A Graceful Spliced Repair to a Structural Joist

In a lot of cases, yes — a splice repair, bolting a new section of timber alongside the sound part of the existing joist, restores full strength without the cost and disruption of replacing the whole span. Full replacement is reserved for joists with damage running most of their length, widespread rot, or where access makes a splice impractical. A site visit tells you which category your floor falls into.

The usual causes are long-term overloading beyond what the joist was sized for, a notch or hole cut into it at some point for pipework or cabling that weakened it, historic water damage leading to rot or decay, or simply age combined with the natural drying and movement of timber over decades. A split is often the timber telling you it has been asked to do more than it was designed for.

We temporarily support the floor with adjustable props before any cutting begins, transferring the load away from the damaged section for the duration of the work. Depending on the extent of the damage and the room involved, the floor may need to be kept clear during the repair itself, but this is confirmed with you in advance so there are no surprises on the day.

It depends on the extent and location of the damage. A straightforward, localised splice repair that restores a joist to its original strength is often carried out without additional sign-off, but where the damage is extensive, the joist carries an unusual load, or the property has specific constraints, we will recommend a structural engineer's input before proceeding. We would rather flag that early than cut corners on a structural repair.

We assess how far the damage extends along the joist, how much sound timber remains either side of it, and whether there is enough undamaged length to fit a splice that overlaps well beyond the weakened section. If the damage is too extensive, or there isn't enough solid timber to splice into, we recommend replacing the joist instead rather than forcing a repair that wouldn't be fully sound.

Once the floor is propped and the damaged section cut away, a new length of timber matched to the depth and width of the original joist is fitted alongside the sound remaining timber, overlapping it by a good margin either side of where the damage was. The two are then bolted together through the overlap — sometimes with timber or steel splice plates for extra strength — so the old and new timber act as one continuous structural member.

The splice itself sits within the floor void, so once flooring, ceiling boards or any other finishes are reinstated, there is nothing to see from inside the room. If the repair is being carried out from below — in a cellar or exposed ceiling void, for example — the splice remains visible there, but it is finished neatly and squared off rather than left looking makeshift.

Yes — all structural repair work is covered by our standard workmanship guarantee, confirmed in writing as part of your quote. Structural work is exactly the kind of job where that assurance matters most, and we stand behind it.