Friday, 11 February 2011

You Can't Legislate For Loonies

Despite the best efforts of the Health & Safety Executive to encourage safe working practices you simply can't legislate for the 'loonies' out there - like this pair of roofers photographed on a mobile phone by a friend of mine in Bury St Edmunds the other day.

There are two guys working on a house roof. The ladder that is laid on the roof is not a proper roof-ladder with a hook to go over ridge to keep it in place. Neither ladder has been made fast in any way. The one on the roof is being kept in place by the second guy standing on the upright ladder holding onto it with his hands and transferring the load through his body down the stiles of the ladder he is stood on to the ground below.

  • If the upright ladder is not secured at the foot to prevent it slipping (which it isn't) then it could easily loose grip under the load, even in dry conditions.
  • Even if the upright ladder was well bedded into the ground or tied so that the foot cannot slip the combined weight of two men plus ladder bearing down on it may well be close to the designed maximum for the ladder rungs to bear.
  • If the upright ladder is at the optimum safe angle of 75 degrees it may not allow the man standing on it to exert enough upward thrust to support the man on the roof without propelling himself backwards (with or without the ladder he is stood on).
  • If the man on the roof misses his footing (easy to do as the roof tiles prevent him getting more than just his toes on to the ladder rungs) the result will be like a 'domino derby'
I should add that they have put a pair of 'ladder mitts' (see review below) on the bottom of the roof-ladder stiles. I'm not sure if this is:
(a) to protect the roof tiles from cracking at the point of maximum load when the guy steps from one ladder to the other.
(b) to protect the ribs of the guy standing on the upright ladder or
(c) to protect the foot of the ladder itself when it does come crashing down to the ground!

Thursday, 10 February 2011

The Five P's Rule

Have you come across the "Five P's Rule"?

- Proper Planning Prevents Poor Performance

Many times accidents with ladders happen because someone fails to think through the full implications of what they are doing. As a consequence they don't foresee potential pitfalls and plan appropriately to avoid them.

Here is a story I heard recently about a man who needed to carry out some work on the roof of his house.

Concerned about the risk of falling off the roof he came up with a cunning plan. He found a piece of rope strong enough to hold his weight and long enough to reach right over the ridge of the roof down to the ground on the other side; where he tied it to the towing hitch of his car, which was parked on the front driveway.

Climbing to the top of his ladder at the back of the house, he tied the other end of the rope around his waist so that he had enough slack to move about on the roof but, if he did slip, his fall would be arrested before he went over the edge.

Everything was going well until..........

.......the moment his wife came out of the house, got in the car and drove away!

I don't know if this story is really true but it demonstrates the point. The ensuing accident would not have happened if the man had thought things through a bit further: if he had taken away his wife's car keys and stuck a warning sign on the steering wheel - or maybe just told her what he was about to do!

Tuesday, 21 December 2010

Ladda Limpets Reviewed

It was a ladder slipping on a frosty paving slab two years ago that set me on a quest to find a decent ladder safety device that was quick to deploy and effective in the widest range of situations.

Most of the safety devices on the market work on the principle of friction - having a large rubber base that improves grip by increasing the surface area in contact with the ground. I've tried a couple of these and, generally, they work pretty well but the problem is that when you need them most - on slippery ground - is the time they are at their least effective (car tyres are made of hi-grip rubber but they still skid on ice, loose gravel or grease). Some other ladder safety devices work by having a sharp point or blade that penetrates the ground (I even invented one myself). They work very well - but only if you have a ground surface that is penetrable whilst being firm enough to offer adequate resistance to slipping - no good at all on concrete!

Laddatec Limited's 'Ladda Limpets' work on a totally different principle - that of triangulation; the two clip on legs forming a rigid triangle between the ladder stiles, the legs and the ground, which greatly reduces the chances of the ladder sliding away from the wall. Because of the method used the Ladda Limpets will improve safety on any surface, even if it is a bit unstable or slippery like loose gravel or wet decking. It also doesn't matter if the surfaces that the Limpet's feet rest upon are at different heights to where the feet of the ladder are stood (e.g. steps - see photo). All that matters is that the surface is firm enough to take the weight. I decided to give them a try.
Ladda Limpet deployed on some slimy steps shows how triangulation works.
The 'shop' button on Laddatec's own website doesn't seem to work but there are a number of online retailers offering Ladda Limpets with prices ranging from just under £40 (on special offer -including p&p) to about £85 - against an RRP of £70! For a professional trades person like me I don't consider that too expensive, but the price might put off a few DIY ladder users. Oddly when I searched the web for them I had to spell it 'Ladder Limpet' rather than the spelling used by the manufacturer - even then only a couple of results came up and I had to search under the more general terms of 'ladder accessories' and 'ladder safety' before finding the best deals.
The kit comes fully assembled and ready to use, apart from adjusting to fit individual ladders as per the simple instruction sheet. The strong metal legs attach to the ladder by means of a pair of tough plastic, asymmetric and tapered, T shaped pegs or "Support Pins" that hook around the stiles before sliding down until the rubber feet hit the ground; that's it - job done and ready to climb.
An added benefit is that the splay of the Ladda Limpet legs is such that it just about doubles the width of the ladder base, thereby reducing the risk of the ladder falling sideways.
Adjusting the limpets for different sizes of ladder is quite straight forward but it takes a few minutes to get it right. The Support Pins pegs are held in place by cotter pins (like the pins that hold pedals on to a bicycle). Slackening the nuts on the cotter pins (with the little plastic spanner supplied in the kit) allows the pins to be removed and rotated to suit the thickness of the ladder stile whilst the depth to which the pins are inserted into the legs can be varied depending on the width of the stile.

