NOTES on. design // Ferns and French drains

Finding elevated levels of damp in my new home has left me chasing multiple ways to prevent moisture rising up my walls. The garden is no longer a sanctuary but it certainly holds some answers.

It all began with a mouldy bag of porridge in the cupboard. Followed by a mouldy box of Yorkshire tea. Followed by mouldy anything that would let the moisture in: paper, cardboard, perforated tea bags. I made a few emergency calls to help rip the offending kitchen cupboards out. Four weeks later and we’re on a fully fledged excavation journey through the walls and floors of my house searching for the causes of an eye-watering amount of damp. Green mould, black mould, rotting joists, soaked bricks, sodden render, you name it, this house – or at least the kitchen and dining area – has got it all.

And so, we’re suddenly knee deep in a 3-month long renovation project that involves damp proofing the parts where the water can get in, or travel through, and making good on the parts I’m having to live without, namely an oven, sink, dishwasher and washing machine. I do have a microwave and a fridge – and a camping kitchen set up in what’s left of the garden – so I shouldn’t complain but some days it obviously takes its toll. Leaving the chaos to sleep in a field at Glastonbury was one of my best moves.

Back to garden chat, part of the problem stems from not just unruly pipework and blocked drains outside, but also that the garden is on a slight slope sending water rolling down the patio when a deluge hits. The patio also covers most of the area and has breached the damp proof course around the house. And so the slabs are coming up and a French drain will be installed. I’ll also have to deal with the slope sooner rather than later, which means a small step may be required. A garden of two halves.

I’ve never really thought about garden design in these terms. Rather I’ve viewed it largely through an aesthetic lens. But there’s so much that needs to be discussed around water. Too much of it during a flood or poor drainage, too little during a drought. As well as the French drains, I’ve also been looking into plants that can soften the edges a bit and make best use of any overflow.

For those who haven’t heard of French drains they are essentially underground drainage ditches filled with gravel, smooth stones (my preferred choice, each stone being at least 1cm diameter) or tile and sometimes topped off with soil. I’ll also be including a perforated pipe running the course of each ditch to help direct excess water away. There can still be a watershed effect however and so I need nearby plants that flourish in damp conditions. Ferns are ideal and also suit the shaded area running down my side return. Such plants should make the area more attractive but can also help stabilise the soil, reduce erosion, and absorb excess water.

It’s a bit too soon to work out a full planting plan yet but I can dream along the lines I’m being dealt. This also includes coming up with creative solutions to deal with the general issue of too much patio versus planting space – not great for drainage or for wildlife – plus a north to south downward slope that takes excess rainwater directly down to my kitchen wall (soon to be my kitchen patio doors). No doubt there’s a frost pocket at that point too where freezing water vapour rolls down the ‘hill’ towards the house.

Two options have already sprung to mind – one involving a terraced effect, with a step up to the upper portion of the garden, and planting designed to absorb some of the downward flow. The other is to create a platform directly outside the French doors on which a dining/seating area can be arranged. In either case, the height of the perimeter drain and the damp proof course will dictate what happens next. All a bit overwhelming, but from tricky situations often come exciting solution and so I will press on.