Replacing a ventilation grille? Choose the right scaffold.

For grille work on a house the RS51 is the size to take: a tower 75 cm wide out of the Altrex programme. Narrow is no compromise here but a gain, because the route to the front elevation runs past a hedge and a bike rack, and round the back through a gate as well. A tower of three quarters of a metre you take to the next window on your own without first clearing half the garden path. Which widths and heights stand ready is shown by the list of towers we hire out.

You need very little deck area for this errand. Beside your feet lie a cordless drill, a box of screws, a trimming knife, a tube of sealant and the new profile, and that is the entire inventory for the day. What matters more is being able to turn on the spot with a grille a metre and a half long in your hands without catching it on anything. Extra deck width does nothing for that, though it does bring you a stack of heavier parts that somebody has to carry to the back first.

The wide RS52 at 135 cm only becomes attractive when two people work a whole elevation together and a supply of profiles goes up with them. If the item to be swapped is indoors instead, above a stairwell or in a partition, outdoor work does not arise and you take a room scaffold from our hire range, which still passes an interior door from about 70 cm. For a row of windows outside, the narrow version stays quickest, simply because you move it more often than you stand on it.

On this errand the top reference point is neither a gutter nor a ridge, but the head of the highest frame that holds a ventilation grille. That is what you measure to, and on an ordinary family house that head falls within a reach of 6 to 8 metres. Of that figure roughly two metres is the reach above the deck; the rest is the platform height you state when you book. What such a build means in practice is set out under eight metres of reach.

The zero point of that measurement lies under the castors and not at your front door. If the front garden falls away towards the pavement, if there is a basement window below, or if the tower stands behind the house on a sunken terrace, you begin half a metre to a metre lower than you had it on paper and hire one section more. Where the top frame sits under an overhang or right beside a dormer, check at once that your head and a lifted profile still clear it.

When replacing a ventilation grille, standing too low punishes itself immediately. Come out with your eyes below the head and you cannot see the clips lying in the rebate, so you lever by feel right beside a sealed unit. You also end up working with straight arms above your head, exactly the posture in which a profile shoots out of your fingers. For frames on a second storey take one section more than you think; in the hire it makes little odds and it saves half a day of irritation.

The tower belongs square under the frame, with the deck a shade above the head so that you can look down into the rebate. Under the castors belongs a flat, closed surface: paving slabs, block paving or the asphalt of a drive. A border that gives way beneath a wheel after rain will not do, and neither will a freshly filled strip of soil along the foundation. The four extendable supports at the base ask more room on each side than the tower itself takes up.

What gets in the way on this errand is almost always directly under a window. That means a low hedge along the front, a row of planters on the sill, the outside tap, a bike rack and the downpipe on the corner where you now need to put a support. Move those things away before the scaffold parts arrive, because steering an assembled tower between obstacles costs you more time than freeing two ventilation grilles put together does.

If the footway falls away towards the gutter you correct it with the adjustable feet and check with a spirit level that the standards really are vertical; how that goes is described at working on ground that is not level. If the tower ends up with two legs on the footway, keep a path open for pedestrians and check with the council what the rules are in your particular street. Such things you arrange beforehand rather than on the morning of your first window.

Per window, replacing a ventilation grille takes about three quarters of an hour of freeing, fitting, fixing and sealing, and that is for a profile which comes away without surprises. Shifting to the next opening adds a quarter of an hour every time: brakes off, supports in, roll, line up and lock everything again. Four to six grilles on the top storey will fill a working day at that pace. So here you think in days that the tower stands there and not in the number of screws you turn.

Two days is a sensible reservation for an average house. Day one goes on assembly and the front; day two on the rear and the dismantling. If a profile jams in the rebate, if a size turns out to have been ordered wrong or if a piece of rotten head timber has to be made good first, you genuinely need that second day. The weather has a say as well, because a sealant joint goes onto dry timber and never onto a clammy head.

Booking on the generous side costs you almost nothing here. In the way the hire is worked out, only the first day counts at the whole rate; each further day arrives with 95 per cent knocked off it. Adding a spare day is therefore better value than stopping halfway along the rear elevation because the van is already pulling up with a window half open. How long a job needs is set out in this piece on the length of a hire period.

Look carefully first at what sits in the head, because the fixing differs by type. A glass grille clamps with springs between the pane and the rebate and shows no screw at all from outside. A surface model is screwed through a flange onto the frame timber and does show those heads. An acoustic box, finally, is let into the head and has a separate flap on the inside. From the deck you see that distinction in seconds; from the ground you are simply guessing.

Then the worn profile has to come out without your touching the edge of the glass. Cut the sealant joint through over its full length with a fresh blade, press the clip springs in one by one and draw the profile square towards you. What you never do is put a chisel or a screwdriver between profile and pane to lever with: that is where the butyl edge of a sealed unit tears or the pane goes altogether. That controlled pull is only possible with both feet still on the deck of the tower you hired.

A deck of 245 cm covers one window opening in practice plus a little margin towards the corners of the frame, and there it stops. At a wide screen or a made up frame arrangement you shift once more halfway along. So take everything up in one round: the new profile, the screws, the sealant, a cloth and a narrow nozzle for the rebate. Every forgotten accessory means climbing down and up again, and over six windows that weighs more than the errand itself.

What is delivered to you is a countable stack of separate parts, complete but flat, and not a finished tower. Decide beforehand where that stack may lie, preferably on the drive or on a strip of grass beside the house and certainly not right under the window you want to start on next morning. If your order is settled before 15:00 on a weekday, everything heads your way the next working day, so the delivery can safely fall the day before your start.

Assembly is your task, and on this errand it is not much of one, because you build once and after that only roll. With two people you are about an hour and a half at it; the manual supplied and the video explain each step in the right order. Do not put that build on the same morning that you begin replacing a ventilation grille, because then you start precise work with arms that have just lifted twenty scaffold parts, and you feel it at the first clip spring.

You pick an arrival day for the parts yourself when you reserve, and a day on which they disappear again. Afterwards we pull up to fetch everything; you strip the tower and lay every part back complete on the spot where they were unloaded. What that driving to and fro costs depends on your province, and the figures stand with VAT included at the rates for delivery. Take that into your budget before you fix a date for good.

Load class 3 under EN 1004 is what the whole hire fleet is built to, and it permits 200 kg on a square metre of decking. For replacing a ventilation grille that is far more than you ever draw on: you, a tool bag and three profiles together come nowhere near the limit. Do run the sum anyway once somebody climbs up with you to pass a long profile. What else the standard settles is set out in this note on the scaffold standard.

For the rest, the fixed habits of this trade simply apply. Set the wheel brakes before anyone climbs, keep the deck empty of people and tools whenever the tower is on the move, and come down as soon as the wind rises enough to twist a loose profile out of your hand. After every move, walk round the four supports and feel whether the brakes have truly bitten before your boot touches the first rung again. Two seconds of checking is cheaper than a tower that shifts under you halfway up.

The particular danger of this errand lies in the glass and in what can fall. A profile pulled free has sharp cut ends, screws roll off a deck without warning, and under a front window there is often the footway where people walk past. Put a tray or a traffic cone down there and keep that strip of pavement empty for as long as you are busy with a frame. Everything else that applies is gathered at the rules that apply at height.