Asymmetric 'Support Pins' hook on to ladder stiles - fit is adjusted by slackening cotter pins(note missing yellow trim insert on rear support pin - see below)

Outside view of Limpet head showing cotter pin nuts and the shape of ends of support pins,
which are designed to fit a variety of ladder sizes (note again missing yellow trim ).
I found that although adjustment is quite easy it takes a bit of fiddling to achieve the best fit. As a window cleaner I use two different sizes of ladder, swapping between them frequently as the needs of the job in hand dictate.
Unfortunately swapping the ladder limpets from one ladder to the other is not so simple as it entails adjusting the stile width setting every time. As a consequence I did not bother fitting the little plastic protective covers for the cotter pin nuts because that just added more fiddle (and more delay) to the process. In use I also found that the neat little pieces of yellow plastic trim fell out of the ends of the support pins very quickly and I soon discarded them.

In practice, following a few days of continually re-adjusting the support pins (including some minutes fumbling in my pockets trying to find the elusive spanner) I opted for setting the pins at a position which would enable the Ladda Limpets to be a tight fit on the big ladder and a bit of a loose fit on the smaller one without adjustment. CAUTION - this is NOT recommended by the manufacturers who suggest the gap between the edge of the pins and the stile should be no more than about 1mm, however I will then spend too much of my day messing about with a spanner and not enough actually earning any money. A simple solution would be for the nuts on the cotter pins to be replaced by some sort of quick release catch - just like on the pedals of modern racing cycles.
Despite these minor aggravations I have found the Ladda Limpets very easy to use and, once adjusted, quick to deploy. They definitely have improved my safety working at height in difficult conditions, including some very slimy concrete steps and frosty paving slabs and they do give the ladder a very secure 'feel', which gives me extra confidence as I climb.
Thanks to a clever design of both the attachment pins and the rubber feet they can even allow for a range of variations in the angle that the ladder is leant at (although normal safety criteria still apply).
I decided to see how far I could push this when I needed to access a Velux window set in a pitched roofed single storey extension, which calls for me to use a stand-off bracket at the top of my ladder resting on the roof just below the window and deploying the ladder at an angle of about 45 degrees - way outside normal safety tolerances! In the past I have secured the ladder by attaching a stout cord to a strong point on the ground and tied to the bottom rung. Just to be on the safe side I tied the foot of the ladder in with the cord as usual but just left enough slack to give the Ladda Limpets a chance to prove their worth first.

As the photo below shows the Limpets were at a steeper angle to the ground than the ladder itself. All was well until I was about 2/3 of the way up but then the foot of the ladder began to slide and the back up cord went tight- the triangulation angle was not enough in this situation.
I tried a similar experiment in a different location, where I would estimate the ladder angle was about 60 degrees or so and it worked fine.

Ladda Limpets used at less than the optimum angle - but BEWARE !!!!
This is NOT recommended practice.
Ladda Limpets definitely reduce the chance of a ladder slipping provided that it is deployed at something around the optimum angle of 75 degrees - even on wet, greasy, loose or icy surfaces. They will accommodate shallower angles of lean whist still offering better grip than many friction type devices but there is a limit, which I would suggest is in the region of 60-65 degrees; however I would never recommend doing this without a back up security system in place.
Unfortunately the method of attachment means that you cannot leave the Ladda Limpets installed permanently on the ladder (unless you adjust them up very tightly - which make it difficult when encountering uneven ground or where a less than perfect ladder angled is necessary). Instead you have to remove and refit every time that the ladder is moved.

The instruction leaflet suggests that the Limpets are taken off the ladder by reversing the fitting process but in practice I found that, for me, the simplest thing was to return the ladder to the vertical position, which caused the limpets to slide gently down to the ground where they remained when I picked the ladder up to move it to the next window.

