and was wondering if you have the time to answer a few questions for me. I'd like to build a stone retaining wall in the back of my house. I have a hill in the back which slopes down to about 8 feet from the house. I plan to dig into the side of this hill about 10 feet (half way to the crest of it), in a bow shape. The mouth of the bow would be about 20 feet wide. The hight of the farthest point (from the house) would end up being about 4-5 feet high and at the two ends of the bow, the height would be about 2 feet. My goal is to make the retaining wall look natural and keep the cost down, naturally!
With that said, here are my questions.
1) What kind of base do I need, if any, for the wall? Is it okay to just start laying stones on the ground or a concrete or gravel base is needed? should I worry about frost heave?
This depends if you want a solid wall (mortar) or dry stacked wall. A "wet layed" mortar wall must be on a solid footer (poured concrete). It must extend below the frost line at the least. You should dig down till solid clay is reached.
Dry stacked walls can be laid on stone footers of about the same depth.
Footers should be twice the width of the wall.
2) What thickness is appropriate?
For a 4ft high wall, I'd start the base of the wall about 2 ft thick and finish at about 14" at the top. The front of the wall should tilt back about 1" for every 1' in height.
3) Assuming I use irregular shaped stones and use mortar between them, how much material would I need?
This depends if you can get the stone for free. The best way ofcourse :) A solid stone wall about 18" thick requires about 1 ton per 10 sq ft of wall. If I have the correct view of what you want to do, it looks like 10 ton may do the job. Height 4ft avg X 20ft wide = 80 sq ft. Plus 2 ton for better picking and waste. (backfill)
4) What are the techniques for filling in between the stones with mortar?
This just depends on how you want it to look. Spend a little time checking on stonework in your area and see what goes best.
If you need to buy the stone, it may be best to build the wall out of block and only veneer with 4" to 6" of stone. You may be able to get by with 2 to 3 ton of stone.
5) And what options do I have for the top (the last row) of the wall and how is done?
Save the flat stones for this. A slight crown so the water runs off. Make the morter joints flush with the stones.
6) And finally, do you know any reference matrial I can look up which would be helpful to some one with near zero knowledge of this kind of work? Any hints, pointers, or help you can give me would be greatly appreciated.
There's a few pages right here that you can run a search for books.
Drainage to allow any water pressure to be relieved from the back of the wall is very important. Weep Holes.
Plan well first. Saves big problems later.
Tony