What is the Recommended Gap Between Decking Boards?

M. John

Building a deck in your home can beautify your home as well as increase its value.  But if you don’t leave gaps between the decking boards, the deckings will get damaged. So, when laying your ultradecking board, you need to space them properly. If so, what is the recommended gap between decking boards?

Why You Should Leave Gap Between Decking Boards

grey composite decking flooring
A stunning and well laid composite decking with gaps in between

Spacing the decking board is very important. Your decking boards can warp, crack or splinter if you fall to leave gaps between the boards. See more reasons we recommend you leave gaps between composite decking boards,

Expansion and Contraction

Both composite decking and wood expand during temperature change. Wood decking boards will swell and absorb moisture when humidity is high. But will also reduce in size when humidity becomes low.

Composite boards, on the other hand, will expand when the temperature is high and contract when the weather is cool.

If you leave gaps when installing your decking board, it will create room for expansion and contraction of the deckings. Your decking will not warp, crack or splinter if there is a gap between the decking boards.

Allows Water Drainage

The gaps between the decking board allow water to drain easily from the deck surface. It also makes cleaning the decking easier. Water will be able to drain easily, thereby preventing the accumulation of water. It will also keep your decking board from getting rot as water can hasten wood decay.

Improve Air Circulation

If your decking frame is moist, it can damage the wood over time. It can also hasten the mould growth on your decking. But, when you leave a gap between your decking boards, it will aid air circulation. It, in turn, will keep your joist dry and free from moisture.

Factors That Influence a Decking Spacing

Wood Type

Woods tend to swell when humidity is high and shrinks when humidity is low. Pressure-treated pines contain a lot of moisture and will shrink when it gets dry.  Hardwood like ipe and softwood like cedar and redwood also absorb moisture with different expanding and contracting properties.

Weather Conditions

Weather conditions can affect your decking board. In summer, where the weather is hot, composite boards tend to expand. And if there is no space between the deckings, the board can warp. Apart from that, the decking can also shift from its original position.

Therefore, you will need to leave spaces between composite decking to allow for thermal expansion. When there is a gap between the decking boards, the board will expand freely without touching each other.

When installing your decking, the recommended gap between between the decking boards should be between ⅛ inch and ¼ inch. Composite deckings expand and contract due to temperature change; the recommended gap you should leave between the composite deckings should be ⅛ inch apart.

Wood decking boards differ; you have to consider the moisture level of the wood before leaving gaps between the boards. The gap size for the wood board should be between ¼ inch and ⅛  inch. As mentioned earlier, you have to consider how dry the wood is before deciding whether to leave gaps between them.

For instance, if you are using pressure-treated wood for your deckings, it is not recommended to leave gaps between the boards. Pressure-treated lumber has a high moisture content; if you leave gaps between the boards during installation when the board dries, the gaps between the boards will be too wide.

So it is recommended that you don’t leave gaps while installing pressure-treated wood deckings. The same principle goes with other wood types in that their moisture level is high. When laying your deckings, you can also work with a wood expert to assist you in knowing the spaces to leave between your decking.


The recommended size gap between decking boards should be between ¼ and ⅛ inch. When installing wood deckings, always consider the moisture content of the wood before deciding on particular gap size.


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