Foundations, foundations, foundations.

How to select the right type of foundations for your sauna.


So right here. This blog post. Is actually where it all began.

I’ve not been totally honest with you up until now about the reasons for writing this blog. It was not (as I hoped it has appeared), a long well thought out plan where I came up with the idea of building a sauna and then started documenting the process for prosperity from day one.

Few good things in life are planned so easily and executed upon and this, is no exception.  The actual process for me starting this blog, was this : I started building a sauna at my new house. I spent a long time researching different kinds of foundations to use. I eventually decided on one and started building it. Half way through building my foundations, in the car on the drive home – I came up with this AMAZING blog title “Foundations, foundations, foundations”.

“That would be a great title for a blog post!” I thought, “I could summarise all my learnings about foundations for anyone else about to embark on the same journey!” but one blog post on it’s own? That makes no sense, especially as my other blog is about technology and politics. So. I need a new blog. What should it be about? How about documenting the whole sauna building process?

And thus: was born. It’s not pretty, but that’s actually how it came to be. Everything up until now, has been me going back over all the steps I took up until this point. It’s taken a lot of extra effort just to get to the point where I can write this one blog post – with a clever name, I had to construct a whole blog and write a whole lot of extra content. In fact I am now thinking that I can use this material as the base for a book (there are not many good sauna buildings books out there).

So anyway. Now I will begin. For real. On foundations.

There are several different types of foundations and there are not many websites that provide clear and straightforward guidelines on which to choose and where to get material and know-how to be able to build them, I will try below to summarise the different types and point out their pro’s and cons.

Slab/pad (concrete) foundations


This is probably the most typical recommendation you’ll get from a builder. It basically involves : digging a big square hole, putting down some hardcore (basically cheap rocks) and sharp sand (don’t worry it’s not made from Sean Bean) to level the area, then a moisture barrier and some insulating foam around it, creating some concrete forms around the edges (a wooden frame) and dumping a whole load of concrete on top. If you want to do the fancy version, you can add some bent steel bars into the big hole to give the concrete extra strength (I believe this is called rebar – in the trade). Here is a friendly Australian fellow explaining it in more detail :

Look’s easy right? It’s a bit harder than it looks and there are some potential drawbacks :

  1. It uses a lot of concrete. Concrete is the single most carbon intensive product in the world today, producing concrete creates 5% of global carbon emissions on the planet. So using it sparingly is probably not a bad idea, until we find a good less intensive replacement. So I know your sauna is important and all, but really – is it worth ruining the ecosphere for?
  2. You need to hire a compactor. Yeah, you can get them from diy rental places, but it’s a hassle, you need a stong car that you don’t mind ruining the boot of and you might accidentally flatten one of your feet.
  3. If you change your mind in a few years and want to get rid of the sauna, it’s a pain in the ass to move a concrete slab. Concrete is for life, not just for christmas.
  4. In this video he only digs a hole around 30 cm, which is probably fine in the land down under, but if you have a colder climate, then you need to go down at least 80cm to prevent frost heave (more on this later).

On the plus side,

  1. It’s very stable
  2. It’s easy to build on with other building materials (e.g. brick)
  3. Materials are generally easy to get hold of
  4. Most builders/ diy folk can learn to do it

Trench foundations


Ok, these are probably the second most common foundation type your friendly ‘ello guvnor type builder will throw at you. Fairly straight forward premise, the name sort of gives it away.  This one involves digging a trench (surprise surprise) round the outline of where you want your walls to go.  Then, once you have the trench, you fill it up with concrete like a sort of builders version of a castle moat. Only in this moat, after 48 hours it turns solid as rock and you can lay a couple of courses of brick work on top. So best not to fall in it. Drawbacks of this style of foundation are :

  1. You still use a fair amount of concrete
  2. You have quite a lot of digging to do, although less than the pad
  3. you need to buy bricks
  4. You need a brickie to come along to create you small stable skirt of bricks for you to build on (or you try it yourself, this is harder than it looks)
  5. You still have to dig deep below the frost line to avoid the ground heave

plusses for this style :

  1. also very stable
  2. less concrete use than a pad
  3. less digging than a concrete pad
  4. plenty of tradesman about who will gladly put you one of these together

