Sheddie,
If you’re here, it’s likely you’ve noticed something in your summerhouse that doesn’t feel quite right and you’re not sure what to do next.
First of all, take a breath. What you’re experiencing is very common with this type of building, and in most cases, it can be understood and managed with the right approach.
We recommend taking a few minutes to read through this page in full before taking action. It will help you understand what you’re seeing and guide you through the steps that usually resolve the issue.
This page is here to guide you through:
- what’s happening
- why it’s happening
- and what you can do about it
So you can feel back in control of your building again.
Your Guarantee
Has Expired
We want to be clear from the outset so there’s no confusion.
All Gillies & Mackay summerhouses are now outside of their guarantee period.
Your building originally came with a one-year unconditional guarantee. Beyond that, ongoing performance relies on regular care and maintenance, particularly in managing moisture and ventilation.
Timber is a natural material, and your summerhouse will respond to its environment over time. With the right care, these buildings can continue to perform well for many years.
Why We Stopped Manufacturing Summerhouses
We made the decision to stop producing summerhouses because we could see a clear shift in what customers needed from their space.
Simply put: people wanted buildings they could use comfortably all year round, with less maintenance and fewer limitations.
A traditional summerhouse is a single-skinned building, and that comes with some natural characteristics:
1
They are seasonal by design
Summerhouses are best suited to use in warmer, drier months.
They can be used in winter, but they won’t perform like a fully insulated space.
2
Moisture is part of how they behave
Because there is no internal wall or cavity, the inside of your building is directly affected by external conditions.
This means:
- moisture in the air can settle inside
- you may notice damp patches or surface mould at times
- this is more common in autumn and winter
3
Timber naturally moves
As weather conditions change, timber expands and contracts.
You may notice:
- doors becoming stiff in wetter months
- doors loosening in drier periods
- small visual changes in boards over time
These are not faults — it’s how natural timber behaves
One of the biggest sources of confusion over the years has been the difference between a summerhouse and a garden room.
Here’s the simplest way to think about it:
In Summary
Garden rooms are specifically designed to eliminate the common challenges that come with single-skinned buildings.
But it’s important to say this clearly:
Your summerhouse is not a poor product.
It’s simply a different type of building – one that requires more hands-on care to perform well over time.
If you’re experiencing an issue, the most important thing is to understand what type of challenge you’re dealing with and how to manage it early.
In the next section, we’ll walk you through the most common scenarios, including:
Problem: Leaks or Water Ingress
This is the most common concern we hear and understandably, it can feel worrying at first. You might look at it and think: “Where is this water coming from? Is something leaking?”
In most cases, what you’re seeing is not a leak, but moisture within the timber. A true leak is usually obvious – a consistent drip.
What you’re more likely experiencing is moisture absorption, where the timber naturally takes in water from the surrounding environment.
Seasonal Weather
(Autumn & Winter)
During wetter months, rain and damp air increase moisture levels. Your summerhouse will absorb some of this moisture, particularly on sides most exposed to wind and rain.
This means:
- one wall more affected than others
- darker patches or damp areas appearing
If your summerhouse is positioned close to fences, walls or hedges – these can restrict airflow.
Without good ventilation around the structure, moisture takes longer to dry out, which allows it to build up.
If your base extends beyond the footprint of the building (e.g. paving slabs), rain can bounce back up onto the timber.
Over time, this repeated exposure increases moisture absorption at the lower levels of the building.
This is why we always recommend a slabbed base made to the size of your summerhouse, with a gravel soakway (as pictured above)
Airflow is your biggest ally.
- Open doors and windows on dry days
- Create cross-ventilation where possible
- Make this part of your routine, especially after periods of rain
- Use moisture absorbers or dehumidifiers
- Avoid keeping the building sealed for long periods
- Allow air to circulate freely inside
Moisture often builds up where airflow is restricted.
- Look behind furniture
- Check corners and lower wall sections
- Move items slightly away from walls to allow air movement
Problem: Mould Forming
Seeing mould inside your summerhouse can feel alarming - especially if it’s appeared suddenly.
It’s one of the most common concerns we hear, and in most cases, it’s completely manageable once understood.
Mould forms when moisture has built up within the building over time, combined with limited airflow.
This is most common:
- after autumn and winter
- during prolonged wet weather
- in areas with little ventilation (corners, behind furniture, shaded spots)
Mould thrives in damp, still environments which is why it can appear more easily in a single-skinned timber building.
It’s important to be clear:
Mould can occur in this type of building but it can be managed and kept under control.
6 Steps to Combat Mould in Your Summerhouse…
read article
Good airflow is your main defence against mould.
If you haven’t already, refer back to the moisture section above and make this part of your regular routine — especially after damp or cold periods.
