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When log cabin gaps start appearing, it’s completely natural to panic. Whether daylight is peeking through the walls or you feel a sudden draught, your first instinct is likely to head online and search for how to fill gaps in a log cabin.
You might be tempted to run to the hardware store for a tube of log cabin gap filler or heavy-duty sealant. But before you do, stop!
The truth Here at Garden Buildings Direct, our customer service team talks to log cabin owners every day. We’re here to bust a major myth. The truth is: log cabin gaps should not be “filled”. They should be closed. Using chemical fillers is often the worst thing you can do for an interlocking log cabin. In this guide, we’ll explain why sealing a log cabin with caulk causes more harm than good, and share the correct, structural methods to resolve gaps.
The Myth of Log Cabin Sealant and Caulk
If you are researching how to seal a log cabin, you might have seen recommendations for using log cabin caulk or expanding foam. We highly advise against this.
Interlocking log cabins are designed to move. The natural timber expands and contracts as the unpredictable UK weather shifts between warm, humid summers and cold, wet winters. If you use a gap filler or silicone to glue interlocking logs together, you restrict this natural movement.
When the wood inevitably tries to expand or contract, the restrictive sealant will cause the timber to split, warp, and crack. This causes permanent structural damage.
Our Technical Team’s Golden Rule: You should never use a gap filler or sealant between interlocking logs unless a physical piece of the timber has broken off.
Why Are Gaps Appearing in My Cabin?
If you shouldn’t use filler, what is actually causing the gaps? In our experience, it usually comes down to three structural reasons:
- Natural Settling: When a cabin is brand new, the logs need time to settle into place.
- Restricted Movement: If window frames, door frames, or storm braces have been screwed too tightly across multiple wall logs, the logs are pinned in place and cannot drop down as they settle.
- Improper Assembly: Sometimes, during the initial build, logs are not knocked down tightly enough.
The Correct Way to Fix Log Cabin Wall Gaps
If you have gaps in your log cabin walls, the answer is almost always adjustment, not filler. Due to the nature of timber and the interlocking style, your building will naturally want to settle and move.
Excessive dry conditions can cause shrinkage, while wet conditions cause expansion. If your vertical framing is holding the boards in position, the timber cannot drop as it settles, which leaves a visible gap.
To close the gaps in your interlocking walls, follow these official maintenance steps from our technical team:
- Remove vertical restrictions: Temporarily remove all vertical framing. This includes all items holding the vertical height, such as window frames, door frames, standard framing, and even any fixed cupboards you have installed.
- Let the cabin settle: Simply by removing these vertical restrictions, you will allow the building’s side and back walls to re-settle and find their natural level. The interlocking boards will naturally drop down, closing the gaps completely.
- Re-fix the framing: Once the building has settled into its new position and the gaps are fully closed, re-fix all the vertical framing to the wall boards.
- Trim if necessary: Because the wall height has naturally dropped to close the gap, you may find that your vertical framing is now slightly too long. In some instances, the framing may require minimal trimming to fit properly.
Checking your building regularly and re-treating it bi-annually will ensure this movement remains minimal in the future!
Dealing with Roof Gaps
Are the gaps appearing in your roof boards rather than your walls? This requires a completely different approach.
Gaps between roof boards are rarely caused by natural timber movement. Instead, they are usually the result of improper installation, missing hardware, or failing roof felt. If the original builder didn’t put nails or screws into every single board, the timber can easily lift and separate over time.
More commonly, if your roof felt has degraded or was installed incorrectly, water will find its way in. This moisture causes the roof boards to swell, warp, and eventually pull apart. To fix this, you must secure the loose boards with new screws and completely replace your roof felt to restore the watertight seal.
If your felt is starting to fail, don’t wait for the rot to set in. You can pick up high-quality, weather-resistant roof felt to protect your structure. For a step-by-step guide on getting the job done right, check out our guide on How to Felt a Shed Roof.
When is it Time for a Replacement?
Knowing how to properly maintain your log cabin ensures it stays structurally sound for years. However, if previous owners made the mistake of filling the walls with expanding foam, or if years of failing roof felt have caused severe water ingress, rot, and uneven settling, the structure may be beyond repair.
If your logs are severely split, soft from rot, or permanently warped out of shape, no amount of adjustment will save them. In these cases, investing in a durable, brand-new replacement log cabin is the safest and most cost-effective solution.
If your current cabin has reached the end of its life, discover our bestselling BillyOh Fraya Log Cabin or browse our extensive range of modern, interlocking log cabins designed to stand the test of time.
