Removing algae? Choose the right scaffold.

For algae on a tall wall we advise the wide Altrex RS TOWER 52, with a deck of 135 cm. That width is not a luxury here but the whole point: on a narrow deck everything you bring up stands in the same wet strip where you put your feet. At 135 cm you keep a dry side free for the bucket, the jerrycan and your phone. How the builds differ in width and reach you compare on the page where you hire a mobile scaffold.

The deck is 245 cm long, so each standing position puts a good two metres of wall within reach. On a wet job the combined measurement counts: along those 245 cm you walk back and forth, while the 135 cm of width lets you step past your bucket without treading in it. That sounds small, but on a wall ten metres high it saves you dozens of balancing acts with a full container in your hand.

You hire the narrow RS51 at 75 cm only when the wall cannot be reached any other way, through a gate or an alley for instance. You give up working room and will leave the bucket below more often. Narrower still exists, but the RS44 room scaffold reaches 3 to 4 metres and never comes near a roof edge, since it is meant for indoor work. For a wall full of growth the wide build is nearly always the better hire.

Algae usually sit thickest on the top few metres, where the wall stays wet longest and catches the least sun. Your highest working point is therefore often the edge under the gutter, not halfway up. On a house of three storeys that brings you to 8 to 12 metres of working height. Your platform then stands between 6 and 10 metres, because working height is the height of that platform with about 2 metres of reach added.

Start your measurement at the paving under the wheels and stop at the underside of the gutter. If a boxed gutter or an overhang projects, count its depth as well, because you have to get under it at an angle with a pole. Working below a gable end, the surface to be cleaned often carries on a few metres above the gutter, and that costs a whole storey in what you hire. The matching build is described on the page about twelve metres of working height.

Hiring too low shows on the top edge. What you clean from a distance with a pole never gets rinsed properly, and that is exactly where the growth stays. You also end up working with the lance pointing upwards, so the water runs in at your sleeve and spreads across the deck. Choose the build that puts the top edge at eye level, and for a third storey those heights are set out at the third floor.

On wet work the standing position matters more than on any other job, because you are soaking the ground under your own wheels. Put the setup on paving, block or concrete and not on grass or loose soil, which turns to mud after half a day of rinsing. If the water runs towards your feet, lay a channel of boards or steer it to the drain with a sheet. A wheel sinking while you stand at ten metres is exactly what you do not want.

Around the base the four stabilisers have to swing out fully, and on a build of 8 to 12 metres those feet stand further out than on a low setup in a garden. Clear that strip completely: bikes, planters, the water butt and the garden furniture, and keep free the hose you will need at the tap. Cover the planting under the wall before you start, because cleaner running down lands there whatever you do.

Think about what happens beyond your own boundary too. Wash water with growth in it runs across the pavement and can creep under a neighbour's shed door, and a car parked within ten metres catches the mist. Warn the neighbours and start on the side where the water can drain away, so you do not flood your own working area. How to put a tall setup down firm and level is in the piece on stabilising and anchoring.

For a wall of three storeys reckon on four to seven rental days. The sum is simple: each position covers a good two metres of width over the full height, so a wall ten metres wide already asks four to five positions. Every position means moving, levelling again and checking the stabilisers, and at this height that takes half an hour each time. Two elevations or a corner house nearly doubles that, and then you are talking about a full working week.

On top of that come waiting times you cannot compress. Algae cleaner has to soak in before you brush or rinse, and depending on the product that takes a quarter of an hour to a couple of hours. A north facing wall then dries slowly, and in frost or fierce sun you do not work at all. So reckon per position with applying, soaking, brushing and rinsing, and not with the minutes the spraying itself takes.

Do this in one unbroken period. You settle the full rate for day one, and on all the days that follow you get 95% off, which makes leaving it standing for a week far cheaper than ordering the tower twice for a few days. Dismantling and rebuilding also costs you two half days, and on a tall wall that is exactly the work you can do without. How to judge the period is in the piece on rental days.

Work each position from the top down, because everything you put on runs that way. Start at the gutter, let the cleaner soak, brush it, then rinse down in the same lane. Finish that strip of 245 cm completely before you move the tower, or you get drying marks where two positions meet. That seam you put on a corner, a downpipe or a vertical joint, where nobody looks for it once the wall is dry.

What you take up is heavier here than on paintwork. A ten litre bucket weighs ten kilos, and there is a brush on a pole, a spray lance and a hose running up from below. Take the water hose up on the outside and clip it loosely to the guardrail, so no weight hangs from your wrist and nothing slides under a wheel. Put your bucket on the dry half of the platform, out of the walking line.

Before you roll, everything comes off the deck and the hose comes loose. You never move a mobile scaffold with materials or a person on it, and on a wet floor you do not want to ride along yourself. Look where the water has run before you release the wheels, because a slippery slab under a wheel makes steering awkward. If you are cleaning the gutter from the same position that week, plan it straight afterwards.

What arrives at your front door is a stack of loose tubes, frames and platforms, complete and counted. Point out beforehand where that stack may lie, and bear in mind the water you will later send down the wall, because parts in the rinsing zone are already in the mud on build day. Confirm it on a working day ahead of 15:00 and the load leaves the depot the next working day, so you can jump on a dry forecast at short notice.

You choose the arrival date and the departure date yourself. For this job you choose a start when it stays dry and calm for a few days, since you do not want to build ten metres of tower in the rain. Assembling is your own job, with two people and from the bottom up, with the manual and the instruction video to hand. Allow half a day before the first litre of water hits the wall. For a tall build the step by step build guide is no luxury.

Dismantling belongs on your side of the deal too: you take the build apart and lay the parts ready, after which we take them away again. Rinse the tubes and the platforms clean before they go on the stack, because dried algae and cleaner barely come off later. Count out loud while you take it apart, so no brace stays behind under a shrub. What the run out and back costs depends on your province and is listed under delivery and collection charges.

The mobile scaffolds we hire out are built to EN 1004 and sit in load class 3, where 200 kg is allowed on every square metre of deck. Wet work fills that space faster than you would think, because two people, a full bucket, a jerrycan of cleaner and a hose full of water all add up. Spread that weight over the platform instead of gathering it at one guardrail. What the classification means in practice is set out in the note on the standard.

A few things are fixed and you do not deviate from them. The wheels are braked before you put your weight on the first rung, nobody rides up while the setup is moving, and in strong wind you do not step on at all. At twelve metres you feel a gust sooner than at four, and wet clothing chills you quickly in the meantime. Walk round all four feet after every new position, certainly when the ground has become soaked.

The danger that belongs to this job sits under your shoes. A deck with cleaning water on it is slippery as soap, so cover it with anti slip matting or stiff cardboard and swap that layer as soon as it starts to shine. Wear boots with a coarse tread. Keep cables and power tools out of the water and close off the strip below, because a lance or bucket falling ten metres hits whatever stands there. The remaining rules are at the rules for working at height.