03 Extensions on a building that cannot shut

Adding floor area to a working building is mostly an outside job, which sounds easier than a fit-out and usually is not. The dig, the deliveries and the crane are all on the side of the building your customers and your staff use.

The work we take on is single-storey: a rear or side extension to a shop or workshop, an infill between two existing wings, a covered loading area, a new store or office built off an existing wall. Up to the tie-in, almost none of it touches the inside of the premises. The tie-in is the part that does, and it is the part the whole programme is arranged around.

03.1 Before a spade goes in

The first week is paperwork and searches, and skipping it is how a mini-digger finds an electricity main. Before the dig we want:

• Statutory undertakers’ plans for the area of the dig, and a cable and service scan across it.
• The engineer’s foundation drawing, and the design for any underpinning or temporary support it calls for.
• Written confirmation of where plant may stand, where spoil may be stockpiled, and for how long.
• The planning decision and the building control appointment, both made by the client.
• Agreement on the access route for a wagon and a digger, with the hours it may use it.

If the dig is near a boundary, the neighbour conversation starts here and not when the digger arrives. We do not run that conversation for you, but we will put the dates and the method in writing so you have something to show.

03.2 Digging beside a building that is full of people

Excavation runs to the engineer’s drawing, in the sequence the drawing gives, and the depth is not our decision. What is our decision is how the hole behaves while it is open: it is battered or supported, edge-protected, covered or fenced at the end of every shift, and it is never left open across a weekend next to a public route.

Spoil goes straight onto a wagon where the yard allows it, because a stockpile beside a fire exit is worse than an extra haulage movement. Concrete pours are booked for the start of a shift so the pump is off the access route before your deliveries arrive. The groundworker and the digger driver are our own, which is why the dig and the drainage connections do not sit waiting on a third party’s diary.

03.3 Shell, roof and getting it dry

Blockwork and frame go up off the finished slab, then the roof, then the windows and the external door. The target from the start of this stage is one thing: weathertight. Until the new structure is dry and lockable, everything inside it waits, the programme is at the mercy of the forecast, and materials have to be kept in the yard rather than on site.

Scaffold comes with its own design and handover sheet and is inspected on the interval the hire requires; the inspection record stays in the file on site. Where the scaffold or an edge of the works is over a route your customers use, that route is diverted and signed before the scaffold goes up, not after.

03.4 The tie-in, and the week it costs you

The tie-in is the opening cut through the old external wall into the new space. It is the one stage of an extension that is identical to a structural alteration, and it is run that way: temporary works to the engineer’s drawing, the opening formed, the beam set and fire-protected, and nothing struck until the engineer signs it off.

This is the week you feel. The area inside the old wall comes out of use, a screen line goes up across it, and the breaking goes in the out-of-hours window. We fix the tie-in week on the programme early and we do not float it, because you have staff rotas and deliveries to arrange around it. Everything before it is arranged so that when the wall is opened the new space is already dry, lit, floored and ready to be walked into.

03.5 Deliveries, plant and your service yard

An extension turns your yard into our compound for the duration, so the compound is drawn out on the same plan as the works: where the store and the welfare unit sit, where the skip stands, which bays stay yours, and which gate the wagons use. Deliveries are booked into the windows you give us and are banked at the yard in Rochdale when a window is missed, rather than left on your yard overnight.

Plant is kept to what the stage needs and goes back when the stage ends. Fuel and small plant are locked down nightly. At the end of the job the compound is cleared, the surface is made good and the yard is swept before the final walk-round, which is done with you on the date the programme gives.