Replacing window frames? Choose the right scaffold.

The RS51 with a deck width of 75 cm is usually the best pick from the fleet for this job. You set it tight against the brickwork, right beside the opening the new frame has to go into, and that works better with a narrow tower than a wide one. On replacement work there is also always material arriving: a pallet of frames, a skip for the old timber or a van that has to get near the wall. Look at the range on the page with mobile scaffolds out of the fleet.

Unlike decorating, what fits on the deck does count here. You have screws, anchors, packers, expanding foam, a sealant gun, a circular saw and a length of trim with you, and all of it has to fit beside two pairs of feet. The 245 cm of platform length gives you that room lengthways, with the tools laid at the upright side and the zone straight in front of the opening kept empty. That leaves working space around the frame itself, which saves a lot of shuffling while you level in.

If the frame sits in a wide elevation where brickwork has to be made good as well, or if three of you are at the same frame, the 135 cm wide RS52 is worth considering. For an ordinary house with a path down the side the narrow version still wins: it slips past the bay and through the gate to the back. As a model the RS51 reaches 14.2 metres of working height, so a frame on the top storey can be tackled with the same tower.

On this job you measure to above the head of the highest frame coming out. You have to get at the lintel, the brick course and the bit of pointing you close up again after levelling. For a first floor frame in an average house you land on a build reaching 6 to 8 metres. Those numbers come about because you add some 2 metres of reach to the platform height, so your deck lies at 4 to 6 metres.

Pick the build so that you can just reach the top and you have hired too tight. You want to be able to put the deck roughly at sill level, so the frame stands square in front of you, and then hang a platform higher to finish the head joint at eye level. So order one build more rather than one less, because half a metre short shows up exactly when the frame has to be levelled. The builds and their platform heights sit side by side at eight metres of working height.

Your tape starts at the ground the castors will stand on. A sunken lightwell, a sloping drive or a garden lying lower than the pavement changes your starting point and with it the build. Is the frame to be replaced in a second floor, then add a whole storey. Come out too low and you finish the head joint with your arms stretched, and that is exactly the seal that has to be watertight, or it leaks after the first heavy shower.

For this job the pitch involves more than the tower alone. Beside the scaffold you want a clear strip for the old frame coming down, for the new one still wrapped up and for the skip or trailer the waste timber goes into. The stabilisers take their own room splaying outwards, so count on a run along the wall that nobody has to pass through while you are busy. You keep that run free from the day you have the mobile scaffold delivered.

The ground counts double here, because a fair weight ends up on the deck. Setts, concrete or slabs carry that without trouble; fresh garden soil, a gravel bed or a newly laid drive sink under a loaded tower, and then your level no longer reads what it read an hour earlier. If the ground is not flat, use sole boards and check the setting again before you start measuring. There is more on that at setting up on sloping ground.

Think about the inside of the house as well. The old frame usually comes out inwards, and the new one often goes into the opening from inside, so the route through the room counts as much as the clear strip outside where the tower stands. So do not put the scaffold dead centre in front of the opening but slightly to one side, so you can guide from the deck while the frame can swing out past the upright.

Per frame, working in twos, you are busy about a day: measuring and preparing, taking the old frame out, levelling and fixing the new one, foaming and closing the outside joint. With three frames coming out you work towards three full days, and you do not want to plan those back to back without margin. So book the mobile scaffold from a day before the first strip-out, and keep a day of slack at the end of your hire period.

The waiting sits mainly in the finishing. Foam has to cure before you can trim it, sealant needs time before you may paint over it, and fresh pointing you leave alone until it has pulled in. Those hours run inside your hire period just the same. Rain is the biggest risk here, because an opened wall and a fresh seam do not go with a heavy shower. So plan the strip-out day in a dry window and keep a day in hand.

Those extra days hardly weigh in the cost. The full rate covers only the first 24 hours, and every following hire day is reduced by 95 per cent. Book tight and you run the risk of the scaffold being collected while the last joint has not been finished, and then you are balancing on a ladder over a half sealed seam after all. What hiring per model and per build comes to you will find including VAT at our rental prices, well before you undo the first screw.

A frame a metre and a half wide with double glazing in it soon weighs sixty to eighty kilos. You do not lift that over a guardrail, and you do not have to: the new frame nearly always goes into the opening from inside, while you guide, level and fix from the deck. Want to do it from outside anyway? Then take the glass out first and bring the frame up empty. Without glazing that halves the weight, and you feel it at once.

So you use the 245 cm deck mainly as a bench beside the opening. That is where the packers, anchors, screws, sealant gun and a piece of trim lie ready, and that is where the second person stands holding the frame in place while you read the level and adjust. Keep the strip straight in front of the opening empty, because the frame has to be able to tilt through there. Anything lying there is in exactly the wrong place when it matters.

Count on one pitch per frame and on more repositioning than you expect. You go along to measure, you stand there during the fitting and you come back for the sealing and the trim, so per frame you are on the same spot three times. Take the tools off the deck before you roll and lock the castors again afterwards. If decorating follows, painting the new frames joins onto this work seamlessly, from the very same pitches.

What reaches you from the fleet is a counted set of loose parts, out of which you build a tower yourself. Decide beforehand where that stack may end up and make sure the spot does not clash with the room for the new frame or the skip, because you will need all three at the same time. Order it on a working day, before the clock reaches 15:00, and your set stands on the drive the next working day, well ahead of the strip-out.

You pick the delivery date and the pick-up date, and on replacement work you deliberately set that delivery a day before the strip-out. You do not want to open the wall while the tower is still lying in parts on the grass. For the assembly put the manual and its video ready; two people have the tower up in half a day and can then check the existing opening size straight away. That way the strip-out day starts with a pitch already at the right height.

As soon as your hire period ends we come to collect the parts, once you have taken the tower apart and laid everything out complete. Do wait with that until sealant and pointing have had their time, because a tube scraping past a fresh seam pushes it straight out again and then that piece is yours to redo. Count the parts as you stack them and you know the set is right. The fixed transport costs for your province sit at the delivery rates.

Replacing a window frame is where the load capacity of the deck really comes into play. A platform may carry 200 kg per square metre, precisely what load class 3 within EN 1004 lays down, and with two adults, a box of tools and a piece of frame you are nearer to it than on any other frame job. Spread the weight over the full length instead of putting everything at the same upright, and bring material down as soon as you no longer need it.

The standing rules weigh heavier on this job than usual. Lock the castors before anyone climbs on, never move the tower with tools or people aboard, and stop work in a strong wind, certainly when a loose frame is standing on the deck catching the wind like a board. Check after every move that the four stabilisers make firm contact, because a loaded tower standing out of true you only notice once you are lifting.

The risks that belong specifically to this work come from below. What falls here is not a brush but a length of timber, a chisel or a shard of glass, and it lands on the path someone has just walked along. Cordon off the zone under the opening with tape or a warning sign, even when you are only off the scaffold for a moment. Work in gloves once glass is involved, and keep the deck clear of offcuts. The further rules stand at working at height and its rules.