How to install a timber frame base for a log cabin or summerhouse

A timber frame base provides you with a strong, raised platform for your garden building to sit on and, when built correctly, offers a stable, well-drained foundation that will protect your log cabin from ground moisture. 

In this blog, we’ll explain everything you need to know about laying a timber frame base for your log cabin or summerhouse. We’ll show you the tools and materials you need, how to build and level the frame and common mistakes to avoid helping you build a strong and long-lasting base for your garden building.

Watch our video for a step-by-step guide:

What is a timber frame base?

A timber frame base is a raised framework constructed from pressure treated timber that provides your garden building with a solid, level surface. This type of base is built using a timber frame placed on a stable, well drained surface or raised slightly above the ground using paving slabs, concrete blocks or adjustable supports. 

One of the biggest advantages of using a timber frame base is that it raises your garden building slightly off the ground which helps to improve airflow underneath the building and reduces the risk of moisture gathering on the timber, which can protect the base and prolong the life of your garden building. 

A timber frame base is also perfect for gardens with a slight slope because the frame can be adjusted and supported at different heights. 

Whilst a timber base is a great option, it’s essential that it’s built properly and the frame is strong enough to support the full weight of the building, completely level and properly supported underneath. If the frame is uneven or unsupported, it can lead to problems during installation and may affect how well your log cabin or summerhouse performs over time.

Is a timber frame base right for your garden building?

A timber frame base is a great option for many log cabins and summerhouses but it’s not always the right choice for every garden or every type of building. 

This type of base tends to be quicker and more cost-effective to install than a concrete base which makes it popular for smaller and medium sized garden buildings. It can also be a good solution if you want to avoid major groundwork or if your garden is uneven. 

A timber frame base is also raised off the ground which improves airflow under your log or summerhouse which can be useful if your garden is usually damp or is a space where surface water collects after heavy rain.

There are some situations where a timber frame base may not be the best option such as: 

• When you’re installing a very large or heavy log cabin 

• You intend to use your garden building as a permanent office, residential space or will be using it heavily 

• The ground in your garden is soft, unstable or prone to movement 

• Your garden is in an area that regularly floods or becomes waterlogged 

Our larger log cabins tend to be much heavier and so place more pressure on the base so a concrete base may offer a better support in this case. 

If you’re not sure which base is right for your chosen garden building, check the size and weight of the model and look at the recommended base type. For further help and guidance, chat to our customer service team who will be happy to help.

Building your timber frame base

Once you’ve decided this is the right base for your log cabin, you can start building the frame. Here’s a step-by-step guide for building a stable, level and solid garden building base.

Step one: Tools and materials

Before you start building your base, you’ll need the materials. 

For our log cabin construction, we’re using 6 x 2” (150mm x 50mm) pressure treated timber planks to build our base. If you have a larger log cabin, we recommend using thicker timber to support the additional weight of the building. 

You’ll also need: 

• 18mm screws 

• 120mm screws 

• Joint hangers 

• 50mm galvanised screws 

• Weed membrane 

• Spirit level 

• Builder’s square 

• Cordless drill with an array of bits 

• Hammer 

• Tape measure 

You’ll need to work out how much timber you’ll need and the easiest way to do this is to start with the footprint of your log cabin or summerhouse. 

For example, for a 3 x 3m building, your timber frame base will need to be the same size. You’ll need pieces of wood for the outer perimeter of the base and enough for internal joists spaced 400-600mm inside the frame. 

Cut the wood you need to size so it can be easily screwed together once you’re ready.

Step two: Choose the location and prepare the ground

If you haven’t already, you’ll need to choose the exact location for your log cabin or summerhouse so you can prepare the base. There is very little groundwork required for a timber frame base, all you need is patio slabs or similar to support the timber frame base pads you’ll use to separate your timber base from the ground. The patio slabs should be laid out to support the main parts of your base such as the corners and the middle.

Make sure you have a flat area to work with and, once it’s prepared, lay a weed membrane across the whole area to prevent unwanted growth occurring underneath your building and to protect it in the future.

Step three: Build the outer timber frame

Start by assembling the outer timber frame. Lay the pressure treated timber around the outside area of your prepared location. Screw the four parts together to create your frame.

Before you continue, check the frame is level, square and matches the dimensions of your log cabin or summerhouse.

Use a timber frame base pad on each corner of the base for support. These can be adjusted so you don’t need to worry about the patio slabs you’ve laid being completely level.

Step four: Add the internal joists

Once the outer frame is ready, fit the internal joists with 400mm (16”) between each one. These fit from the front to the back of the base with noggins in between. We recommend adding two noggins per layer.

The joists will need to be secured with joist hangers to secure them in place, but while you’re building the frame, we recommend securing with heavy duty screws so you can check everything is square before finishing the base.

After the joists have been added, you will need enough timber base frame pads to support your building. We recommend one under every other joist, but this will depend on the size of your building. Larger buildings will require more.

Step five: Secure secondary layer around the outside of the building

As part of our process, we made the frame of the timber base slightly smaller than required to enable us to fit the joists and noggins correctly. We recommend adding a secondary layer of timber around the outside perimeter. This ensures that anywhere the walls of the log cabin will be pressing down, there will be two layers of timbers laminated together, making it extra strong around the outside perimeter.

Common mistakes to avoid when building a timber frame base

When building your timber frame base, there are a few mistakes to avoid that can cause issues with the installation of your log cabin or summerhouse or cause problems in the future, affecting the longevity of your garden building. 

Here are some of the common mistakes to avoid:

Using untreated timber

We recommend using pressure treated timber as untreated timber can quickly rot when used outdoors which will affect the stability of your garden building. If your base isn’t stable, you may experience problems with the timber of your building warping, splitting or cracking in the future.

Not checking the frame is square

If the frame is not completely square, your log cabin might not fit properly. Always use a builder’s square or check the diagonal measurements with a tape measure before fixing everything in place.

Supports too far apart

If the supports of your base are spaced too widely apart, your timber frame may sag over time. Ensure your frame is fully supported underneath all the joists before installing your log cabin or summerhouse.

Forgetting about drainage

Even though your base will be slightly raised off the ground, poor drainage can still cause problems so always make sure water can drain away beneath the base to avoid these in the future.

Final checks before you start building your log cabin or summerhouse

Now you’ve built the base for your log cabin or summerhouse, you can start thinking about installation. We recommend carrying out final checks before you start including:

• Ensuring the base is level 

• Ensuring the frame is square 

• Securing all supports 

• Checking there is enough drainage 

• Ensuring you have a solid and flat surface to start with 

Once you’ve carried out these final checks, you’re ready to start building. 

Spending the time building a solid base will save a huge amount of time in the future and helps you to protect the longevity of your garden building and ensure it looks and performs exactly as it should.

Read the next blog in our series to learn more about installing the damp proof course for your log cabin or summerhouse.

If you’re unsure what type of base is right for your garden building or you’d like additional advice, please contact our customer service team.