Thresholds are the most crossed and least protected part of any floor. Every trolley, barrow and suitcase in the building goes over them, they are a change of level by definition, and they are usually where two different floor finishes meet – which makes them structurally the awkward line in the whole installation.
Why thresholds fail first
Three reasons. They carry all the wheeled traffic, because they are the only way between rooms. They are a step, however small, so a wheel meets them as an impact rather than as a roll. And the transition strip itself – the metal or timber profile covering the joint between two finishes – is thin and it is usually fixed into one or both floors, so anything that moves it damages the floor around it.
Panels butted against a threshold crack
The common approach is to lay protection up to the threshold on both sides and accept the step. Two problems: the panel edge at the step gets hit by every wheel and chips, and the transition strip underneath is completely unprotected. Protection that stops at the threshold does not protect the threshold.
Ramp over it instead
The answer is a ramp: a tapered piece that goes over the threshold and restores a continuous surface, so wheels roll rather than strike. It needs a shallow enough gradient that a trolley will go over it without a shove, and it needs to be fixed so it does not slip. A ramped threshold transition is the single most useful protection item on a job with wheeled traffic and it is routinely left off the order.
What to do about the transition strip itself
The strip is usually the most fragile thing there and it is often the thing the client notices. A purpose-made channel cover that sits over the strip and takes the load onto the floors either side is the right detail. Where that is not available, a rigid panel spanning across, bearing on both floors and not on the strip, does most of the job.
External door thresholds
An external threshold carries water and grit in from outside as well as traffic. A ramp over it that seals against the floor traps that water and creates a slip hazard at the busiest point in the building. External thresholds want a draining detail – a ramp with a gap at the low side – rather than a sealed one.
Thresholds and doors that still have to close
A ramp over a threshold adds height at the door line, and some doors will not close over it. Check the door clearance before the ramp is made, particularly on fire doors, which cannot be propped open and cannot have their closers defeated. Where the clearance is not there, the answer is a shallower ramp on the low side only rather than a symmetrical one.
Thresholds that are already damaged
A scratched or dented transition strip is cheap to replace and disproportionately visible, because it is at eye level for anyone looking along a corridor. Where a strip is being replaced anyway, do it after the heavy trades rather than before, and protect the new one – a replacement strip damaged in week one is a wasted cost.
How to finish a run so the edge does not itself become the problem is covered in finishing the edge where floor protection stops.
What we can do
We make ramped threshold transitions and channel covers cut to the threshold width and height. Tell us what the two floors are, what is crossing and whether the door is external, and we will specify the ramp – including telling you when a simple tapered edge is enough because the traffic is foot only.