Soil piled up against a wooden fence, or other structure, can cause it to rot years before its expected lifespan can be reached. This can be expensive and it is never easy replacing a fence once your flower borders are completely planted. This winter I took steps to protect my fences from rot and, all in all, was not too painful an experience – other than my back.
Apply EPDM roofing, a thick rubber based material available at building supply stores, nailing it along the top of the horizontal board, at the top. It should extend below the bottom of the fence boards.
Apply a sheet of galvanized flashing, available by the foot or in rolls, over the EPDM roofing, again nailing near the top. It is best to nail all these no more than to every second vertical fence panel to allow the fence to expand and contract. The flashing will serve to protect the rubber membrane.
Lay construction grade landscape filter cloth in the trench and against the fence in a U shape and fill the trench with 3/4 inch crushed rock – excess cloth towards the flower bed side of the trench should then be folded over the top of the backfilled gravel and additional gravel added to top things up to the soil level of the bed.
You can also partly bury a 2×8 cedar board, on edge, just in front of the gravel trench, nailing it to stakes in the ground; this will stop the gravel and soil from mixing excessively but is optional and more a matter of cosmetics.
Add a strip of cedar lath to cover the flange of the drip flashing and you have an attractive solution that will extend the life of your fence for many years to come. The shiny surface of the galvanized sheet metal and flashing will turn dull in a year or two and blend perfectly with the rest of the fence.