Pier foundations


Ever been to Brighton Pier?  – (the working one not the burned one that looks like it should be in the final scene of Planet of the apes.)
Seen how it’s held up basically by columns coming out of the sea? Well that’s a pier foundation, true to it’s name. The essential run down of pier foundations are, dig a hole deep enough and stick a big pole coming out of it. Repeat. You want to separate them at regular intervals to the same height – (usually a distance or around 1.5-2 meters is good enough to keep the load distributed).
The pole can be concrete, steel, wood, brick, whatever you fancy. Then when you’re done, drop your house frame on top of it.
That’s it!
Things to remember are to go at least 80cm deep (in Northern Europe), depending on your ground frost depth to avoid ground heave. Also dig a bit deeper and add some gravel to the bottom of the hole this serves to help you level the post but also allow water to run off down into the soil and not pool at the bottom of the post. And also If you are using concrete, you need a form and depending on the height of the piers – to add some rebar (over 50cm out of the ground I would recommend it). There are some great companies that do cardboard forms that you can remove after the concrete has dried. Or if you’re on a budget, nip down to your local hardware store and pick up some cheap wide diameter sewage pipes that also can be used as a form. Here’s a surely American explaining it all with moving pictures:

Drawbacks of Pier foundations are :

  1. You have to dig a deep hole, but only a few.
  2. You have to wait at least 24 hours for the concrete to dry.
  3. It’s hard to move piers if you want to move.

Positives are :

  1. Much less concrete use overall
  2. Very stable and strong structure
  3. Easy & can be done by one person
  4. Inexpensive

Screw foundations


OK, so just to clear up any misconceptions. Screw foundations, have nothing whatsoever to do with fornication. They are infact called so because they use the principle of fastening posts into the ground using a helical ridge. So. Onwards to process. Take a giant metal screw, position it where you would like a foundation post and twist it. Repeat until it is at desired height. Simple. No concrete. No mess. The only tools you need are a big screw driver (or a screw attachment to a JCB). Job done. The big plus of screw foundations is when you’re finished with your building or if you want to move it. It’s a piece of cake. Unscrew and reuse at no extra cost.

Drawbacks :

  1. Expensive

Positives :

  1. Quick
  2. No wet trades
  3. Easily removable

Plinth foundations


Wow, you made it all the way down to Plinth foundations! I’m impressed! You must be serious about your sauna and it’s foundations. Well the great thing is our last stop on the foundation train, plinth foundations, might just be where it’s at in terms, of cost, installation effort, reusability, low carbon footprint. They’ve got it all.
A plinth foundation is s pyramid shaped concrete block, you simply dig a hole a 10 or so centimetres into the ground, put down a moisture barrier, drop in some gravel to bring it back to ground height (you may also need a plastic tray to keep the gravel to stop it spreading) and place your plinth. Hey presto, after laying one of these blocks every 50cm or so under your building, you have a sturdy base with which to position your subfloor. If you live in windy climbs, you may also have to ‘peg’ your building into the floor (that’s right I said, peg, like a tent) to stop if flying away in a strong gust.

Here’s another example of someone laying some plinth foundations (sorry for some reason again it’s an Australian!)

So is it really that easy, no downsides? Well, everything has a downside :

  1. As of writing, these are expensive!  Expect each one to set you back at least 100 euro in europe but handi blocks seem to be much cheaper in the antipodes.
  2. Distribution – where can you get them? A company called swift claims to deliver within the EU but I have no direct experience.
  3. Building pegging is sometimes required.

But on the plus side you have :

  1. Least amount of work
  2. Least amount of experience required
  3. Totally removeable and reuseable once finished

So all in all, Plinths seem like a pretty wise choice for the casual diy’er.

Ground frost

There was a topic I mentioned a couple of times, that I said I would get back to. That topic is ground frost. If you live in northern europe, of the US or anywhere where the temperature drops down to 0 degrees centigrade and below, then you are going to have to take into account ground frost. You see the ground, it has water in it, sometimes in little pools, sometimes distributed in little drops, sometimes just randomly dotted around. This water, when it gets cold, it freezes. What do we know from pre GCSE physics? When water freezes it expands. So when the ground water freezes, that too expands, and it creates force. If your foundations are not anchored in lower that the level of ground to which the frost penetrates, then it will put force on your foundations. That can mean nothing, it can mean your whole concrete pad lifting out of the ground. It can mean after a few years of force, your pier foundations start popping out of the ground like someone hit the eject button. Trust me, it’s bad, so make sure you know the front line for your area (in Berlin here it’s about 80cm) and make sure your foundations go below it, or you use plinth foundations.

Well, that’s it on foundations. I hope that gives you enough information to make the best decision for your sauna and property location. Just incase you’re wondering, we went with self made pier foundations and so that will be our base for the rest of the blog. Good luck!


Size matters…

So once you’ve located where your perfect sauna is going to be. The next thing to figure out, is :

“what will the size and layout of my sauna be?”

Important considerations to take into account here are :

How many people do I want in the sauna at one time?

