Building my own hot tub (part 1)

January 11, 2010 at 14:53 (DIY - hot tub, Hot tub (part 1))

A hot tub or as we call it in Estonia “kümblustünn” is a thing I have been missing from my yard. Specially when it is -15 degrees out side and it is snowing.
Half a year ago I planed to build one my self, searched for some blueprints and ended up with nothing. Found only some crappy ideas how to build one from 1000l plastic canister, whose ugly looks and small dimensions would scare birds away.
Around 6 months have passed by since I got the idea for getting a hot tub. Now I wanted to build a motor boat, but hey! My wife said I should keep my promises better, she was pointing out the idea of a hot tub in the yard (she wanted to have a nice time in the hot tub with friends and I don’t mind to see bunch of women running in bikinis during wintertime). So I decided to build one and from wood as its done in Northern countries.
Short notice: If you plan to build one yourself following the steps I described or blueprints, please read all the posts about building a hot tube that I will have posted here in this blog before you start.
Ok, First thing is to build a huge barrel from wood. Why wood and which wood? Wood is good thermal isolator and easy to work with. For a hot tub it has other good qualities such as: dry wood expands when getting wet, fir and pine have resin inside which will prolong the life of the hot tub compared to oak or birch, to be mentioned wood is also more natural than than any damned plastic canister. In my opinion, pine would be better for hot tub building than fir, as fir planks usually have more branches, which affects the quality of a hot tub being water tight later on.
After a couple of days of planning and drawing some blueprints it was about time to buy the material (wood).
I have decided to make a hot tub with diameter of 2m and height of 1,1m. It should be enough up to 6 people as I do not intend to install stove inside of hot tub. After some calculations, I ended up with an aprox. need of 130m wood (45×95mm) so there can be remaining pieces. Some remaining pieces of wood can be used for building hot tub furniture (beer can holders and chairs). I got my hands on fir planks with good price and 4 sides sliced (machined) and they were 45mm x 95mm, which comes from standard unsliced 50mm x 100mm wood planks.
So how wood planks should look like? Because machined wood (modern style) was too expensive to buy and pointless to buy equipment to make some for yourself.
I decided to go a bit old school and make it as predecessors use to make wooden barrels.

Modern Style of wood plank allows you to build easily various shapes of hot tubs, for example oval shape or different sizes with out re calculating edge angle for side planks again.
As the outer diameter is 1,95m (why 1,95? you will figure it out later), I had to calculate the length “circle” (6.123m). Now divide outer length with the width of wood plank (its 95mm) 6.123m/0,095m= 0,0645 pcs.
which means that you need almost 65 side panels (wood planks). The count of side planks also gives us possibility to calculate what the angle for side plank edges should be. Circle inner angle amount is 360 degrees so as we have 65 side planks it means we have 65 corners, every corner has angle 5,54 degrees, we need to know the correct angle of one side plank both edges, lets divide 5,54 with 2 and we get= 2,77 . This is the correct angle that every side plank edge should have. When you put two side planks together you should have an angle of 5,54 degrees

The easiest way for cutting the edge of planks is using a panel saw which blade angle is adjustable. I bet you have better conditions than I have, but if you keep working, then -15 does not feel cold at all.
That’s it for now.
Need to have a smoke break.



  1. Owen Lambert said,

    interesting. Im in Australia and I think youve done a great job to inspire me to have a go, right now we are building a Sauna so that job comes first.

  2. badtunnaexpert said,

    Hei Tarmo! Väga lahe et sa sellest kirjutad ja jagad oma kogemusi. Ameeriklaste ja üldse inglaste jaoks tähendab kümblustünn eelkõige jacuzzit, aga me teame, et sel pole tünniga suurt midagi pistmist. Nad kõik peaksid proovima üht tõelist puidust kümblustünni! Selles mõttes on inglased paljust ilma jäänud. Kahjuks. Seda õpetust peaksid lugema paljud! Edu!

  3. said,

    There’s certainly a great deal to find out about this topic.
    I like all of the points you made.

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