Thursday, 10 May 2012

The Base

The base of a log cabin is very important as it has a number of major structural effects. If the load isn't correctly balanced, your cabin may warp or even break. I did a fair amount of research before picking my base.

One thing to note with my build is that I was placing the new log cabin in place of an old shed, which was sat on paving slabs. Today, I broke a hole in the old shed floor to inspect the state of its base. While I wont be laying my cabin on the existing slabs, I needed to see how the ground was. Thankfully it was completely bone dry (surprising considering we've had the wettest few weeks in years!). With this in mind, I can now dismantle the old shed, leaving the ground covered with a tarpaulin sheet until the rain stops and I can lay the new base.

I'll explain in detail what I'm planning to do later in this post, but first, lets talk about the different types of base that can be used for a log cabin or garden office.

Choosing A Base

The first base type is the most obvious: 

Concrete Base

A concrete base is probably the most stable way to set up any shed. If you choose to go for a concrete base, you first need to dig out the land and level it, then place wooden shutter boards around the edge, do measurements throughout to make sure you've got the right size. 

Once your shuttering is in place, lay a damp proof membrane. This will stop anything coming up through the concrete and help to keep it dry. 

You can now lay your concrete. Depending on how heavy your building is will depend on how thick it should be. Realistically most garden office / log cabin structures are fine with 4 inches (10 cm). You can use ready-mixed bags from the likes of Wickes and Homebase if you wish, these work fine. Its usually best to see if you can get a deal on a wet concrete delivery as in some cases it can be cheaper. I personally wasn't able to find a good deal on this for my build when I first started researching.

There are a few important points to note with a concrete base:
  • Try not to make your base any bigger than your shed. This encourages water to collect.
  • Ideally, you should try and have the base above ground, so it's effectively 4 inches of raised concrete. This does wonders to stop water.
  • The concrete can take up to a month to fully set, however in most cases should be fine to build on after 48 hours.
  • Concrete actually loves water, so dont be too worried if it rains after you've laid it, it'll only make your base stronger.
  • If you are extending an existing concrete base, drill into the sides of the old base and add metal supports, this will help bond the two bases together and prevent them separating.

Wooden Base

I cant stress how much of a bad idea this is if you want your log cabin to last. A wooden base has very little support and will basically be completely rotten within a few years. I'm not going to go into detail on how to erect a wooden base, however I can only say this: dont do it.

Rased Concrete Base

Think about how a pier works, this method works in a similar fashion. You basically create concrete elevated molds (you can buy them ready made) and then place your wooden base on top of these, raising the log cabin up significantly. 

The idea is that you add these concrete blocks under the base, and it created a strong foundation, way off of the ground. 

A very similar method is offered by a few select garden companies that uses metal pads and poles to raise the base.

Plastic Base

Now, this is the method I chose to go with. But before I go into detail, you need to know that there are more than one type of plastic base. There is 'Ecobase' style bases which aren't very thick (between 3 and 6 cm) and a more stable variation called 'HawkLok' or sometimes 'Forest Plastic Base', this is a much thicker, sturdier method where instead of ramming pea shingles into each hold (presumably to hold everything together), the plastic 'pads' each lock into each other, creating a sold, strong pad which acts much like a solid concrete pad. 

When I first looked into this, I immediately dismissed a plastic base as being a bad idea, but the HawkLok style bas is actually pretty clever. It's been tested to apparently support over 28 tons per pad, and can be moved around and reused. For me, it worked out cheaper than a concrete base, and allows me to put it together myself in a matter of hours.

You start by digging out your plot (which is actually optional if you want the shed rased even more). You then place a layer of sand (again, optional but recommended) followed by a damp-proof membrane. You then lay your plastic bads on the membrane and lock them into place, once done you can move it around to get the correct position.

At this point, the base is complete...much quicker and simpler. I'll be doing a full review (and walkthrough) of the base once I get started (assuming the rain actually stops at some point!!)

I had many discussions with members of DIY forums and like myself, many thought the plastic bases were a silly idea and were only intended for small, light sheds, but they work just as well as a concrete base, and theoretically should be even better as they allow for a bit more air circulation, shouldn't get anywhere near as cold as concrete does, and can be reused. Only time will tell just how good they are though!


  1. Interesting comments about the plastic floor. Can i ask, how stable is it? and how flat on its top surface is it? I was looking at a cabin that was around 4m x 3.5m and didn't want to leave behind the legacy of a concrete base (i may change my mind in 10 years time) :)

    1. It's a hell of a lot more stable than I thought it would be. Initially before the shed was on it, there was a lot of movement if you stood on it, however its compacted into the sand really well and has created a very solid structure, you'd think it was on concrete!

      The only thing I will say is dont underestimate the amount of sand you'll need. I ended up having to lift it up again before the shed came to add about 5 bags of sand and 1 bag of cement. Once you get it perfectly level it's great. So much quicker and easier than a concrete base.

      One thing I do plan on doing however is going around the edges with concrete as the base is 12x8 but the walls of the shed are ever so slightly less than that, so to stop rodents I was basically just going to seal up the edges. Because its only going on top of the plastic base, it should be relatively easy to remove such a small amount if you ever take the base up.

  2. I'm also interested in using a plastic base - can you tell me, two years on, are you still pleased with it?

  3. The hawklock base' has been great. I've had no issues at all with it. It's definitely helped if anything as it allows air to flow under the structure, preventing damp issues.

    I'm actually about to replace another shed in the garden (just a small basic 6x8 shed) and we're going to use a plastic base on that as it's so much quicker and cheaper.

  4. Hi, I'm planning a summerhouse of the same dimensions as yours, at the moment just levelling the ground but very tempted to try the Hawklok as I will have to do it on my own. Trying to find sensible information about concrete and the costs involved is proving tricky so I'm not having much luck making a comparison. Can I ask what function the sand serves as well? Thanks, Laura, London.

  5. can i also ask whats the sand for and the cement in the base? most instructions i see use some gravel to fill it?