Floor runners are the tanalised timbers that the flooring is nailed to. The standard quantity is already included; extra runners are an upgrade rather than a requirement for ordinary use.
Compare standard runners with extra runners
These two shed bases make the difference easier to see. The 12x6 image shows the standard runner arrangement without the extra-runner option, while the 8x6 image shows the additional supporting runners fitted beneath the floor.
When to consider them:Add extra runners if you plan to store exceptionally heavy items and want to increase support beneath the floor.
