The sub floor is a layer of flooring under the top surface flooring on a narrowboat. It is important to use good quality materials to avoid future problems on your narrow boat.

Narrowboat sub floor is a layer of flooring under the final floor
A sub floor is placed over the ballast on a narrow boat, before the final flooring is fitted.
Narrowboat sub floor in place in preparation for final floor covering to be laid.

Sub Floor… What is it?

Sub floors are laid over the cabin bilge after ballast has been placed. With the timber boards subject to changes in temperature, air flow and humidity try to use the best quality material you can.

They are usually 18mm marine grade ply to BS 1088 EN 636-2 and EN 314-2 Class 2 or above.

It is good practise to ensure adequate ventilation and to cut a rear access hatch for bilge inspection.

The sub-floor is fitted onto timber batons which are screwed onto the steel framework above the base-plate. This needs to be really solidly fixed. If there is any movement or creaking in the sub-floor, this will be transferred through to the final floor covering. Use good quality fixings and pilot drill and counter sink holes.

18mm exterior grade ply is recommended. We would recommend a minimum of Class 2 grade timber, with Class 3 being the optimum. Better quality timber and glue systems are used in the construction of Class 2 and 3 plywood and therefore it is less likely to  develop soft spots in high usage areas.

If you are fitting out your narrow boat, you can have some real fun with planning and design. Use tape to plan out rooms and design living spaces. There’s no need to be too accurate with measurements at this stage, just free-style your design. Marker paint can be obtained from all good tool suppliers and use this to mark positions of lights, sockets, radiators, pumps etc. Basically anything that needs to be hung or considered before you line out can be marked. Alternatively you may of already used our Design Service to professionally design your layout which you can then use to mark out each area.

Sub Floors

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