How high can a mobile scaffold be?

Two limits set the maximum height

The first limit is the equipment itself. Every mobile scaffold comes with an assembly instruction stating, per configuration, how high you may stack and which parts belong where. That instruction is not optional: it describes the structure as it was tested, down to which braces, platforms and stabilisers belong on which level. Deviate from it and what stands there is no longer what was tested.

The second limit is the place the tower stands. Outdoors in wind along an open facade you can go less far than indoors in an enclosed hall, and on soft grass less far than on paving. Those two limits work side by side: the lower of the two is the height you keep to that day, whatever the brochure says.

In practice the question usually comes the other way round. People know how high they have to work and want to know whether that is allowed. So start at the work point, calculate back to the platform height and then check whether that set-up can be made safe on your site with the parts supplied. If it cannot, a lower set-up with a different work sequence is almost always the answer.

Key facts

Working height is platform height plus two metres

The platform height is the height of the floor you stand on. The working height is the height you can still reach, calculated as platform height plus two metres, the reach of an adult. A platform at six metres therefore gives a working height of eight metres. Do not mix the two up, because a two metre difference is exactly enough to order a tower that just fails to reach the gutter.

Manufacturers and hire companies almost always quote working height, because that is the figure a customer can use. During assembly you work with platform heights instead, because that is what you stack. So for every figure you come across, keep in mind which of the two is meant. The explanation with worked examples is in dimensions and sizes. Ask which figure is meant whenever a quote or a page leaves it open.

Measure your work point as high as you actually need to be, not the ridge of the roof. For a gutter that is the underside of the gutter, for window frames the top rail, for solar panels the place the top bracket goes. Subtract two metres and you have the platform height to order. On working height you can see which set-up belongs to each metre.

The range runs from 4.2 to 14.2 metres

Our mobile scaffolds cover working heights from 4.2 to 14.2 metres. At the bottom end that puts you at a low extension or a garage, at the top end well above the gutter of a three storey house. Everything in between is a matter of how many levels you stack, using the same types of parts. Which step suits your job is shown on the pages per metre, for instance 8 metres or 12 metres.

The MiTower is the exception: a one person scaffold up to six metres working height. Above that you are looking at the RS51 at 75 centimetres wide or the RS52 at 135 centimetres, both with a platform length of 245 centimetres. Width says nothing about maximum height, but plenty about how much room you have on the platform and how wide the base is.

If you need more than 14.2 metres working height, the mobile scaffold range ends and you move to a fixed facade scaffold erected by a scaffolding company. That trade off is described in hiring a tower or having a scaffold built and in mobile scaffold or facade scaffold. Up to that limit you keep working with the same parts and the same method, which makes moving along a facade a good deal simpler.

The assembly instruction decides, not your judgement

Our equipment comes from Altrex and is built to EN 1004, the European standard for mobile access towers. Part of that standard is that an assembly instruction is supplied setting out the order, the parts required and the permitted assembly heights. That instruction is the answer to how high you may go: it applies to the configuration in front of you, with the stabilisers that come with it. What else the standard covers is in EN 1004 explained.

Load class 3 belongs to the same story: 200 kilos per square metre of platform. That figure does not change as you build higher, but the consequences of an out of level tower or overloading do grow with height. Spread the weight and leave heavy materials on the ground until you need them. Loading and weight takes that further. Bear in mind too that your load grows as the job progresses.

Keep the instruction with the scaffold during the job, not in the van. You need it just as much for dismantling as for assembly, because you work in reverse order and the stabilisers come off last. The full sequence is in assembling a mobile scaffold. Keep it dry, for instance under a board in the van, so it is still readable at the end of the week.

Indoors you can usually go higher than outdoors

The biggest difference between indoors and outdoors is wind. Indoors the air is still, so there is no sideways force on the tower and no gust running along a facade tugging at sheeting. A higher assembly is therefore sooner justified indoors than outdoors with the same configuration, and stabilisers come into play sooner outdoors than in. That is why the same tower behaves so differently in a hall and on an open corner.

Indoors, other limits take their place. Ceiling height is the hard one, and the floor has to carry the wheel pressure without damage or deflection. In a stairwell or above a stairwell opening the legs rarely stand at the same level either, which calls for a separate set-up. Using a scaffold indoors and setting up over a stairwell cover that.

Outdoors the shape of the building counts as well as the wind. An open corner, a gap between two houses or a detached facade on a dike catches far more wind than a sheltered back garden. So look not only at the forecast but at the site itself, because the same wind force feels completely different at two addresses. If you stand on the corner of two streets, expect gusts from changing directions.

Stabilisers widen the base

A mobile scaffold is narrow compared with its height, so stability comes from the area it stands on. Stabilisers are the angled supports you push out at the bottom to widen that area. From a certain assembly height the instruction prescribes them, and they are supplied with the scaffold. Extend them until they touch the ground, and check that they actually carry load.

Set them out symmetrically. Four stabilisers extended equally give an even base, while a set shortened on one side gives the tower a preferred direction to tip in. If a stabiliser cannot come out fully because of a wall or a planter, move the scaffold rather than shortening the stabiliser. Check them again once the sun has moved the paving or after a downpour.

