04 Openings, props and temporary works

Taking a wall out of a building that is standing up is a sequencing problem with a very short list of allowable orders. The order comes off a drawing. Our job is to follow it exactly, in the hours the premises can give up, without putting dust or risk into the part that is still trading.

04.1 Who designs it and who builds it

On a structural job there are three sets of hands and the boundaries between them matter more than anything else on this page.

1. The client’s structural engineer designs the permanent work and the temporary works, issues the drawings and calculations, inspects at the hold points and gives written permission before props are struck.
2. Building control is appointed by the client and inspects on its own schedule. We give it access and we work to the notices it leaves, but we do not instruct it and we do not answer for it.
3. This team builds what the drawings say, in the sequence they say, and keeps the records: delivery tickets for the steel, the propping arrangement as installed, monitoring readings, inspection sign-offs and photographs before anything is covered up.

If a drawing cannot be built as drawn — a bearing that lands on something the survey missed, a padstone that will not fit the wall as found — work stops at that point and the engineer is telephoned the same hour. We do not substitute a detail. That is the single rule that keeps this kind of work honest.

04.2 The sequence of an opening

The shape is the same whether it is a shop wall or a tie-in to an extension, and only the detail changes.

1. The area below and, where there is a floor over, the area above are cleared of stock and fittings and taken out of use. A screen line goes up across the trading side.
2. Finishes come off the wall so the structure can be seen and compared with the survey. Anything that differs from the drawing is photographed and sent to the engineer before the next step.
3. Temporary support goes in to the engineer’s arrangement: props on spreaders over a sound bearing, needles through where the drawing calls for them, and the arrangement recorded as installed.
4. The engineer inspects the temporary works. Nothing is cut until that inspection is signed.
5. The opening is cut, the beam is lifted in, set on its bearings and packed, and the connections made as drawn.
6. The engineer inspects again and gives written permission to strike. Props come out in the order the drawing gives, not in the order they are in the way.
7. Fire protection, fire stopping and make-good follow, each photographed before it is covered.

04.3 What propping looks like on site

Temporary works are the part of this job the client sees least and the part that takes the most of our time. Props are set plumb, on spreaders, over a load path the drawing has already settled; they are pinned, not jacked past the drawing; and the arrangement is photographed and recorded on a propping sheet that stays on site with the drawing it came from.

Nobody adjusts a prop because it is in the way of a trade. Nobody takes one out to get a board past. If the arrangement obstructs the work, the work waits and the engineer is asked for an alternative arrangement in writing. Props are checked at the start of every shift by the site agent and the check is initialled on the sheet.

04.4 Monitoring, and the reasons we stop

Where the engineer’s drawing calls for monitoring, we install the targets or gauges it specifies and record readings at the interval it sets, on paper, on site, with the time and the initials of whoever took them. The readings are sent to the engineer at the frequency asked for and not held until the end of the stage.

Work stops and the engineer is called when a reading moves beyond what the drawing allows; when a crack appears, lengthens or opens; when the structure as opened up differs from the survey; when water is found in a bearing; or when anyone on the team says they are not happy with the support. The last one needs no further justification and costs nobody their place on the job.

04.5 The hours it happens in, and the floor below

Breaking out an opening is the loudest and dirtiest hour of any job we do, so it goes in the out-of-hours window and the premises is told which night it is on, in writing, before the week starts. Cutting is water-suppressed or on extraction, the screen line is checked before the first cut, and the trading side is swept and damp-wiped before the doors open the next morning.

Where there is an occupied unit or a basement below the works, the bay beneath is taken out of use for the duration of the propping and the strike, not just on the night of the cut. That is usually the hardest thing we ask of a commercial client, and it is not negotiable while a temporary arrangement is holding a load that a wall used to hold.

How the dates, the keys and the possession windows are set is on programme and possession, and the plant we keep for this work is listed on the yard at Rochdale.