For example, possibilities include – Just you. You and your girlfriend. You, your girlfriend and her friends. You, your girlfriend, her friends and your friends? You, your girlfriend, her friends, your friends and your dog? (actually this one probably gets you in trouble with the RSPCA). Finally, you, your girlfriend, her friends, your friends and parents? (this one avoid problems with the RSPCA but could result in wierd vibes, so best to steer clear unless you come from a very liberal background).

How many people can lye down at one time?

Some people prefer to sit in the sauna, some prefer to lye down. I myself am a shifter, when the going gets tough and it’s really hot, I often start lying down and then migrate to sitting up. Do you want to be able to lye down? Do you and your girlfriend want to be able to lye down? If you do, then your going to need multiple extended benches to hold those long legs of yours.

Do I want a window?

As mentioned before, windows to outside natural scenes are great ways to relax and take your mind off the skin scorching temperatures you are experiencing in the sauna. If you want a window, make sure it’s on the right wall, looking the right way and that your benches are orientated towards it. There’s little point having a window overlooking next door’s tool shed or a window that you have to crane your head for 15 minutes to look out of.

Where will the electricity for lights and possibly sauna oven come from?

This is not necessarily a problem, but worth bearing in mind, running cables is pretty straightforward, but if for some reason there are only certain places where the oven can be due to electricity, then now is the time to note it down.

Where will the internal drain empty to?

It’s probably pretty likely you are going to want to clean the floor of your sauna at some stage. Although the first time you see a pool of your own sweat on the floor can be fantastically uplifting to realise in voluminous form all the toxins you’ve purged from your body, the second, third, fourth and fiftieth time, it just gets to be a bit gross. Most likely you’re going to want to get a mop down on that surface before long, and where will all that dirty sweat ladled cleaning water go? Down your nicely built floor drain and if said drain is emptying out onto your equally beautiful marble terrace, then you probably want to relocate it somewhere more out of site…

Once you’ve considered all of these questions in careful detail (or you’ve skim read them, looking straight for me to get to the point) you are probably going to find this very helpful :

This link shows all the common varieties of sauna layout and the required sizes from them. Once you have your answers to the previous section, it should be fairly straightforward to look at these plans and pick a design that suits your needs. But wait, is there a creative snowflake out there reading this? Don’t worry, you don’t have to follow these rigid plans, they are only suggestions, feel free to arrange the layout to what suits you best. It’s your sauna, afterall.

Location, location, location

Before you can decide anything else. Like size or materials or sauna type. You have to know where to put your sauna. There are several things to consider about sauna placement and it’s important that you do it as one of the first things before building your own sauna. Sauna placement like it or not will dictate a lot of the later decisions you will have to make.

Here are some of important things to consider:

Internal or External sauna?

Firstly consider your climate. The worst scenario here is that you build your sauna, everything is perfect, but at the time of year you need it the most (the winter), you can’t be bothered to brave the sub arctic temperatures to get to the damn building. You should have built an internal sauna. Having said that, we here in Berlin can get down to -20 degrees C and there is nothing more satisfying than bolting from the warm indoors, to the freezing outdoors to the luxuriously warmth provided by a sauna. If we lived somewhere further north though like Canada or Sweden, I might not be so glib. So choose carefully.

I have tried both, indoors and outdoor saunas. While outdoors tend to be bigger and have a nicer views : indoors can be equally rewarding with their short hops to a cosy fireplace and a couch. What’s important with indoor sauna’s is that you have somewhere to cool off, the outdoor cool off period is vital to a refreshing sauna, and while a cold shower can suffice, there is nothing like starring at the stars on a clear winter’s night fresh from the sauna with steam rising off your skin.

A potential halfway between internal and external is in the basement. In one Swedish house we stayed in the Sauna was in the basement, which was a good idea as winters often dropped below -20 degrees Centigrade, the basement was naturally cool anyway and there was a door in the immediate vicinity to the outside for the cool off.

How far is it from the house?

Assuming you have decided that you are going to build an external sauna (like we have and will be the main focus of this blog) the next question is distance.

Now if you are going to build a sauna building with inclusive hot showers and maybe a bathroom, then a fifteen minute trek from your house may be no biggie. On the other hand if you are just building the sauna as an outhouse, bear in mind the distance from the shower in your house to the sauna. Every sauna starts with a shower so if you have to shower and then go for a fifteen minute trek to your sauna house, you’re probably going to be frozen icicle before you get there. A good rule of thumb here is at a light jog you should be able to get to your sauna in 10-20 seconds.

