Installing a roof hook? Choose the right scaffold.

The model for this job is the Altrex RS52, the wide version at 135 cm that reaches up to 14.2 metres. At eight to twelve metres the size of the standing area counts for more than it does on low work: the taller the build, the more you notice that a wide foot gives less when you put force behind a screw up top. That steadiness is what you want at the moment you are holding a roof hook in place. The full range sits on the page with mobile scaffolds for hire.

The deck of 245 cm gets used differently here than on wall work. It is mainly your base: the roof ladder lies on it until you push it up the roof, your tool bag stands there, the roof hook and its screws are laid out ready, and there has to be room left for two people to pass each other. At 135 cm wide you can also crouch calmly at the edge while the other passes material up, which saves a lot of twisting when you line the plate up.

The narrow RS51 will reach the same height, but then you hand in that stable foot and have hardly any room to step across. A MiTower is out here in any case: it stops at 6.2 metres and is meant for working on your own, whereas roof hooks are a job for two. So do not confuse the model with the build; how high you go is something you choose when you hire, separately from the width.

Your measuring point here is not the hook itself but the roof edge where you step across. From there you walk up the roof, so the build need not reach the ridge. With the gutter of a two storey house at seven or eight metres, you land in the 8 to 12 metre class, with the deck between six and ten metres. On top of the platform height comes your own reach of roughly two metres, and that difference is exactly why the ridge may stay outside your build.

Look at the shape of the roof while you measure. A steep pitch puts the ridge far above the gutter, and then the distance you cover over the tiles is greater than the height you hire. A shallow roof brings the point closer. Measure as well how far the eaves project, because a wide overhang pushes the scaffold a good way off the wall, and that distance costs you height again at the moment you step across.

Choosing too tight punishes you immediately. Come out half a metre under the gutter edge and you have to pull yourself up to get onto the roof, and nobody wants to do that with a drill in the bag. Rather take the level where the top deck finishes flush with the gutter or a shade above it, so that you step straight across without hauling on anything. The page on twelve metres of reach shows what build that takes.

A build of ten metres makes stricter demands on the spot than a low one. The bearing area under the four feet is small and the load on each foot large, so you look for setts, paving slabs or a made up driveway, and not fresh topsoil or a newly laid grass path. A difference of a couple of centimetres between two slabs you correct at the bottom, because up top it works out into a lean you notice when you step onto the roof.

With roof hooks you often end up on the street side, because that is where the elevation with the most accessible roof lies. Talk to the neighbours about a parking bay and tell the council what part of the pavement gets taken. Keep all four stabilisers fully out; at this height that is not a luxury but the reason the build stays upright. How to deal with sloping or soft ground is set out in the guidance on stabilising.

Finally, look up before you start building. At this height sit the things that play no part in low work: the service cable into the house, a satellite dish, a tree hanging over the roof. Work out as well exactly where you want to come out at the roof edge, because that point fixes the standing position. If the roof hook belongs above a bay window, you set the scaffold a few metres to one side and climb diagonally up the tiles to where it goes.

The screwing is soon done; the rest is not. A build up to ten metres takes two people half a day, and taking it down takes another. In between sits the real work: lifting tiles, lining the plate up on the purlin or the boarding, fixing it and laying the roof watertight again. For a single roof hook you are finished within two hire days, and if several hooks go on different roof planes, count at least half a day extra for each plane.

What steers the planning is the weather. At ten metres it blows harder than at four, and wet tiles are no surface to walk on, so you want to be able to pick out a dry, still half day. Do not reserve exactly the days the work takes, then, but hire a margin in which that quiet half day falls somewhere. Losing a day to conditions is the rule rather than the exception on roof work, and certainly so in autumn.

Financially that need not stand in your way. The opening twenty four hours carries the cost of this hire; anyone who sticks days on after it sees very little added, thanks to the 95 per cent discount. A margin of two days therefore costs next to nothing, while having to hire again means putting a whole build like that up for a second time. More on judging a hire period for roof work is in this piece on hire days.

On this job you shift the build almost not at all. You build at the point where you want to get onto the roof, do your work there and take it down again. That makes the preparation more important than on jobs where you move along every two metres: anything you forget you fetch again from ten metres lower. Lay the roof hook, the right screws, the cordless machine, a spanner, a few replacement tiles and your roof ladder ready on the deck before the climb starts.

You step across from the top deck, not from an intermediate level. Push the roof ladder up over the tiles first and hook it over the ridge, then go yourself and have your tools passed up or hauled up in a bag. Never climb over the guard rail with loose items in your hands. On the deck of 245 cm there is room enough to work through that order calmly, even with two of you up there.

If two hooks are going in far apart, the question is whether you slide across the roof or move the build. Going over the roof is quicker as long as you can rehang the ladder; if the second hook lies on another roof plane, you dismantle and build again. Work that out beforehand, because it decides whether two days are enough when you hire. Replacing a few loose tiles fits into the same set up.

A set for ten metres consists of a fair number of parts: uprights, braces, decks and the stabilisers, all complete and counted on the docket. Reckon on a stack you cannot simply tuck into the hall, and point out in advance where it may lie without blocking the way to the front door. An order lodged by 15:00 on a working day sends the package your way the next working day; you name the drop off day and the collection day yourself.

Building it is your work, with the manual and the instruction video as your guide. If this is your first build this tall, allow a generous morning and do it with two of you: one passes up, the other builds from the inside. So let the drop off fall a day before your roof day, so that you are not building and fitting at the same moment. What the run to your province costs you can see under the charges per province.

At the end we take the mobile scaffold away again. You dismantle, stack the parts together by type and set them down where a van can pull up alongside without manoeuvring; we load it. Do that dismantling in daylight and not in the dusk after a long day on the roof, because the upper parts want passing down with attention. If a tile or a piece of tooling is still lying on a deck, take it off first.

The decks under you are made to EN 1004 in load class 3, which allows 200 kg of load on each square metre of deck. On roof hooks you go nowhere near that limit, because you take little up. What does count is the height: brake the castors before you step up, never move the build while somebody is on it or tools lie on a deck, and stop in a wind that has you bracing yourself up there. What the standard prescribes exactly is explained in the notes on this scaffold standard.

The most dangerous moment of this job is the step from the deck onto the tiles and the way back. Do it with empty hands, on a dry roof and with the roof ladder already hooked over. Do not walk loose across the tiles to have a quick look at something, not even when it seems only a metre. And bear in mind that the hook you are fitting is a safe anchor point only once it is fixed and the material around it has been made good.

Below you it has to stay empty. A tile you lift and put down for a moment slides away easily, and from ten metres it arrives with force. Fence off the zone around the foot with whatever you have: cones, tape or a car that can no longer get past. Warn the neighbours on the day itself, certainly if their driveway falls within that area, and do not work above a path people keep walking along.