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What is a single-skinned building, anyway?

It’s easy to forget sometimes that the whole world isn’t as madly obsessed with timber buildings as we are. We try our best to avoid jargon and to keep things simple, but sometimes we forget. So let’s clear up one of our most-used terms.

How is a single-skinned building constructed?

Quite simply, a single-skinned building has walls made of a single layer of timber, plastic, metal, or whatever your building is made of. 

From the inside out, a shed or summerhouse starts with a frame. The boards that make up the walls and floor attach to this frame. In a single-skinned building, there’s only one layer of boards. The outside walls of the building are also the inside walls of the building. If you drilled a hole through the outside wall, you’d see straight through to the interior of the building.

As a rule of thumb, if there’s a visible frame and the walls look the same inside and outside, a building is single-skinned, like the shed above.

What can I use a single-skinned building for?

Single-skinned buildings are suitable for garden storage, seasonal use, and outbuildings that don’t need to stay 100% watertight. Sheds, summerhouses, and stables are perfect examples of this type of building. 

Why won’t a single-skinned building stay 100% dry?

Single-skinned timber buildings are susceptible to water ingress. This happens when moisture from the air outside, or from rainfall, soaks into the outer wall of the building. Because timber is porous, even when painted, it takes in this water.

If the air is excessively moist, or if there is heavy rainfall, a timber building will take in more water. This can lead to water penetrating through the single wall to the inside of the building.

To minimise water ingress, paint, maintain and air the building regularly. However, it will always happen to some extent in a single-skinned timber building. You must monitor water ingress to prevent mould or water damage. 

How do I avoid water ingress?

A diagram of the Gillies & Mackay U12m2 Garden Room specification, showing all three layers.
The Gillies & Mackay U12m2 Garden Room specification

The surest way to keep a garden building 100% watertight is to avoid a single-skinned construction. These buildings are absolutely fine if you’re willing to monitor and maintain them, and if you have reasonable expectations about how dry they will be.

However, if you’re looking for a building that keeps water firmly on the outside where it belongs, make sure that it has a layered or tiered construction.

How do layered walls keep a building dry?

The real superstar of a layered wall construction isn’t really a layer at all. It’s an air cavity. If there is a gap between the outer cladding and the next layer of the wall, it seriously limits the ability of any moisture to travel between the outer cladding and the inside of the building. 

An air cavity also helps prevent condensation inside the building, as the air acts as an insulator, ensuring that warm air inside the building isn’t hitting a cold wall. More expensive plastic sheds often use this construction method, because plastic sheds are extremely prone to condensation. 

What sort of layered buildings are available?

A Gillies & Mackay timber apex Blackstone Garden Room, with a verandah.
A Building Control-compliant Blackstone Garden Room

Depending on the size of the building, we build three-layered and five-layered walls. 

Our three-layered Under 12m2 Garden Rooms are suitable for year-round use, and in these smaller buildings, those three layers (plus the all-important cavity gap) are more than enough to keep moisture out. 

We build our larger Blackstone Garden Rooms with five layers – they’re fully compliant with Building Standards and just as structurally sound as your home. There’s no way any rain is getting into one of these bad boys!

And our Garages are the superstars that inspired all these upgrades. You see, we built single-skinned Garages for a long time. But guess what happened?

Yup. Water ingress. After far too many calls, emails and repair jobs for single-skinned Garages, we realised that this construction wasn’t good enough for these larger buildings. So we created our three-tier garage specification, a modified Blackstone Garden Room specification, that keeps the water on the outside of the building, where it belongs!

Are single-skinned buildings a waste of time?

Coloured Garden Sheds with open white doors in Perthshire, Scotland.

They most definitely are not! If you’re looking for somewhere to store garden equipment or keep your bikes safe, then a good solid single-skinned building is perfect. 

As long as you’re aware that the building will stay dry most of the time, but not necessarily 100% of the time, you can plan for this. Single-skinned garden buildings need more maintenance than layered buildings, but this maintenance goes a long way towards minimising water ingress. 

If you’re storing expensive power tools or creating a ManCave, avoiding water ingress is higher on your list of priorities.

Fortunately, there’s a garden building out there for everyone. The better-informed you are, the more likely you are to find one that’s perfect for you. 

What is a single-skinned building?

You’re now officially genned-up on single-skinned buildings. One layer of wall material = single-skinned. In a single-skinned timber building water ingress can happen when the weather is particularly wet.

If you need the building to stay bone dry inside, look for a layered construction and an air cavity.

To see examples of both of these types of buildings, come on down and see us at our Show Area. Here you can see single-skinned sheds, three-layered Garages and Garden Rooms, and five-layered Blackstone Garden Rooms – there’s something for everyone!

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