Impregnating a roof? Choose the right scaffold.

The wide Altrex RS TOWER 52 is the logical choice here. That frame spans 135 cm from upright to upright and the deck runs 245 cm long, and you use that room differently than on heavy work. You set a jerry can down in a drip tray, you lay the lance somewhere it will not roll off the edge, and you can walk past your own kit to the far end of the platform. With a fluid that creeps into everything, that last point is no luxury.

There is a second reason to hire wide. Impregnating is done with a lance or a low pressure sprayer aimed upwards at an angle, and that has you leaning further out than you are used to. A slim 75 cm frame may pass through a gate more easily, but it gives you less margin for that movement. If the only route round the back is a narrow path, that narrow model is what remains. Every width on offer is listed in the range of mobile scaffolds for hire.

What you do not need here is a scaffold that spans the entire roof. No such build exists in this hire fleet, and you would not want to pay for one either for a fluid you can put on in a day. You hire one tower and move it along the wall, serving a strip of roof each time. That pattern is what sets your number of rental days. If the width is still open, put the models beside each other using this survey of scaffold sizes.

On this job you do not measure to the gutter but as high as you can sensibly go. The further your deck rises above the roof edge, the more tiles the lance reaches from a single spot and the less often you have to reposition. For a house of two storeys that puts you on a reach of 8 to 12 metres. Working height means this: the height your deck sits at, plus the roughly 2 metres you get above it with a straight arm.

Start measuring at the ground under the castors, because that is the point the tower will actually stand on. A garden lying a step lower than the terrace changes the whole sum. Look at the pitch of your roof as well: on a steep surface the ridge sits much further from the edge than on a shallow one, and that decides how much you can still treat from the scaffold. The page about 12 metres of working height shows what such a build involves.

Choosing tight is extra annoying when impregnating. Stand low and you only get the bottom rows, so for the rest you still have to climb onto the roof or make another position. And because the fluid soaks in invisibly, afterwards you no longer know which row you did and which you did not. Booking a generous height is the cheapest insurance here. Working on a house with a roof at second floor level, go straight for the maximum.

Because this job takes you round the house, you look at all four sides in advance and not only at the front. The back often has the most room but the worst ground, while the front sits tight against the pavement. Walk the route you intend to move the tower along: can you wheel it in one piece, or is there a step, a fence or a terrace edge in between that forces you to take it apart and build it again?

More stays clear around the foot of the tower than the width of the frame, because the stabilisers stand out at an angle and have to land on something solid. Grass that goes soft after a shower is a real problem when impregnating, since you work in early spring or in autumn. Watch the planting too: shrubs along the wall push the tower away from the house. For a falling or loose path, the guidance on uneven terrain helps.

Think further about what goes on beneath you. Impregnating fluid running down the tiles ends up on your brickwork, your window frames and your planting, so cover what you do not want it to touch before the scaffold is in position. The neighbours' car on the drive and their open bedroom window belong in that consideration just as much. If the tower ends up standing partly on public ground, ask the council beforehand which rules apply in your particular neighbourhood.

Count on two to three rental days for an ordinary gable roof. Putting the fluid on goes quickly, but you move the tower often, and each shift costs you releasing brakes, drawing in stabilisers, wheeling, levelling and locking everything again. Add that up eight times or so and half a day has gone. On top of that the roof has to be clean and dry, so removing moss or a cleaning round asks for its own days beforehand.

Weather decides more here than your planning does. The fluid has to soak in without rain landing on it, and on a streaming wet roof putting it on makes no sense at all. Frost and fierce sun are both unhelpful. So do not pick a single day but a block of days that stay dry, and bear in mind that a week ahead you cannot make that choice reliably. To hire a mobile scaffold with a day of slack built in is not a luxury here.

That is why taking the period generously pays off. Only the first 24 hours count at the full amount; every rental day you put behind it gets 95 per cent off, so a margin of a day or two barely shows on your invoice. The other way round, booking tight is expensive: you stand with a half treated roof waiting for the collection van. A surface you skipped has to be gone over again the year after. To underpin that estimate, look at the article on rental days per job.

This is the heart of the job. The deck of the mobile scaffold measures 245 cm, and that is immediately the strip of roof you serve comfortably from one position. A long lance gets you a few rows of tiles higher, but the ridge of a steep roof is out of reach from the edge. For a wall of eight metres that means three to four positions per side, and on a house with four sides it mounts up nicely.

There are two ways to still do the top rows. Either you use a longer spray lance and accept that you work upwards from the edge, or you go onto the roof itself with the provisions that belong to that and use the scaffold only as an access and supply point. What does not work is reaching from the guard rail further than your arm allows. That is exactly the moment people lose their balance, and it saves you one reposition at most.

So work to a fixed pattern. Per position treat the full height you can manage, from the bottom row to as far as the lance goes, and mark where you stopped before you climb down. Because impregnating fluid soaks in colourless, a wet sheen is your only clue and it disappears. If you later also take on cleaning the roof tiles, keep to the same strips, so that both rounds follow one route past the house.

The tower comes to you as a set of loose parts, counted and complete, delivered on the spot you point out. Choose that spot with care: not in the middle of the path where your jerry cans and drip trays will stand, and not in the border you still have to cover. A bit of driveway or a corner of the terrace works best. Anything reserved before 15:00 on a working day is standing on your path the following working day.

You decide yourself which day it is brought and which day it goes again. When impregnating you would rather keep those dates open as late as possible, because you are waiting on a dry spell. Let the delivery fall the day before your first working day and the build is behind you before the weather turns. The survey of costs for delivery per province shows in advance where you stand, so that item never joins your rental price as a surprise.

As soon as you are finished we come and take the scaffold away again. Dismantling is yours, after which the parts stand complete on the same spot where they were delivered. Plan that dismantling for a dry morning, since wet tubes stack badly and slip through your hands. Rinse the tubes and the deck before you stack them, because dried impregnating fluid leaves marks on aluminium. Do not lay parts in the planting or you will be hunting a missing brace on collection day.

Load class 3 within EN 1004 puts a ceiling of 200 kilos per square metre on the deck under your boots. When impregnating that is no bottleneck, because a jerry can and a sprayer amount to little. The point is rather that a light load makes people careless: they climb with the lance in hand or lean over the rail because nothing heavy is aboard. What you carry up is light, but the height stays exactly the same.

The ordinary rules therefore hold in full. Lock the castors before you go up, never wheel the tower while somebody is on it or while your jerry can is still up there, and stop the moment the wind picks up. Wind is doubly awkward on this job: it pushes against the tower and it blows your mist across the garden, the windows and the neighbours' terrace. In stiff gusts you simply pause for an hour and pick up later in the day.

The particular risk here sits in the fluid itself. What soaks into a tile also lies on an aluminium deck and makes it slippery, so mop up spilt product straight away. Wear gloves and glasses, because you spray upwards at an angle and some of it always comes back. Keep the zone under the scaffold free of playing children and of pets, since what you spill lands there. Everything further that has been agreed sits in the rules that apply at height.