Mould is much easier to manage when caught early.
- Check regularly, particularly in colder months
- Pay attention to corners and hidden areas
Problem: Timber Rot
Timber rot is more serious than surface-level issues like mould, so it’s important to identify it correctly.
Rot typically appears:
- darker in colour (often black or very dark brown)
- soft or spongy to the touch
- in more advanced cases, the timber may begin to break down or flake away
Unlike mould, which sits on the surface, rot develops within the timber itself.
If your building is painted, it can be harder to spot at first. You may notice:
- a change in appearance
- bubbling or peeling paint
- areas that feel softer than the surrounding timber when pressed
Rot forms when timber has been exposed to persistent moisture over a prolonged period, without the opportunity to properly dry out.
This is typically the result of:
- ongoing moisture build-up
- poor ventilation over time
- untreated or unnoticed water ingress
Timber is a natural material, and if moisture is left unmanaged, rot can develop gradually.
It’s worth noting:
Rot doesn’t appear overnight - it’s usually the result of moisture that hasn’t been addressed early.
Unfortunately, once rot has set in, it cannot be reversed.
The affected timber will need to be removed and replaced to restore the integrity of the building.
How to Replace Rotten Weatherboard on Your Shed (or Summerhouse)
read article
You have a couple of options:
- If you’re comfortable with DIY, many customers choose to carry out repairs themselves
- Alternatively, a local joiner or tradesperson can complete the work for you
Once repaired, the focus should shift to managing moisture effectively.
Refer back to the earlier sections on:
- moisture ingress
- ventilation
- regular checks
This is key to protecting the rest of your building long-term.
Problem: Doors Are Sticking or Not Closing Properly
This is another common behaviour you may notice with a timber summerhouse.
Your doors and windows are made from natural timber, which means they will respond to changes in the weather. As conditions change throughout the year, the timber can expand or contract slightly.
This movement is a normal characteristic of timber buildings.
Dry, warm weather
(typically summer)
In hot and dry conditions, timber contracts slightly.
You may notice:
- doors not quite lining up
- small gaps appearing
- difficulty getting the door latch to catch
Wet or damp weather
(typically autumn and winter)
During wetter months, timber absorbs moisture and expands.
This can cause:
- doors to feel tight
- doors sticking when opening or closing
- increased friction around the frame
Doors should always be fully painted:
- outside face
- inside face
- hinge edges and sides
This protective coating helps reduce moisture absorption and minimises movement in the timber.
In many cases, allowing the timber time to dry will resolve the issue.
You can help this by:
- opening the doors on dry days if possible
- allowing airflow through the building
- giving the timber time to settle as conditions improve
If the door remains tight, a small adjustment may help.
How to Fix Summerhouse Doors That Are Too Tight
read article
If contraction has caused the door to loosen slightly, you can follow the steps in this guide to adjust the fit.
Some customers also choose to add a padbolt for additional closure. As with any fitting attached to timber, this may require occasional adjustment as the building moves with the seasons.
How to Fix Summerhouse Doors That Won’t Close
read article
It’s important not to adjust your doors every time movement occurs.
Timber expands and contracts naturally, and frequent adjustments can cause the door to move out of alignment in the opposite season.
For most buildings:
- one or two adjustments in the first 2–3 years is typical
- after this period, the doors generally settle and movement becomes less noticeable
Keeping an eye on your summerhouse and responding early to small changes will usually prevent issues from escalating.
With doors in particular, a little patience goes a long way. As natural timber responds to the seasons, some movement is expected, and with occasional ventilation or minor adjustment they will usually settle back into place.
Ultimate solution
Upgrade Your Summerhouse
If you’re finding that maintaining your summerhouse is becoming more work than expected, there is another option to consider.
In certain circumstances, it may be possible to upgrade your summerhouse so it performs more like a garden room.
This involves adding additional layers to the building, including:
- a cavity system
- insulation
- internal lining
- uPVC double-glazed windows and doors
These upgrades help to regulate temperature, reduce moisture challenges, and make the building more comfortable to use throughout the year.
It’s important to note that this isn’t possible with every summerhouse, as it depends on the size, structure, and condition of the existing building.
If you’re curious whether this could work for your summerhouse, feel free to get in touch with us at info@gilliesandmackay.com
A summerhouse is a natural timber building, and like any timber structure, it will respond to the environment around it. With the right care and attention, these buildings can continue to perform well and be enjoyed for many years.
The key is staying ahead of small changes – keeping the building well ventilated, protecting the timber with paint, and addressing moisture early before it has a chance to build up.
If you’d like a complete guide to caring for your building, including painting, ventilation, and seasonal maintenance, you can explore our full Summerhouse Aftercare Guide below, or visit the Learning Centre for more aftercare-specific articles.
