Log Cabin Base Requirements

Log Cabin Base Requirements

Log Cabin Base Requirements are way different from building a garden shed.

Let me explain…

Garden Sheds

When installing a shed, the floor is laid down first, then wall logs or panels are installed on top.

Shed Bases

Log Cabins

When building a log cabin, it is the reverse.  The log cabin is built first, then the wooden floor is installed, this method is known as a ‘floating floor’ and does not come in contact with the log cabin walls.  The floor joists may be and in most cases, are joined to the log cabin foundation beams.

Perimeter Foundation Beams

Foundation Beams

We recommend that all of our log cabins are built using a foundation beam.

As standard, we provide 70mm x 44mm tanalised foundation beams. These are provided to be installed around the edge of the cabin and they sit between the base and the first log.

By using this method, it provides protection for your first layer of the cabin logs. The foundation beams are installed around the log cabin perimeter and below the primary log and act as a sacrificial log ensuring the primary cabin log is kept safely away from any water areas.

If you would like to improve on this, we can also offer, as an option, profiled foundation beams.

As standard, we provide 70mm x 44mm tanalised foundation beams. These are provided to be installed around the edge of the cabin and they sit between the base and the first log.
Profiled Foundation Beams
If you would like to improve on this, we can also offer, as an option, profiled foundation beams.
The same as the profiled beams above but these ones are made of a composite material and will never rot.
Foundation Log Cabin
The foundation beams are installed around the log cabin perimeter and below the primary log and act as a sacrificial log ensuring the primary cabin log is kept safely away from any water areas.

The Perimeter

With the information detailed above, you will now understand that all of the log cabins weight is placed on the perimeter of the log cabin.

So, when building your base, great consideration should be given to this and you must ensure that the perimeter of the base is absolutely solid and has been constructed in such a way as it is suitable for the purpose for which it was built.

The perimeter for the base requirements must have the greatest strength as this is where all the cabins weight is applied.

Base Requirements Level

All of our Log Cabins are manufactured using the very best equipment to create the logs and joints and therefore to remarkably precise tolerances.  They are created for each individual log to be placed on top of one another utilising the precise tongue and groove connection along the logs. The corners are interlocked and are designed to withstand large vertical force.

It has been known for the building and or landscaping companies, to add a slight inclination to the perimeter of the base to help with drainage as they are accustomed to making for terraces and patio areas.  Some building and landscaping companies do this as the norm without forethought and discussion and are really over the moon when they explain to you that you have a 2° incline! This is a problem, a big NO NO!

Effectively, you will be constructing your log cabin on a slope and subjecting it to lateral forces that it was not intended to take.  A log cabin is really not up to handling lateral forces and the sideways forces placed upon it when on any sort of inclination.

The finished result will be a warped and buckled building and will eventually feature split and strained logs.

The worst thing about an uneven and un-level base is that it makes it incredibly difficult to put the whole thing together, so anticipate all kinds of difficulties working with an uneven base:

  • Logs will not seat properly
  • Windows and doors will be squint and not open and shut correctly
  • The roof apex will not sit flush leaving a gap between the roof and the wall
  • Roof boards will not go on straight

If your base is not level the long term problems will be:

  • Warping
  • Twisting
  • Straining
  • Cracking & Splitting

Then, you will contact us promptly during the installation as it’s not going together as it should and in about two or three months after it has been built when it’s all warped and falling apart. We will visit and inspect the base and say we told you about the importance on a level base and we will end up bickering and you won’t even offer me a cup of tea!  So, PLEASE, PLEASE, make sure that the base is 100% level.

So, what if the base isn’t level?

Sometimes there’s not often a great deal you can do about it. Adding a top screed to a concrete base trying to make it completely level seldom works and will crack and disintegrate as pressure is applied to it.

If the base is uneven or not 100% level, you must do something about it before the log cabin can be built.  Options are it is demolished and a new base is formed and started again or another solution must be found.  You can use slithers of high-quality pressure treated timber, using these, you can overcome some discrepancies.  And, if you are going to do this, for goodness sake, make sure that it supports the whole length of a log and not just the corners!

Here’s an example:

Poor Log Cabin Support
This is a log cabin base ‘gone badly wrong’

This is a log cabin base ‘gone badly wrong’

Unfortunately, this is a long story, however, this client had some especially poor builders that built the foundation base they hadn’t a clue what they were doing and didn’t care!

The image above clearly shows their version of levelling up the corner to make up the deficiency in the extremely unlevel base. They doubled up two pieces of plywood to support the corner of a large 70mm cabin.

Not only had the cabin logs sagged across a one-meter length, but the interlocking corner joints were also badly damaged. Even if this botched job had worked, the plywood would have rotted within six to twelve months and the whole thing would have dropped and destroyed the client’s log cabin!

Here is how it is best achieved:

The cabin was completely dismantled and reassembled correctly.  This is how the fault in the base was rectified.  Notice the tanalised timber and that it is being supported along its length and made suitably level.

If this is done, make sure to use timber that is not going to rot and ensure the foundation beam is supported throughout its length and for goodness sake, make sure the entire building is completely level both back to front and side to side!

