Earth Floor (1 of 2)

humblebee hive – retrofit #10

Yikes, this all unfolded last year and I’ve not posted anything since!

It’s been a toughie, with M working away 3-4 days a week for nearly two years I’ve felt like a single parent half the time (but without the autonomy) to S in their GCSE year and T who seemed to turn full blown teenager/young adult overnight… cue Harry Enfield’s “Kevin turns 13”! (But they still come in for mummy cuddles occasionally, thank goodness! 😊)

And how mad is this… an Earth Floor!!!

Probably my hardest post – and definitely the hardest decision & implementation phase to date… hence the extended procrastination (correction, “thinking/processing time”). And I’m using our slow travel home through Germany – the homeland of Passivhaus – to start to draft this.

Deciding what to do about the existing floor – a pretty typical suspended timber construction – was always going to be the Achilles’ heel of the project, because it’s the most disruptive part, with potentially the lowest “return”, and yet it’s still crucial to achieving overall performance. I say that but the draughts from the ventilated subfloor were decidedly significant after we’d insulated everything else.

The Options

In my mind there were two macro options to choose from, and my brain regularly flitted between the two:

-          Most energy efficient: remove timber and fill the void with an insulated solid floor

-          Least disruptive, more natural material compatible: lift up boards, insulate between the joists with wind tight and airtight membranes while maintaining ventilation below to the joists.

This mental battle epitomises my daily internal debates, brought about by my knowledge of the rigorous application of performance principles as dictated by Passivhaus, and my more innate affinity for earth-friendly practices and connection to more circular and organic ecosystems.

And if I’d started with a fixed budget in mind, we wouldn’t have the homely, tactile, warm, in-our-eyes totally beautiful, finished article we have now.

The case for emotion-driven decision making: the key, finding joy (even if it means pain) -  it’s amazing how your brain seems to wipe out the bad.

Admittedly, in my work (as with this endeavour), my heart sinks when I hear the words “what’s the payback?”. I’ve written about this before: no one ever asks that of their engineered timber or parquet floors, their new mattress, granite worktop, meals out, or even their car – which actively depreciates over time! But saving energy, carbon and providing better health and comfort, with a wow factor to boot… well, surely we considered the economics…

It's fair to say what we spent on our floor makes no sense in that respect – I won’t even do the numbers - but it brings us joy, and it’s a bit “out there”, and it quite literally grounds us. The feel underfoot is something else.

OK, so, how did we get here… We were still deliberating on the options – having given the Retrofit Hub* team a heads up that we were planning to get the work done over the summer - when M spotted and forwarded a tweet by Jeffrey Hart aka The Natural Builder… and that was it! Heart decision there and then.

And to be fair, the “earth floor” part is in fact a finish and so costwise not much different to a high quality timber floor.

What is an Earth Floor?

Or “soil floor” as one of my co-working mates decided to baptise it 😊. So, yes, in essence, compacted soil: you may have heard of “rammed earth” walls, and an earth floor has a similar composition of clay and sand with fibres.

In our particular solution, the “earth” part is only a finish, one that you could bury underfloor heating pipes in if you needed to, like a screed, and it’s laid on a compacted gravel base (MOT Type 1 in our case). If it’s clay rich, it could be from your own site dig, or local construction site excavation, as long as you send Jeffrey a sample for testing.

It’s an alternative buildup to hempcrete, which we had also toyed with as an idea.

The Technical Bit

We ditched the suspended timber floor - grateful to know that L from the retrofit team took the joists to build himself a garden room, because wasting the timber was my main obstacle to going for this solution.

Pictures courtesy of The Retrofit Hub

As an insulator, soil is not massively performing (it has mass, and insulates better than reinforced concrete, much worse than polystyrene for example), which is why we insulate solid ground floor slabs.

So below the earth floor we opted for what could be considered a low impact material: foamglas aggregate (foamed recycled glass aggregate) – it looks (and feels) a bit like the fake coal chunks in a gas fire.

Glapor or Geocel (trade names) is anti-capillary and so won’t transmit moisture from the ground, and doesn’t leach chemicals into the ground. Although it’s nowhere near as insulating as XPS (polystyrene), because we had a 600mm void to fill, we could use a good portion of that as our insulating substrate, 450mm when compacted down.

Pictures courtesy of The Retrofit Hub

The geotextile provides a physical and hygrometric interruption in the layers, and stops the gravel falling into the gaps of the foamglas. It also laps up the perimeter to contain the compacted foamglas.

The earth floor went on rather like a render. We needed a solution for the door thresholds, and temporary timbers were laid so there was something to butt up to. And as we were taking the opportunity of a new ground floor to strip out the kitchen, we later reused and placed some of the sturdy kitchen tiles, set in a classy charcoal grey lime plaster, which I love.

Colour

Speaking of finish, Jeffrey had posted on LinkedIn a selection of colours he’d been playing with and we discussed the hues and shades that might be possible. I was after a pinkish terracotta to reflect the mediterranean feel I’d been aiming for, but not too dark because our ceilings are low and spaces are quite small.

He mocked up a few mixes and sent me photos in different light – it is wonderful how the sun completely transforms it! The final effect is quite a bit darker because of the oils, but somehow it totally works.

Programme, and Family & Friends to the rescue!

Jeffrey did warn us there would be drying periods for each operation including the Linseed and Tung oil application, as well as a final wax and buff. Some of this we expected, and it meant we couldn’t live in the house for a good few weeks, so we planned it to coincide with some family holidays with the bulk of the work, and a stay with patient in-laws to bridge them…

Our lovely friends had us stay a while as the programme went on longer than anticipated and we house sat for another friend as the school autumn term started up again… Having everything we needed for that out of the house in time (we couldn’t walk on the wet floor) was another logistical hurdle, but we borrowed and scrimped to get the kids on their way and it was quite an adventure overall, and we found out how important our friends were to our family - the village that we built around us… bonus!

Finish and care

The earth floor colours a few shades darker with the natural oils. Also be prepared for the smell of the linseed oil to carry on for many months – we didn’t mind this and didn’t notice it after a few weeks, but visitors do, and it registers again walking in after time away…

And just like a timber floor, it needs to be treated with care, as it will dent (after 12 months there are a few of these in the kitchen where I’ve dropped the odd pan lid) and furniture needs soft pads and rubber feet so as not to leave sink marks. The earth team left us “biscuits” – patties of the earth floor with leftover mix – that can be used to patch up divets at some point. They can also use the biscuits to colour match at a later date, should it be needed.

The good news is that it can be damp mopped, swept, vacuumed or steam cleaned. Harsh cleaning chemicals are to be avoided, which totally suits me as I’ve eliminated these from my arsenal – a quick lightweight hoover, microfibre cloths and occasionally water, works for us. Spills should be mopped up quickly – rather like a cork finish which I’d envisaged at some point – and marks need a bit of elbow grease but that’s it.

This is a long post so I’ve decided to split it. More on considerations, challenges and costs, and a write up of my offcut-based and Plykea kitchen (I love it!) in the next article… but it won’t take me a whole year to publish, I promise!

*Have you heard..? The Retrofit Hub have opened a training academy in Trafford (Manchester): check out their courses!