Build a Wood-fired Cob Bath for Free

Suzie Cahn
Tuesday, 16th May 2017

Suzie Cahn from the permaculture smallholding, Carraig Dúlra in Ireland, shares how they built an outdoor bath heated by woodfire, insulated with cob and with a willow screen for privacy.

If you do a web image search for cob baths you might be surprised how many different designs you see. At our permaculture smallholding, Carraig Dúlra, we love upcycling unwanted waste and using natural building materials. We had been donated an old cast iron bath a few years ago and really wanted to make use of it. Around the farm there are a few materials available, bits of wood, bricks, small quantities of things like lime, and sand from other larger projects. We are also occasional skip/dumpster divers, so for this project, we didn’t have to buy in anything.

Our site is up a small hillside in County Wicklow, in the south east of Ireland and we have been developing it for 10 years now. We’ve forest gardens, and annuals, ponds, swales, an amazing greenhouse with cob beds and a big barn/class room. However, none of this would be possible with out a steady stream of volunteers and permaculture course participants. So we thought it was high time we provided some additional luxury to compliment our sauna wash house for these onsite campers.

Carraig is the Irish for Rock and Dúlra means nature, often our designs reflect both. We have plenty of rocks and we decided to incorporate a small 'sally garden' or willow bed in our design to make use of the grey water when we pull out the plug. We wanted the design to reflect good use of permaculture principles especially ‘produce no waste.’

We are hosts to a government employment scheme for long term unemployed people. It is called Tús which means 'start' and giving people a new start is its aim. In the early part of the year when there isn’t much to do in the garden there are less people on the farm. This year it was myself, my husband Mike and 3 Tús workers. We sat around the stove in the barn over our lunches designing a wood fired cob bath. Everyone contributed ideas and we had plenty of time to tweak their practicalities. This meant that when we came to the actual build, it was relatively straight forward. All the Tús men contributed despite having no previous experience, and having a fore-woman/educator.

Justin an unemployed language and European studies graduate with a masters degree, made the project his own and is justly proud of the results. Despite his initial scepticism about anyone actually using the bath, he was the first to test it giving it a thumbs up. He’s looking for the next building project opportunity on the site and considering doing our permaculture design certificate course coming up this June. 

I’ve had a go in the bath too, filling it from our rain water tanks and heating it up while doing some sunday watering - it was ready in a few hours to take the aches out of my back. It was a very relaxing and unique experience, sitting in a warm bath (that isn't cooling as I left the fire slowly burning underneath) while smelling woodsmoke, looking at clouds passing above, listening to the birds and once a small plane! I’ve since added an umbrella to the design just in case one passes next time.

The method that was used can be worked out fairly easily from the photographs but followed this sequence: 

  • propping the bath up high enough to give room for a reasonable sized fire area (we used a combination of some strong metal frames found in a skip and stones with lime mortar)
  • tweak to level the bath (if any slope then it should be towards the plug)
  • make a fire area (ours used stones, old slabs and fire bricks left over from a cob oven build)
  • position the chimney hole so that it is higher than the bottom of the fire to help create good draw 
  • attach the flue 
  • make a door for the fire area to help keep heat directed under the bath (we used one of the metal shelves from that same skip dive)
  • fill around everything that needs it with cob including the willow bed edge 
  • lime plaster exposed cob
  • lastly add steps and any screening needed 

Suzie Cahn is co-founder Carraig Dúlra She tewwts at:

Upcoming PDC: Located in Wicklow, the county known as the garden of Ireland, the 12 day PDC (UK Permaculture Association Accredited) takes place from 17th to 30th June 2017: 

Carraig Dúlra is a 10 year old permaculture teaching and research focused, community connected, smallholding. It has a diverse teaching team, and styles, with practical elements every day, rated highly by past participants for people care, rich content, nature connection, and accessibility no matter what level of experience participants bring.

Course fee includes all food and camping spots and is on a sliding scale: Standard fee €1000 waged / €1200 good waged / €800 low waged / plus unwaged concessions.

A quick glimpse at a past course:

Useful links

Watch: Cob rocket ovens

How to build a Rocket Stove Hot Tub in The Permaculture Book of DIY

How to build a willow fence