Floor Joists & Timber Floor Structures

Often, yes, though not always a structural one. Bounce can come from undersized or over-spanned joists, noggins missing between them, a joist that has cracked or lost bearing at one end, or simply chipboard decking that was never glued and screwed properly. A creak is more often a fixing or decking issue than a structural one. We assess the floor in person — lifting a board where needed — before saying which it is, rather than guessing from a description.

No, and we would be doing you a disservice if we did. Joist size, spacing and permitted span are read from published span tables (TRADA or equivalent) for the exact timber grade, species and loading involved, or taken from a structural engineer’s calculation where the span or load is unusual. The same visible joist dimension can be correct in one house and inadequate in another depending on spacing and what the floor carries. We confirm the figure for your specific job rather than quoting a rule of thumb.

In most cases, yes. New floor structures and most joist replacement or strengthening work fall under Building Regulations Part A (Structure) and are inspected by the local authority or an approved inspector before the floor is decked over and covered. We leave the joists accessible for that inspection and build to whatever the engineer’s specification requires.

The common causes are a span that was borderline to start with, a later addition of load the joist was never sized for — a cast-iron bath, a stud wall built directly on top of it, a loft conversion turning a ceiling joist into a floor joist — or timber decay from a long-term leak or damp source. We look at which of these applies before recommending a repair, because sistering a joist solves an undersized-span problem but does nothing for one that is rotten at the bearing end.

Sistering means fixing a new timber alongside an existing joist to add strength, rather than replacing the joist outright. It works well where the existing joist is sound but undersized or has a localised weakness, and it is usually quicker and less disruptive than a full replacement. It is the wrong repair where the original joist has rotted, cracked through, or lost its bearing — in those cases the damaged section needs cutting out and a new structural member fitting, sized to the specification rather than matched to a joist that has already failed.

We fit proper joist hangers wherever a joist meets a beam, wall plate or another joist, rather than relying on skew nailing, which is weaker and not acceptable for most new structural work. Hanger type and fixing pattern follow the manufacturer’s specification for the load involved. Skew-nailed older floors are common in period Berkshire properties, and whether to upgrade them to hangers during other floor work is something we flag rather than assume.

Yes, but it needs a structural engineer’s input first. Adding a bath, a shower enclosure, or a new stud wall onto an existing floor changes the load the joists underneath are carrying, and whether the existing structure can simply take that load — or needs sistering, additional joists, or a different strengthening approach — is a calculation, not something read off by eye. We build to that calculation once it exists.

We carry out floor joist and timber floor structure work across Berkshire, Surrey and South Buckinghamshire, including Ascot, Bracknell, Windsor, Maidenhead, Reading, Wokingham, Sunningdale, Virginia Water, Camberley, Stoke Poges and Gerrards Cross.