• All four stabilisers are extended and touching the ground
• The tower stands level, checked in two directions
• The wheel brakes are on and the spindles are locked
• Diagonal braces are on every level as the instruction shows
• Guardrails and toe boards are fitted all around the working level
• The platform hatch closes and stays closed while you work

Tying in to the facade on higher set-ups

Above a certain height, and certainly for work along a facade, you secure the tower to the building. Tying in means coupling the scaffold to fixed points so that wind cannot move it. Where those points go and how you space them depends on the height and on what the facade allows. Stabilising and tying in describes the options. Plan the tie positions before you start stacking, not once the tower is up.

A tied scaffold is not something you simply roll along. To reach the next bay you release the ties, move the tower and secure it again in its new position. That costs time, which is exactly why it pays to decide in advance how many bays you split the facade into. A platform length of 245 centimetres saves a move per facade width there.

The ground sets a limit of its own

How high you can responsibly build also depends on what is under the wheels. Paving, concrete and asphalt carry the point load of the castors fine. Grass, sand and freshly turned soil do not: a wheel sinks in, the tower goes out of level and it loses exactly the flat base it needs. Base pads spread that load over a larger area.

On sloping ground, a driveway or a pavement with a fall, you level the tower with the spindles before building any higher. Correcting halfway up is no longer possible without dismantling. After a shower of rain, check that the wheels have not sunk in after all, and repeat that check at every move. Uneven ground works through the situations. A tower that starts out of level only gets worse with every level you add.

Watch what is under the paving too. A manhole cover, a cellar hatch or a freshly laid slab cannot always take the load, and you only notice once the tower is up. In that case put the leg half a metre further along or shift the load to a firmer point, even if that means an extra move during the job.

From platform height to working height in a table

The sum stays the same at every height: platform height plus two metres. The table below converts a number of common platform heights into the matching working height, so you can see at a glance which step suits your work point. The last column gives an example of the kind of work point at that height. The figures assume an adult of average height working with arms raised.

Use the table as a conversion and not as an order form. Which set-up you finally need depends, besides the height, on the width you can accommodate and on the room for stabilisers. If you fall between two steps, take the higher one: standing on your toes to just reach the gutter is exactly where things go wrong. Add the height of anything you have to stand on the platform with, such as a mortar tub.

Moving a tall tower is done under control

Moving a tall tower is the moment most things go wrong. The platform has to be empty, nobody may be standing on it and loose parts come off before you push. Push against the frames at the bottom rather than high up, and only roll over flat, paved ground free of thresholds, cables and manhole rims. Work with two people where you can, so someone watches the route ahead.

At greater heights and over longer distances, dismantling to a lower level is often quicker and safer than wrestling with a full tower. That sounds long winded, but the parts unclip without tools and you are back up within minutes. After every move, run the whole check again: brakes on, level, stabilisers out, braces complete. Allow a couple of minutes per level you take off and put back.

• Platform empty, nobody on the tower, tools taken down
• Sweep the route in advance and clear thresholds or cables
• Push at the bottom, never pull from the platform
• Take the stabilisers along and extend them again afterwards
• Re-level the tower and lock the wheels once it is in place

Wind, rain and frost decide the day

As wind increases, height is the first thing to come down. Stop working as soon as you feel the tower move or find it hard to keep your balance, and leave the platform empty. If the wind keeps up, dismantle to a lower level or completely, because an empty but tall tower stays sensitive to gusts. Secure or lay flat any materials standing at the foot of the tower as well.

Rain and frost mainly affect the platform and the rungs. Wet aluminium is slippery, and in frost a thin layer of ice can sit on it that you only feel once you are standing there. Dry the platform before you start and climb calmly, with both hands on the rungs. Hiring a scaffold in winter goes further into working at low temperatures.

Do not leave the scaffold standing with materials on it between working days. Paint, tools and sheeting are the things that come down in an overnight shower or gust. An empty platform with the hatch closed is the standard at the end of the day, even if you carry straight on the next morning. Take sheeting and covers right off in that case.

Ordering the right height and having it delivered

Order before 15:00 and the scaffold is delivered the next working day, anywhere in the Netherlands. Delivery and collection sit in a fixed amount per province, listed on delivery costs. Collecting yourself is free and by appointment at Zeeburgerpad 89 in Amsterdam, provided you have transport that takes parts of 245 centimetres. Book the collection when you order, so you do not have to chase it later.

The first hire day is charged at the full daily rate and every following day costs 5 percent of that daily rate, so planning a few extra days is rarely an expensive choice on high work. What your set-up costs is calculated by the configurator on prices, with the explanation on mobile scaffold hire costs. The deposit is 500 euro on delivery of an RS51 or RS52 and 1000 euro if you collect it yourself.

If you are torn between two heights, or unsure what your site allows, send a photo of the facade via WhatsApp with the height of your work point. We will say which set-up fits and what to watch out for. To read on, the other guides are in the knowledge base and the practical questions are on frequently asked questions.