Question
Hi!

I have a fenced in lawn and the fence encloses most of the lawn except a strip ~90 inches wide by ~20 ft. This strip of lawn is adjacent to the driveway so it's kinda sandwiched between driveway and fence. The fence is made of 4x4s about 4 ft above the ground connected by three horizontal boards.
Now to the meat of my question. I want to build a raised bed 45-50 inches wide for the entire lenght of the fence. I am planning to put a waterproofed mortared stone wall in the front (the side facing the rest of the lawn strip and driveway). What I don't know is how to build the back of this bed, which would be adjacent to the fence. I don't want to lean it up against the fence (rotting) but I don't want to build another stone wall there either. This is not a decorative side, so I just need something practical that would hold the soil in and separate it from the fence.

Thank you very much for your advice.
Alexander

Answer
Hello,

Consider using an EPDM rubber sheet on the face of the fence that will be holding the soil. You will have to seal the top of the sheeting in some way because you will not want water leaking under the sheet. Any water trapped under the sheet will promote rot of the fence boards.  A more rigid plastic material such as plastic roof flashing could also be used.  EDPM rubber is used for roofing. Pool liner material would also be a good choice.  Attach the material with galvanized or stainless steel fasteners and then seal over the heads of the fasteners with a sealant rated for below ground use.  The newer copper treated lumber will not accept aluminum fasteners or sheeting. Applying aluminum will cause galvanic corrosion. The copper will react with the aluminum and cause the aluminum to corrode.  The newer copper treated wood will also corrode any ordinary steel fasteners very quickly.  Aluminum can be used with the old arsenic based pressure treated wood.


A more desirable design would be to have the fence boards perched on a low wall above the soil. Think about shortening the fence boards and perching them on the back wall of your raised bed. The wall would run along the center of the fence posts.  To avoid soil contacting the posts perhaps a concrete collar could be wrapped around the posts.  Good luck. Let me know if I can be of further help.

Mark  Harshman
http://www.mahdrafting.com
Email: [email protected]

http://www.scribd.com/markscrib47