At about 2kg the Ladda Limpets are not too heavy to carry around but, as they can't remain attached to the ladder it means going back to pick them up or trying to carry a ladder one handed. I think I might try joining the two limpets together with a length of cord to enable me to hang them over my shoulder for easier carrying - as the plastic trims have fallen out of the ends of the support pins I can can pass the cord through the hollow pins and just knot the end. It's a shame they don't have some sort of handle or a means of making them stay in place on the ladder for carrying.

  • This is a great bit of kit for the professional ladder user - definitely the best ladder safety device I have tried to date - and I recommend them highly. But normal ladder safety considerations must still not be forgotten!!
  • They would be a lot better if fitted with a quick release catch on the cotter pins to make it quicker and easier to swap between ladders. Some sort of built in carry-handle / loop would be helpful too. Because of this I only use my Ladda Limpets when I feel I really need to instead of every time I climb.
  • Ladda Limpets work on any hard surface even if it is wet, slippery or loose like gravel. Indoors they won't damage floor coverings.
  • They won't work where the surrounding surfaces are soft (like a small fish pond cleverly situated close to one of my customer's houses!) or where space around the base of the ladder is too restricted, perhaps by shrubs or other objects close to the foot of the ladder, which prevent the legs being fitted.
  • If space around the ladder is limited fitting just one Ladda Limpet still offers better climbing safety than none.
  • The splay of the Ladda Limpet legs considerably helps improve sideways stability too - very important if the top of the ladder is resting against a slippery surface like UPVC fascias or in windy conditions.
  • The yellow plastic trims are a total waste and not worth bothering with - discard them.

here is a link to a Youtube video about the Ladda Limpets which shows how they work in more detail.

Additional information from the manufacturers website

Sunday, 19 December 2010

Christmas Capers

Some friends of mine in the USA put this manikin up outside their house for a bit of a joke last Christmas but the joke backfired a bit when several passers by thought it was for real.
One motorist nearly crashed his car stopping as quickly as possible and running to assist the stranded climber!

Still it stands as a salutary reminder to everyone putting up Christmas lights and decorations -please take care - it's so easy to succumb to the temptation to just stretch out that last inch or two rather than to descend and move the ladder again.

Hospital food may have improved in recent years but maybe you'd still prefer to have your Christmas dinner at home - so safe climbing and a happy Christmas to you all.

Tuesday, 30 November 2010

Ladder Mitts Review

A number of manufacturers offer rubber protectors for the top of ladders to prevent damage to window sills and reduce the risk of the ladder slipping sideways. But just how good are these so called, 'Ladder Mitts'?

I put a pair to the test using a 4 metre 'Lyte' 2 stage aluminium extension ladder with an 83kg load on the fourth rung from the top - equivalent to a typical working situation for a window cleaner. Unfortunately the window sill was not quite high enough to achieve the optimum ladder angle of 75% but was close enough to give reasonably satisfactory results. To test the grip I attached a spring balance to the top of the stile and, climbing a second ladder, exerted a sideways pull until the test ladder moved towards me.

Without the Ladder Mitts on it the aluminium ladder was moved easily with a sideways force of just 6 kg. making horrible grey marks along the edge of the sill as it did so.

With the rubber Ladder Mitts fitted the ladder required a force of 11kg to be applied to it before any sideways movement took place and without marking the sill at all. Without Mitts the top of the ladder had moved about 5cm, with the Mitts the movement was only about 1cm before it gripped again - clearly much improved.

I repeated the test on brickwork. Without Mitts the ladder displaced sideways at 9kg and 18kg with Mitts fitted.

As well as protecting UPVC window sills and cladding the Ladder |Mitts greatly increase grip on other surfaces like brick. The higher you go the greater the risk of the ladder being blown sideways in strong winds so it makes sense to use them here too, especially as the working height increases for jobs like gutter clearing and fascia painting.

I have actually used a pair of these things myself for several years and always thought they were pretty good, now I know the facts I wouldn't lean a ladder against a sill or UPVC cladding without them. They definitely do prevent damage and increase safety. A number of my customers, who have previously had their window sills and frames damaged by other window cleaners that don't use Mitts, have been pleased to see the extra care I take with their property and commented accordingly.

Available at around £10-£14 from most good ladder equipment suppliers Ladder Mitts are a great buy and I recommend them highly.

Monday, 29 November 2010

Ladder Test Rig - The Slipping Point

An overnight snowfall was enough to put me off work for the day and, for want of something better to do, I decided to find out more about ladder slippage.

There's lots of websites with all sorts of technical explanations about the forces acting on a ladder but all the ordinary working man (or woman) like me wants to know is the answer to simple questions like 'Will my ladder stick on this surface when its damp?' or 'How much higher can I climb safely before it slips?'

