My lawn turns into mud between October and April every year (UK), and then in the summer becomes almost impervious to garden forks. If I do manage to break the surface, it's still fairly damp underneath. The topsoil varies across the garden but is mostly medium to heavy clay, with some more sandy areas and the odd lump of chalk. In winter, it generally remains muddy even after a week or two without rain. It doesn't rain that much here, but it's damp, dark, and drizzly all winter. My goal is to have a garden where I can let my dog out in winter without him traipsing large quantities of mud back into the house.
To see if a soakaway/dry well is an option, I dug a test hole a metre deep and filled it with some water to see if it drains. However, after three days, the water level had not dropped noticeably, suggesting that my subsoil is mostly impermeable. However, in my area, I am allowed to drain the lawn into the storm drains, so that should not be an issue.
I read a lot of reputable sources suggesting online to install a French drain system, by digging trenches of ~45cm deep on a 1:100 fall, with perforated pipe and gravel wrapped in non-woven geo-tex, spaced ~3 metres apart, then covering them with fresh topsoil. To test whether this might work, I excavated some trenches in the muddiest part of the garden, then turned the hose on a metre away to see if the water flows through the soil and into the trench. However, that did not happen - instead, it just formed more mud where the hose was running and the bottom of the trench remained empty and dry.
So now I'm wondering: will a French drain system will even work if I don't fix my topsoil's permeability? What good is a drainage trench if the water can't even percolate through the heavy topsoil to get to it?
My options include:
- Continue digging trenches for French drains and trust that over time, everything will work and the garden will magically become less muddy.
- Install the French drains as above, but also excavate and remove all of the topsoil, grade the clay subsoil so that it directs water to the drains, then replace the topsoil with newly purchased loam.
- Install the French drains as above, but fix the existing topsoil's permeability by rotovating in large quantities of sharp sand, grit, well-rotted manure, and bark.
- Don't even bother with the French drains, just fix my topsoil as above, either by replacing or rotovating with grit and organic matter.
I'm leaning towards 2 or 3, but before doing anything too drastic it would be nice to know if I'm being sensible. For reference, I had a few landscapers around, and they mostly tried to pressure me into artificial grass because the soil here is apparently a nightmare. The best quote I had for fixing the situation and installing a real lawn was £20k (the garden is 20m by 8m), and that involved removing all the topsoil down to a depth of 30cm, adding a layer of gravel and sharp sand, then a new layer of topsoil. That didn't sound like it would fix the underlying problem to me, just delay it, but he said it's worked well for other clients several years on.
Edit: The compaction is caused just by walking on the lawn when it's muddy e.g. to get to the shed or rabbit hutch, but I will be putting a gravel path down instead. Plot is around 130 years old, but the house got hit by a rocket in the war, and the garden contains a lot of the debris from the original house (occasionally UXO is found in nearby gardens when landscaping). I'm not sure if the debris causes any problems, but having walls buried under the soil probably isn't helping.
Sunlight is full sun over summer, but when the sun gets low in the sky over winter, it rarely gets direct sunlight (if it's ever not cloudy anyway).