Being the Cottage on the Edge, we have some steep issues to deal with...
On the lakeside of the cottage the grade drops very rapidly. Over the summer the rain demonstrated that there will be a erosion problem. I was concerned that waiting to deal with the erosion issues until next year would be a big mistake when the spring run-off comes. So we decided that it had to be fixed ASAP.
The way to fix the problem is to install a retaining wall or a few... to shore up the slope.
The issue was how to do that when there is still a lot of work in the Cottage? When my eldest son is a landscaper -- and he agreed to take on the task -- allowing me to continue working on the Cottage plumbing and insulation.
Last week end, he and my youngest son started the work. Here is a few tips he has learned to ensure a solid retaining wall:
1) Maximum of 7 courses of retaining wall material
Seven courses of retaining wall material, we used 4" x 4" pressure treated posts, will give about 2.5 feet of retaining wall. Any higher and the pressures of the soil behind tend to push the wall. Egin, my son, says going to 9 might be ok.
I was ready to order him 16 foot lentghs of the PT posts, however, he insisted on 10-foot lengths. Through experience he found that he never uses anything much longer even when the wall itself is much longer as he ends up cutting the posts to insert the tie backs anyway.
Each course is nailed to the one below it with 8-inch galvanized spikes.
2) Install drainage
Another trick to reducing the hydrostatic pressure against the retaining wall is to provide a means for the water to drain away easily. He always places weeping tile at the foot of his retaining walls. It also helps in avoiding washouts in the spring and in heavy rainfall.
3) Install bracing
The picture illustrates the construction of tie-back bracing for the wall. This ties the retaining wall right into the soil behind it. The weight of the soil itself holds back the weight against the wall. It is a simple 'T' structure, with the 'T' about 6 feet in the soil.
4) Anchor the bottom course
Another trick is to tie the bottom course into the soil below it by driving 1/2-inch rebar thought the post and into the soil. Egin uses 4-foot lengths of rebar, driven in every 4-feet.
5) Keep it level
Not only is it more aesthetically pleasing but the pressures along the retaining wall will be equalized.
Egin will be completing this retaining wall over the upcoming weekend, but will also over the course of the fall and next spring be installing more landscaping options. We will post our observation on all of them.