Log Cabin Footprint

All of Tuindeco’s log cabin measurements are taken from one end of a log to the other.  So a 5.0m wide log cabin is exactly five meters.  The outside edge of the log to the other outside edge is exactly 5.0m.

The base does not need to be exactly this measurement as all the cabins logs have an interlocking corner connection, normally 10cm or less.

So, for example, the base required for a 5.00m wide log cabin is calculated as follows:

  • The overall length of the log =5 meters or 5000mm
  • Interlocking crossover = 10cm or 100mm
  • Log minus interlocking crossover x 2 = 4.8 metres or 4800mm

For this example, we could build our cabin’s base to exactly 4.80m wide and the cabin will sit on it perfectly.  Be very, very careful, there may be a slight deviation in the cement when the shuttering is removed and it may not be as accurate as it should be.  There is absolutely no room for error when making it exactly to the building footprint so it may be smart to add 1cm or 2cm to both sides just in case.

If your builders are good and they can work to exact tolerances, the finished effect is far nicer.  This also has the advantage of ensuring when it rains, water does not land on the base and splashes up making the lower wall section of your attractive newly built log cabin all filthy and dirty.

Water Splash on Logs
Water Splash on Logs

Another great idea when preparing and building a base to the exact size of the cabin footprint is to add a French Drain. A french drain looks incredibly nice and helps to absorb water, preventing it from splashing up and in most cases, helps alleviate the need for guttering. Another advantage can be to cover any of the cement you don’t want to see with the loose stones.

French Drain

Base Requirements Summary

A log cabin base can be pretty much be made out of almost anything and we will get to that in a bit.

However, any base created for any log cabin must follow these criteria:

  • Attention must be paid to the fact that the bulk of the weight being distributed is on the perimeter of the log cabin.
  • Attention must be paid to the weight of the cabin, a 28mm cabin is obviously vastly different from a 92mm log cabin.
  • The base must be 100% level in each and every direction.
  • Ideally, the base should be square.
  • Ideally, the base should be only slightly larger than that of the actual footprint of the log cabin.

Types of Log Cabin Bases

I do hope that after all the above information I have given, you have a bit of an idea of what we are ideally looking for in a log cabin base.

I’m not going to explain how to construct a log cabin base as I am not a builder nor a professional landscaper. I will, however, show you a few different examples of what can be achieved and used.

Small to medium Concrete Base

A base of concrete can be built in several ways. Generally, it can be achieved with timber shuttering. The average small to medium cabin base will be around 10cm – 12cm deep with larger cabin bases being between 15cm to 30cm.

Small to medium concrete base

You can also get a little more complex with a supporting wall made from blockwork or bricks (Bricks are the preferred perimeter material) and infilling the centre area with concrete.

This is a much better option for larger buildings that require a much better weight supporting structure around the perimeter.

If you have a larger cabin, your builder or landscaper should advise reinforcing the concrete with steel, and do NOT forget the perimeter!

Steel Reinforcement in Concrete Base

As for advice on mix ratios, the strength of concrete, I am not the person to ask, there is lots of advice on the internet and it’s probably better you get that information from your experienced builder.

Timber Frame Base

This is done by creating a timber frame supported by vertical posts, or pads positioned at regular intervals. I prefer this method as it is an environmentally friendly solution and is incredibly suitable for areas where the creation of a concrete base is not feasible or when there are steep inclines to overcome.

There are no exact or fast ways of creating this, so I will just show you a couple of examples:

The things I really like about a timber frame base are:

  • It allows excellent ventilation and airflow, therefore the timber will never rot even if it’s not treated.
  • It is a very cost-effective and environmentally friendly solution.
  • If subsidence were over to occur, you can easily jack up the affected area and re-support.
  • This is also an excellent system where natural flooding occurs.
Timber Frame Bases
Log Cabin Timber Frame Base

Adjustable Support Pads

To make levelling a base easier, we have an outstanding product which is available at excellent prices. There are two size options available to choose from, allowing you to level your cabin between 3cm and 14cm. This also provides more flexibility by using a combination of both sizes.

To ensure that you are able to install your log cabin efficiently and with ease, and have it last for many generations to come, then the base must be made to the following criteria;

  • Attention must be paid to the fact that the bulk of the weight being distributed is on the perimeter of the log cabin.
  • Attention must be paid to the weight of the cabin, a 28mm cabin is obviously vastly different from a 92mm log cabin.
  • The base must be 100% level in each and every direction.
  • Ideally, the base should be square.
  • Ideally, the base should be only slightly larger than that of the actual footprint of the log cabin.

This is really important so, pay attention.

If you are building a concrete base, you must add a dampproof membrane either within it, on top of it or both. This will prevent any damp coming up through the base affecting your cabin during the colder, wetter winter months.

Here are some useful diagrams.

DPM DPC Advice
Base configuration when using our profiled foundation beams.

I hope this advice has helped, please feel free to comment and if you are a professional builder or constructor please leave some tips and advice it will be gratefully appreciated.

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