Installing ventilation? Choose the right scaffold.

For a sleeve at loft level you hire the Altrex RS52, a wide tower on a 135 cm frame. That width is not indulgence. A core drill stand already claims half a square metre of decking, a bucket of water sits beside it, and there is usually a second person working the motor while you watch the stand stay true. Three things like that will not sit side by side on a 75 cm tower. The other widths and build heights sit in the overview of towers available for hire.

The RS52 comes in several builds and for this work you take the one giving 8 to 12 metres of working height. A room scaffold is meant for indoor jobs and drops away at once; a one person tower is not reckoned for two people with heavy kit between them. Something else counts too: a 135 cm frame will not pass a ninety centimetre garden gate. Walk the route before you book, from the kerb to the patch where the build has to stand.

The platform is 245 cm long and that decides whether two sleeves come off a single position. If intake and extract sit within that length of one another, you cut them in turn and save yourself a move. Lie further apart, which with a ventilation system is more often the case than not, and you plan for two standing positions. Measure that distance on your drawing before you commit to a build, because it is worth half a working day.

Start indoors. Hang the unit where it is going to live, set out the duct run and see where that run touches the outer wall. That point is your drilling point and it nearly always sits higher than people expect: with a unit in the loft you come out in the gable or just under the roof edge, and on a two storey house that is soon eight to ten metres above the street. A thin pilot hole from inside finds it again from the deck.

Take the measurement from the ground under the tower and not from your front doorstep. Working height, in the way you book it, is deck height with something like 2 metres of arm and shoulder added on top, yet a core cut uses none of that reach: the stand belongs against the wall at chest level, so you lay the deck about a metre below the drilling point. Keep that in mind when you pick a build, because half a metre too high works as badly as half a metre too low.

Choosing too tight is expensive here. A core cut you have to make with your arms stretched above your head runs off line, and a crooked duct through a cavity wall never comes straight again. Fitting the facade hood afterwards also asks that you stand square to it. Take the build that clears the drilling point comfortably, even if the deck ends up a rung higher than strictly needed. What such a position gives you is described at a working height of ten metres.

The tower has to stand directly under the drilling point. A core drill stand is either bolted to the wall or braced between the deck and a stand tube, and that only works when you are square in front of it. A position two metres to one side is no alternative here. So look at what lies on the ground in that spot: with a gable it is often a side path, a strip of gravel along the boundary or the piece of pavement where the bins live.

The RS52 measures 135 cm across the frame and with the outriggers out the base wants another half metre on every side. Reckon on a clear lane of well over two metres holding nothing at all, where every one of the four base plates comes down flat and level. Watch for drain covers, for a basement light and for the lip of a drive that falls away to the road. If the ground drops, see how to take that up on an uneven surface beneath a tower.

Core drilling brings water with it and that water runs down the wall. Put a bucket under the drilling point, lay a sheet over whatever stands below and expect the slurry to mark paving. If the tower takes part of the pavement, tell your neighbours and keep a strip open for people to pass. What is allowed on the footway is worth asking the council about a week beforehand rather than on the morning itself.

The work outside is short; the work around it is not. Before the scaffold earns its keep the duct run has to be in and the unit hung, and those are one or two days you do without a tower. Then comes the core cut, half an hour to an hour per sleeve, and after that the hood goes on and gets sealed. All together you land on three to five hire days, depending on the number of sleeves and the thickness of the wall.

Inside those days sit waiting times you cannot hurry. Sealant round a facade hood has to cure before rain touches it, and a cavity wall you have just opened is better left a day to dry before you close the hood over it. Rain or a stiff wind pushes the drilling back. So set your collection date a day or two beyond the day you hope to be finished, rather than on it, and the last morning stays calm.

Booking with room to spare barely shows in the total. Only the opening twenty four hours count at the whole rate; from your second hire day onwards 95 per cent is taken off, so a reserve day held back for poor weather weighs nothing against a second delivery run. What this build costs is set out on the page with the rate per model. With a tower this size that weighs all the heavier, because raising it and stripping it is work you carry out yourself.

The core cut is the moment the width of the deck pays for itself. You set the stand down, bring it plumb, connect the water hose and let the barrel feed in slowly. Meanwhile someone has to be able to stand at the motor without treading on the other one's feet. On a floor of 135 by 245 cm that is comfortable; on a narrow tower you would be shuffling round each other with a turning drill in your hands.

Bear in mind that the core comes out of the wall as a solid cylinder of stone. On a wall of thirty centimetres that is a few kilos, and you do not want it dropping outwards. Catch it, lay it on the deck and leave it there until you go down yourself. Work steadily as well, because a barrel that binds gives a jolt through the stand, and you feel that jolt right through the build under your feet.

When you mark out, think about short circuiting the air. If the sleeve for fresh air and the one for stale air sit too close together, the system draws its own exhaust back in and works against itself all year round. Keep them well apart and preferably not in the same lee. That is precisely why two standing positions are so often the answer rather than one. Fix that second spot before you settle the build height, because the second hole sometimes sits half a metre lower.

You pick your own delivery date and collection date when you book. An order finished before 15:00 on any working day goes out to you the working day after that. When installing ventilation, let the scaffold come on the day the indoor work is finished and not sooner, because a tower standing unused in front of your house for a week eats hire days for nothing. Line the delivery up with a spell of calm weather too, since a core cut in driving rain gains you nothing.

A build of this size reaches you as a sizeable pile of separate parts, counted through in full before it leaves the depot. Work out ahead of the delivery day where such a stack can lie for four days or so without blocking anything; a drive, a garage or the side of a path all work. Bear in mind that you carry a good many more pieces than on a low tower, so drop the stack as close as you can to the assembly spot and keep a barrow handy.

Raising it falls to you, with the manual to hand and the video on the site. We do not come and assemble, and we do not deliver a standing tower. At 8 to 12 metres of working height this is no job on your own either: work with two people, build one lift at a time from the deck you are standing on, and fit the outriggers before you climb higher. Afterwards we take the set away again on the date in your reservation.

At this height the load rating genuinely matters. Every deck we hire out answers to EN 1004 within load class 3, so 200 kg is the most that may stand on a square metre. Add up what stands on it during a core cut: two people, a stand, a motor, a bucket of water and a cylinder of stone. That comes closer to the limit than painting ever does, so take up only what you need at that moment and leave the rest on the ground.

Lock the castors as soon as the tower is on its spot and check them again before the drill starts, because a turning barrel puts sideways force into the build. Never move the tower with anyone on it or tools left up top; at this height repositioning is work for two people and an empty deck in any case. In a strong wind you do not go up: ten metres against a gable carries far more wind than you notice at street level.

Keep an eye on what is happening below you as well. Ventilation work sends down pieces of stone, sealant and tools, and water runs the wall besides. Tape off the ground under the tower and keep children and visitors away while the drill is turning. Wear eye protection and gloves throughout, even though it looks like no more than a single hole in a wall. On a wet deck with a film of slurry across it you lose your footing a good deal sooner than you would think.