Sauna Vista

You’re sitting in a Finnish Sauna, stifling ninety degree air is filling your lungs, baking cedar benches scorch your skin as sweat rolls down your cheeks, but you relax as you stare out of a small window to a snow covered landscape. It’s amazing to have a great view, and you can equally exchange snow capped, pine covered mountains for a metropolitan skyline of blinking lights. Having a window with a great view is a strong plus for giving the sauna the edge in terms of holistic experience. Being able to watch nature or natural scenery has been medically proven to be a restorative therapy.

So when thinking about where to put your sauna, make sure you bear in mind what you’re going to be looking at as you sweat away the hours…

Sauna Voyeur

The last grain of sand plumets though the vortex of your sauna timer and releases you to the wild to cool off. You stumble, in a steamy stupor through the sauna door to the outside showers where respite awaits. As your brain quickens with the cold water you notice your slightly strange neighbour (he looks a bit like the guy from the burbs with Tom Hanks) watching you from the window of their house and the euphoria turns to uncomfortable paranoia.

When positioning your sauna and attached facilities make sure you have enough privacy to keep your sauna experience to yourself, watch out for potential neighbours, dog walkers, high buildings and decide accordingly how to place your sauna.

Post sauna vista

When you’ve finished your sauna and showered (hopefully in private) also think about where you want to cool off? Do you have an outdoor terrace? What is the view like there? Are them some chairs with good views to relax in after? A sauna is only as good as it’s cool down period, so make sure to have somewhere to go afterwards to reacclimatise. This can also be indoors, I would highly recommend a comfy sofa adjacent to a crackling wood fireplace and cold glass of blackcurrant juice nearby.

Potential danger sites

It is unwise to locate your sauna, in the vicinity of or close to a potential danger site. In a post sauna euphoria, there is a much higher chance of an accident. Remember, with a sauna you are essentially benefiting from temporarily frying your brain, therefore your not quite as adept at traversing the world as well as before.

So make sure you avoid any of the following : Large vertical drops, fast flowing water or rapids, small staircases, sharp rocks, hot firepits, rope bridges, high speed motorways, train tracks, shooting ranges, heavy machinery, angry bulls, knife wielding monkeys and belligerent horned goats.

Boring bureaucracy

Usually external saunas (or internal) do not requirement planning permission. That is, if they are small enough to be classed as an outbuilding on the same lines as a shed. If you intend on build a three story, infinity pool roof, tropical indoor garden, five hundred people plus sauna house, then a trip to the local planning authority might be in order, and if they say no, it’s not the end of the world, just consider down scoping your plans a bit. The infinity pool can always be done at a later phase!

Let’s get hot and sweaty.

Why am I writing this blog?

When I was twenty six, I had my first real sauna experience.

I was an English immigrant living in Germany, it was my first year living on the continent and enough time had past that I had grown accustomed enough to the teutonic sensibilities surrounding nudity that I decided to shed my traditional prudishness and try it for myself.

“We’re all the same underneath” my Grandmother had once told my in a caravan as she changed outfits on a family holiday to the south of France when I was five. I hadn’t really believed her then, she had bumps where I had none and funny wrinkly skin, but now, twenty one years later I was finally willing to test her thesis.

We were staying in an east German seaside resort called Henningsdorf a few miles from the Polish border in a hotel called “Upstalboom” the name itself conjuring up images of some kind of crazy experiential explosion. It was early autumn and our last sea trip before the harsh Berlin winter set in, the weather was dramatically overcast and drizzly. Fortunately our hotel had an indoor heated pool and as most modern hotels do a sauna. It was a Finish Sauna, 95 degrees centigrade of dry heat and attached was a tiled blue room with two cold showers, a suspended bucket of cold water and a well of ice.

It was time to start a new chapter of experience in my life. Let’s get hot and sweaty I thought as I quickly pulled off my shorts, removed my dressing gown let everything hang lose and enter the mysterious wooden kingdom. An elderly Danish couple were already present as I laid down my towel on the scorching wooden benches. Their skin sparkled with a veil of sweat that showed they had already been there for some time. As my skin started itself to relinquish it’s of toxins by bubbling up sweat like a spring bubbling up fresh water, I began to understand the regenerative appeal of getting really hot. After 15 minutes of a host of new bodily sensations associated with extremely hot environments from breathing problems to dizziness I stumbled out. Giddily I moved from the warmth to the arctic tile room and a pull of the cord of the lofty bucket drenched my simmering skin with a wave of life affirming ice water.

This was my first sauna, and the first step on a path I had not been down before.

Now five years later, I am building my own sauna and this blog is dedicated to the trials and learnings that go with it.