HVAC Erosion Control With Timber Retaining Wall & Downspout Drainage System in Potomac, MD
Share this project:
Scope of Work
Project Overview
The ground along the side of the house was washing out, and it was happening right under the air conditioning condensers. The slope next to the stone steps had eroded down to bare dirt and clay, which left the base under the units unstable. This allowed water to run toward the house instead of away from it.
We rebuilt the base under both condensers, added a tiered timber retaining wall to hold the slope in place, buried the gutter downspout to carry roof runoff down the hill, and regraded the area so water drains away from the foundation. The air conditioning units now sit on a level, solid support, and the side yard is set up to handle runoff instead of losing soil every time it rains.
Before / AFTER
Site Conditions
The Property and Site Conditions
The work area was a narrow side yard slope running alongside the stone steps and the gray house siding. The slope had eroded badly, leaving gaps under the condenser pads and an uneven, shifting base. Two air conditioning units sit in this area, so both needed a stable footing.
Since the slope fed runoff toward the house, water pooling was an ongoing problem. The gutter downspout made it worse by dumping roof water straight onto the slope. Any fix had to do three things at once: hold the hillside back, get the roof runoff under control, and move the rest of the water away from the foundation. The existing stone steps and the layout of the side yard set the boundaries we had to work within, so the retaining wall and grading had to fit the space rather than reshape it.
In Progress
ASSESsMENT
What We Did
Rebuilt the Failing Base
First we dealt with the failing base. We added a clean fill mix under and around the condenser area and compacted it in layers to close the gaps and settle the uneven ground. Building it up in compacted layers matters here because it packs the base evenly instead of leaving soft spots that settle again later.
Built the Tiered Timber Retaining Wall
Next we built the retaining wall using pressure-treated 8×8 timbers laid horizontally. We set it up as a multi-tiered, low platform with a mid-slope terrace, which breaks the hillside into steps instead of one steep face that wants to slide. Each row of timber was locked into the hillside with heavy-duty spikes so the wall stays put under the weight of the soil behind it.
Buried the Downspout Line
We also buried the downspout to get roof runoff out of the picture. The gutter downspout was dumping straight onto the slope, so we hand-trenched a line at 10 to 14 inches deep, laid in 4 inch perforated corrugated pipe wrapped in filter fabric and drainage gravel, and connected it to the existing downspout.
The pipe daylights farther down the slope with a splash block so the water comes out where we want it. Burying it under the new grading means heavy roof runoff bypasses the soil and the HVAC pad entirely instead of washing out the hillside during the next big storm.
Regraded the Slope for Drainage
Last, we regraded around the units and the slope to pitch surface water away from the house. The grading and the buried downspout work together: the pipe handles the concentrated roof runoff, and the grading moves the rest, which keeps water from pooling against the foundation or eroding the soil we just stabilized. We finished the beds with dark gravel for a clean, low-maintenance surface around both condensers.
Completed Project
Thinking About a Similar Project?
If you’ve got a slope losing soil, equipment sitting on a shaky base, or water running the wrong way toward your house, we can help you sort out what’s going on and put a fix in place that lasts.
Free Project Planning
"*" indicates required fields