Spider Crane Mats

On a construction site, ground protection is about bearing capacity — spreading a crane's point loads over soft or uneven ground so it does not rut, tip or sink. Spider cranes do plenty of that too, on made-up ground, in yards, on stripped subgrade around a building going up. But a large share of spider crane work happens somewhere altogether different — inside a finished building, on a polished concrete slab, across ceramic tile, over a timber floor, or in a period property with a stone floor nobody wants scored by a steel foot.

There the failure mode is not subsidence, it is a scratched, dented or cracked finish — and once that mark is there, no amount of engineering justification undoes it. Our aluminium construction spreads a leg's point load over a wider footprint, and that load spread keeps a finished floor unmarked just as reliably as it stops a soft verge rutting outdoors. Same physical principle, a very different failure to design out.

A spider crane's outriggers are not built like a mobile crane's. They sit narrower, closer to the machine body, with smaller individual feet — and because the crane crawls and re-picks its way around a room or a floor plate, there are usually more mat positions to plan across a job than there are on a single mobile crane set-up. That points to several separate small mat positions rather than one large configuration under four widely splayed beams.

It also means getting the mats through the same doorway, stairwell or goods lift the crane itself used. This is where the smaller end of our range earns its keep, because it is handleable in the most literal sense. Our Mini modules, at 580 x 580mm and 13kg, and our Short modules, at 1160 x 580mm and 25kg, both fit through a standard doorway carried under one arm, and both lay out in seconds under a foot that might only stand there twenty minutes before the crane crawls a couple of metres and resets for the next pick.

Here we want to be plain, because it is a safety point and not a marketing one. A mat under a spider crane's foot reduces the point pressure on whatever is directly beneath it — that is real, and it is useful — but a mat has no say in what a suspended floor, a mezzanine deck or an upper-storey slab can carry as a structure.

That is a question for whoever designed or has assessed the floor, and it needs answering before the crane goes up in the lift, not while it is stood on the fourth floor mid-pick. Any work above ground level — a roof terrace, a completed floor plate, a multi-storey car park deck — means someone qualified checks the crane's setup position and reaction loads against that structure's actual capacity first. Our mats protect the surface finish and even out contact pressure on whatever is there. They do not replace that structural sign-off, and nobody should treat them as if they do.

Anywhere tight enough to need a spider crane in the first place is rarely a site with a telehandler standing by to shift ground protection about. We build ALIMATS to be carried by two people with no lifting equipment at all — no heavy plant needed — and that counts for more here than almost anywhere else in the crane mat world. The same lobby, stairwell or lift that took the crane in is what the mats have to go through too, one or two at a time, repositioned every time the crane crawls to its next pick point.

It is the sort of practical detail that decides a job — a heavy timber mat and a narrow stairwell do not mix. It is also why we inspect, clean and check every ALIMATS mat before it goes back out on hire. A mat that is going to be carried by hand into a finished building needs to arrive looking the part, not scuffed from a previous week on a muddy compound.

Our ALIMATS system is rated up to 80 tonnes SWL and builds out to configurations of 8.07m2 for the genuinely heavy end of the crane world — none of which a spider crane will ever trouble. What matters for this application is that the same patented aluminium system, in its smaller Mini and Short configurations, comfortably covers the loads a mini crane's legs put down, with every SWL figure independently checked by a Fellow of the Institution of Structural Engineers.

So there is no case for kitting out a spider crane job with mats sized for a heavy-lift crawler. The job is to pick the right module for the floor and the doorway, not the biggest number on the spec sheet. We hire mats and configurations by the day, week or long-term, or sell them outright, and we deliver across the UK 24/7 for the jobs that come together at short notice.