The Importance of Expansion Gaps

What are expansion gaps?

Expansion gaps are gaps purposefully left when building or fitting timber products to allow the wood to move naturally without causing damage. Hardwood timbers, especially oak, are very strong and can cause catastrophic damage when they expand.

The nature of wood and moisture

When timber takes in moisture, it swells. When it loses moisture, it shrinks. Warping can occur across the width and sometimes length of the timber if moisture changes are uneven.

Other factors that can affect how much timber will move can include the type of wood, the size, grain and even what part of the tree trunk the wood is from.

Expansion Gaps in Ledged Doors

As our ledged doors are made from solid timber, we have to be very careful with how we manufacture each door. Our doors are designed to be fitted in commercial and residential properties, and so must be able to withstand natural moisture in the air. Solid timber in areas such as kitchens and bathrooms, where moisture levels are higher, are the most at risk of movement.

Particular care is taken with oak doors, as oak has a moisture movement of ‘Medium’.

In order to safely construct a door made from solid timber, our method is to leave an average of 2mm gap between each tongue and groove vertical board. This means the boards can expand and contract as they take in and lose moisture, without affecting the structure of the door.

What happens if the oak has no room to expand?

Expansion Gaps With Solid Oak Flooring

When fitting our solid oak flooring we recommend leaving a 15mm expansion gap around the room, this allows the oak lengths to expand safely. Without sufficient room left around the perimeter, expanding solid timber can cause damage to walls.

To cover the gaps, you can use our oak scotia bead to finish your room off nicely.

Expansion Gaps With External Door Sets

As a general rule of thumb, we allow a 4mm gap per side between the door and frame. Using adjustable 3D hinges means you can allow for constant changing gaps as the timber moves with the weather changes.