Insulating a roof edge? Choose the right scaffold.

For this insulation work you take the RS52, the roomier Altrex model whose deck measures 135 centimetres. You need that width because the job stays in one place for a long stretch. A roll of insulation material, a foam gun, sealant cartridges, a knife and a short saw all want to be within arm's reach at once, and on a cramped deck you shuffle those things about all day. What else is available sits together on our page about the mobile scaffold range, with the sizes and possible builds per version.

At a roof edge you are seldom up there on your own, either. Opening up and closing again goes a good deal faster with two people: one fills the strip, the other passes up the finishing pieces and catches the offcuts. On 135 centimetres you fit side by side without anyone having to step back each time. That saves a quarter of an hour per setup, and reckoned across twelve setups you win back half a day on your hire period.

The slim 75 centimetre model only comes into the picture here when you have to reach the back through a gate under a metre wide. Weigh that honestly: you win that one passage, but you give up working room at every standing place on the whole round. If you can carry the parts round the house, choose the roomier version. Both widths sit side by side in the explanation of scaffold sizes. Measure that gate at its narrowest point, between the hinges and not between the posts.

The measuring point for this job sits lower than for roof maintenance in general. You do not need to go to the ridge, and not even to the row of tiles, only to the line where the roof plane and the facade touch. On an ordinary terraced house of two storeys that line sits somewhere between six and ten metres, which lands you on a build reaching 8 to 12 metres. Start measuring at the level where the castors will stand; a sloping drive counts in that sum.

Then work back to the deck. On top of the height at which that deck hangs comes roughly 2 metres of reach, and it is that sum you enter as the working height when you book. With roof edge insulation you would rather turn the sum around. You do not want the transition above your head but straight in front of you, so look for the build that leaves the deck half a metre under the rim. That way you look into the cavity opening instead of at it, which spares your neck.

Choosing too low punishes you harder on this work than on painting. Foam and sealant applied above your head with straight arms drop back into your face and bond poorly, and a joint you cannot see is a joint you never check. Hiring one extra build section is quickly arranged; a badly sealed cold bridge is something you repair years later. If you are torn between two builds at a roof edge on the second storey, take the higher one.

The cold bridge runs right round, so your standing places run round with it. That means a different surface on each side of the house. At the front the castors rest on block paving, at the side on a narrow path that falls away towards the boundary, at the back on slabs that sink into the sand beneath them after a shower. Walk that round once with a spirit level in your hand, so you know in advance which corner wants a base plate or a thick plank.

At the foot the four stabilisers claim their space on every side, and along a facade that is exactly where things are in the way. A downpipe with a shoe under it, an outside tap, a crawl hatch, a row of planters and the hedge the neighbours have let grow up to the boundary. Clear that away before the set arrives, because a stabiliser you can only half extend does not count. Differences in level you take up as described for a tower on uneven ground.

One more detail weighs heavily on this job: the overhang. If your roof projects half a metre past the facade, you cannot get the setup tight against the wall and your deck stands some way out. Measure that projection from the ground beforehand, because it decides whether you still reach the cavity opening comfortably. With a substantial overhang, put the build a section higher rather than half a metre nearer. That single measurement often settles which reach you end up hiring.

An average mid terrace has thirty to forty metres of roof edge; on a corner house or a detached one that soon runs to double. Per setup you finish a little over two metres, and per setup you are three quarters of an hour busy with opening up, filling, sealing and closing again. Add the moving to that and you land on three to four days for an ordinary house. That is the period you reserve, not the number of hours in which you actually gun foam.

Those days contain interruptions you cannot compress. Foam has to expand and cure before you trim it, sealant needs to skin over before the cover batten goes on, and on a wet facade you do not start at all because the material will not take. A dry, still morning is worth more on this work than a full day with showers. So tune your planning to the forecast and not to the Saturday that happens to suit you.

Booking generously is cheap with us. The whole rate covers the opening 24 hours, after which a reduction of 95 per cent lands on each further hire day. Sticking a spare day on the end of your planning therefore costs you almost nothing, while stopping halfway with an open rim can leave you with a wet cavity. What a longer period means is set out under hiring by the day or by the week, and the rental price for each build stands on the price page, all including VAT.

A deck 245 centimetres long decides exactly how much roof edge you take on per setup. That sounds like little, but it is a pleasant unit to think in: you open a stretch, insulate it, close it again and only then move on. That way there is never more than two and a half metres of rim lying open at the moment it unexpectedly starts to rain. Work from corner to corner and not at random, and you keep an overview.

Take up per setup what you are certain to use and nothing more: the insulation for that strip, the foam gun, sealant, a knife, your rule and a small bucket for waste. Anything missing up top costs you a climb of eight metres and a broken run of work. Cut the material to length below, because sawing on the deck produces dust, loose pieces that blow away and a messy surface you have to stand on yourself. A bucket with a lid keeps that waste together.

What people misjudge are the corners and the interruptions. At every corner of the house, at the downpipe, at a dormer and at the junction with the neighbours the straight line stops and the fitting and measuring begins. Reckon on half an hour extra per interruption and on a setup you have to place slightly differently. If you combine this with painting the roof overhang, do that afterwards, because putting paint over a fresh cover batten is quicker than working the other way round.

You get the mobile scaffold supplied as loose parts, complete and counted beforehand. Point out a place where that stack may go: preferably on the drive or on a patch of grass you will not be using this week, and certainly not directly under the roof edge you are about to start on. Put your order through before 15:00 on a working day and the next working day is your delivery day. Both the bringing date and the collection date are yours to choose.

Putting the setup up belongs to your part of the job. A manual comes with the set, and the instruction video shows exactly in what order the parts go together; with two people the first build costs you half a day. Moving it after that goes far faster, because you wheel the whole build to the next corner in one piece. So do not start insulating on the day the parts arrive, and try to plan the delivery just before a dry spell.

When you are finished you take the build apart and lay everything within reach of our driver; the collecting we arrange after that. Keep the count as you dismantle, so you do not discover afterwards that a brace is still lying behind the hedge. Which amount goes with bringing and returning in your own province is set out clearly under the costs per province, so you can budget that alongside your hire days from the start.

If the two of you stand still in one place with a roll of insulation, a toolbox and a bucket of waste between you, the load approaches the limit sooner than you would think. That limit lies at 200 kg per square metre, laid down in EN 1004 as load class 3, and it applies per bay and not per tower. So spread your things along the length instead of putting everything by the access hatch. More on this under load and weight.

The ordinary rules of course still stand. Castors braked before anyone goes up, no moving at all while there is still a person or material on top, and in strong wind you stop work. With roof edge insulation something specific comes on top of that: you push and wrestle against the rim to get the material into place, and you feel that sideways force back in the build. Go back along all four stabilisers each time you have shifted position.

The risks that really belong to this job sit in the small things. Cured foam makes a deck slippery, offcuts blow in all directions, a knife you cut towards yourself with sits at the height of your colleague's face, and torn out old insulation or a rotten length of batten drops straight down. Keep the strip under the build clear and put a wheelbarrow or a cone there. Everything else that applies is described under working at height and the rules for it.