Log Cabin Wall Thickness Explained, and How to Insulate a Log Cabin

When you shop for a log cabin, the first number you'll see is usually the wall thickness: 19mm, 28mm, 34mm, 44mm or 70mm. It affects how strong the cabin is, how it holds heat, how big it can be and how you can use it. This guide explains what each thickness is good for, so you can compare cabins with confidence.

What does wall thickness mean?

A log cabin is built from solid timber logs that slot into each other, both along their length (tongue and groove) and at the corners (notched joints). The wall thickness is the thickness of those logs, and so the thickness of the wall.

That's different from a shed or summerhouse, where thin boards (cladding) are nailed to a timber frame. Shed cladding is usually 12–20mm thick. Some sheds use "loglap" cladding, which looks like logs from the outside but is still cladding on a frame, not a true log wall.

Wall thickness at a glance

These are general guides that apply across the industry. How a particular cabin performs also depends on its roof, floor, glazing, doors and how well it's built and maintained.

19mm and 28mm: light use and summer rooms

Thinner logs make lighter, more affordable cabins. They're ideal for storage, a children's playhouse or a summerhouse you'll mostly use on warm days. Because the logs are thinner, these cabins are normally kept smaller, as long, thin walls are less rigid. They warm up quickly in the sun but lose heat quickly too.

34mm: the step up

34mm logs are noticeably more solid, and allow larger buildings with more doors and windows. They're a good middle ground for a hobby room or garden room used through spring, summer and autumn.

44mm: the all-rounder for garden rooms

44mm is where many buyers land for a garden room, home office, gym or workshop. The thicker logs give:

• More strength and stability, so the cabin can be larger and carry bigger glazed doors.
• Better warmth than thinner logs, as more timber holds heat for longer.
• Better sound insulation, useful for a music room, gym or video calls.
• A more solid feel, with heavier doors and a sturdier build overall.

70mm: heavy-duty and premium

70mm logs are the heavyweights. They're used for large cabins and buildings where extra strength and thermal mass are wanted. They are heavier to handle and need a strong, well-prepared base. For most garden rooms, 44mm with good insulation in the floor and roof is a practical alternative.

The thicknesses we sell

Our log cabins come from Power Sheds and Shire. Between them, we sell all five thicknesses:

• 19mm: ready-designed Shire cabins. Best for storage, playrooms and summer or occasional use.
• 28mm: ready-designed Shire and Power Sheds cabins, including workshop versions. Good for more regular use from spring to autumn.
• 34mm: a made-to-order choice on many Shire cabins. A step up for larger summer rooms and garden rooms.
• 44mm: Power Sheds cabins in apex, pent and chalet styles, including chalet cabins, combi cabins with built-in storage and cabin garages, plus several Shire cabins. The choice for a garden room or office used all year, with insulation.
• 70mm: a made-to-order choice on many Shire cabins. For large cabins and the most solid build.

On made-to-order Shire cabins, you choose the wall thickness on the product page. The options show exactly what's available for that model.

Many Power Sheds cabins come with double toughened glazing, uPVC or aluminium doors and windows, and an EPDM rubber roof. Power Sheds log cabins come with free kerbside delivery, craned off the lorry on a pallet, as a self-assembly kit. Shire log cabins include delivery to Shire's standard area, with a surcharge for some areas further afield that we confirm before you order. They come flat-packed, or you can choose to have them assembled by Shire. See our Power Sheds buying guide or design your own with the log cabin configurator.

Does a thicker wall mean a warmer cabin?

Yes, but only up to a point. Timber is a natural insulator and a thicker log holds heat better than a thin one. But even a 70mm solid log wall does not insulate as well as a modern insulated house wall. Heat also escapes through the roof, the floor and the glazing, often more than through the walls.

So if you want to use a cabin comfortably in winter, the biggest improvements usually come from:

• Insulating the roof, as heat rises.
• Insulating the floor, which makes the room feel much warmer underfoot.
• Double glazing and well-fitting doors.
• Heating and ventilation, to keep the room warm and stop condensation.

Choose a thicker log for strength, size and feel. Choose insulation for warmth. Our garden office buyer's guide covers insulation, heating and electrics in more detail.

How to insulate a log cabin

If you plan to use a log cabin through the winter, insulation is the single biggest upgrade you can make. It's much easier to fit floor and roof insulation while the cabin is being built than to add it afterwards, so decide before delivery day.

1. Insulate the floor. Insulation boards fit between the floor bearers, with a damp-proof layer beneath to stop ground moisture reaching the floor. A warm floor makes the biggest difference to how comfortable the room feels.
2. Insulate the roof. Heat rises, so an uninsulated roof loses a lot of warmth. Insulation boards go into the roof as it's built.
3. Think carefully about the walls. Solid 44mm logs are often left as they are. If you want to line or insulate the walls, use a framework with slotted fixings so the logs can still move with the seasons, and never fix panelling tightly across several logs.
4. Glazing and doors. Double glazing and well-fitting doors stop a lot of heat escaping. Many of the cabins we sell come with double toughened glazing.
5. Ventilate. A well-insulated room still needs fresh air, or moisture from breathing and heating condenses on cold glass. Open a window or vent for a few minutes each day.
6. Heating and electrics. A small electric heater is usually enough in an insulated cabin. Power must be installed by a qualified, registered electrician. See our insulated sheds with electricity guide.

For Power Sheds 44mm log cabins, the Power Sheds Floor & Roof Log Cabin Insulation with DPC gives you 25mm foil-backed PIR insulation boards for the floor and roof, supplied with a DPC (damp proof course) and delivered with your cabin. It suits the Retreat, Snug, Combi, Manor and Aluminium models, but isn't available for log cabin garages. Choose the size exactly as it's written on the cabin you're ordering, and ask us if you're not sure.

Slot-together log cabins: how do log cabins stay together?

Log cabins are often called slot-together or interlocking cabins, because the walls are built without a frame. Each log has a tongue along one edge and a groove along the other, so it slots onto the log below, and the ends are notched so the logs lock together at the corners. The walls go up one course at a time, and the weight of the logs, the corner joints and the roof hold the building together.

• The logs need room to move. Solid timber swells and shrinks with the seasons, so the logs aren't fixed rigidly to each other. That's why you shouldn't screw anything across several logs (see below).
• The first course matters most. If the bottom logs aren't level and square, every course above will be out too, so the base must be level before you start.
• It's a job for at least two people. The logs are long and heavy. Follow the manufacturer's instructions step by step.

All the Power Sheds cabins we sell arrive as a self-assembly kit, craned off at your kerbside on a pallet. The Power Apex Log Cabin, for example, is supplied untreated apart from its pressure-treated floor bearers, with a 5-litre tub of exterior wood preserver to apply as soon as possible after assembly. If you'd rather not build it yourself, ask us and we'll help you find an installer.

Log cabins move, whatever the thickness

Solid timber takes in moisture in wet weather and dries out in warm weather, so the logs swell and shrink a little through the year. A well-designed cabin allows for this. A few things to know:

• Don't screw shelves, cupboards or panelling across several logs in a way that stops them moving. Use slotted fixings or fix to one log only.
• Door and window frames are designed with small gaps above them for settling. Don't fill these.
• Treat the timber inside and out soon after assembly, to slow moisture changes. See our timber care guide.
• Build on a firm, level base, as a cabin that isn't square will have sticking doors. See choosing a base.

Does wall thickness affect planning permission?

No. Planning rules are about height, position and use, not wall thickness. The height rules matter most: in England, a building within 2 metres of a boundary must be no more than 2.5m high (Planning Portal). Several of the 44mm cabins we sell are designed to stay under 2.5m. Read our planning permission guide.

Common questions

What thickness log cabin do I need for a home office?

A 44mm log cabin is a popular choice for a home office, as it's strong enough for larger doors and windows and holds warmth well. For comfortable use in winter, add insulation to the floor and roof, plus heating.

Is a 28mm log cabin warm enough for winter?

A 28mm cabin is best suited to spring-to-autumn use. It will lose heat quickly in winter, so it's better for storage, hobbies or summer use unless you insulate and heat it.

Is 44mm better than 34mm?

A 44mm log is thicker, stronger and holds heat better than 34mm, and it allows larger cabins with bigger glazed doors. 34mm is a good choice for a garden room used mainly in the warmer months.

Do log cabins need insulating?

For year-round use, yes. Insulating the roof and floor makes the biggest difference, because a solid log wall alone does not insulate as well as a modern house wall.

How do you insulate a log cabin?

Start with the floor and roof, as they make the biggest difference. Fit insulation boards between the floor bearers with a damp-proof layer beneath, and insulation in the roof as it's built. Add double glazing, keep the room ventilated and have any electrics fitted by a registered electrician. It's easiest to do this while the cabin is being built.

Can you insulate log cabin walls?

Yes, but the logs must still be free to move as they swell and shrink through the year. Use a framework with slotted fixings rather than fixing panelling tightly across several logs. The floor and roof make the biggest difference, so start there.

What is a slot-together log cabin?

It's a log cabin whose walls are built from interlocking logs rather than a frame. Each log has a tongue and groove so it slots onto the one below, and notched ends lock the logs together at the corners. The weight of the logs, the corner joints and the roof hold the building together, while still letting the timber move with the seasons.

Can I build a log cabin myself?

Yes. Most of the log cabins we sell come as self-assembly kits, and Shire cabins can also be assembled by Shire. To build one yourself, you'll need a level, fully set base, at least two people and a careful read of the instructions, as the first course must be perfectly level and square. If you'd rather not build it yourself, ask us and we'll help you find an installer.