If only the answers were as straightforward as the questions!

Actually it is quite simple, to a point. As long as the horizontal force due to friction, between the feet of the ladder and the ground that it is stood on, is equal to or greater than the downward force exerted by the person climbing the ladder coupled with the leverage due to the ladder's angle; then all will be well. But how can you be sure? Ah... that's the tricky bit.

Having been thoroughly baffled by the boffin's answers on the web I decided to do some practical experiments - all I needed was a test rig.

My small ladder just happens to be 4.1 metres long so, with a metre rule to measure the horizontal distance from the wall, it was quite easy to attain the optimum leaning angle of 75 degrees. A pile of bricks and paving slabs from the garden and a wire basket out of our old freezer weighed in at about 83kg (13 stones) so representative of a typical adult male. With some rope and pulley blocks borrowed from my friends boat I hoisted the weight on the fourth rung from the top of the ladder (3 metres of it's length from the ground) to simulate typical working conditions and we were good to go. The ladder itself weighs in at 9kg giving a total weight of 92kg; The load acting downwards at a point roughly 25cm from the wall

With a second ladder and a set of spring balance scales I was ready to measure the forces acting on my ladder.

Testing the force needed to make a ladder slip

  1. The top of the ladder was exerting a pressure of 15kg against the wall.
  2. Force acting vertically downwards on ladder feet. When I tried to measure this,, using another set of pulley blocks to hoist the bottom rung of the ladder vertically, the spring balance went off the end of the scale at 100kg without the ladder lifting at all. Maybe this was due to either: (a) friction between the top of the ladder and the brick wall -15kg of leaning force multiplied by friction co-efficient of rubber on brick- or perhaps (b) torque- the ladder is actually pivoting about the point of contact with the wall and therefore the weight is multiplied by the leverage created by the horizontal distance between where the weight is hung and the foot of the ladder (75cm) or (c) a combination of both.
  3. Although I didn't understand all the physics, one website I looked at seemed to suggest that the horizontal friction force preventing the ladder slipping was the same as the force pressing the top of the ladder against the wall = 15kg. But I doubt this as I could not move the foot of the ladder inwards at all. However without putting wheels on the bottom of my ladder I couldn't find a way to measure it.
  4. Additional force needed to cause horizontal displacement. On my driveway, rough concrete, I tried to pull the foot of the ladder away from the wall horizontally to test the amount of friction between ladder and ground. This actually proved to be very difficult to measure accurately as it was almost impossible to get both stiles to slip simultaneously but slippage generally seemed to occur at about 90-92kg = roughly the same figure as the combined weight of ladder plus load. This would seem to suggest that a 26 stone man (without any additional weight of tools etcetera) could climb the ladder to the same height without it slipping (but see 5 below) so at just under 11 stone I should be quiet safe on wet, but rough, concrete (warning note - the safe maximum working load for most portable aluminium ladders quoted by manufacturers is 150kg = 23 stone). HOWEVER, in my tests most often one foot of the ladder slipped before the other - sometimes at loads as low as 80kg - so it is absolutely imperative to make sure the ladder is placed with the load evenly spread between both feet and also not to push your luck.
  5. In reference to point 4 above - if you double the height of the ladder to 8 metres and distance from the wall to 2 metres the ladder will not allow 23 stone on the 4th rung from the top due to (a) The distance of the ladder feet from the wall has increased but the distance of the load from the wall is the same - therefore the load exerts more leverage (b) the size of the ladder feet is unchanged so the friction does not increase either.
  6. I also tried varying the angle of the ladder against the wall. At an angle of 68 degrees (foot 1.5metres from wall) the ladder only required a horizontal load of 74 kg before it slipped. Clearly not so secure but should be okay for a climber of up to about 24 stone. My driveway wasn't wide enough to try shallower angles but I know, from other stuff I've read, that below 60 degrees the grip of a ladder on the ground falls off dramatically. The condition of the ladder feet is also critical to how well it will grip.
Of course we already knew this because every day thousands of us climb a ladder stood on concrete or tarmac at 75 degrees and it never slips - the difference is that now we know why and what the limits are. But what about other surfaces like wooden decking, smooth concrete paving slabs (especially when wet or slimy) or gravel?

Those are questions that I will attempt to answer another day but for now I'm happy with my test rig and with placing my ladder on rough concrete knowing that it is unlikely to slip, even in the wet, unless I do something really stupid!

Safe climbing!

Tuesday, 16 November 2010

A Touch of Frost - Try the Boot Test

Cold weather is a time when extra caution is called for when climbing a ladder. That patch of green algae on a paving slab may be innocuous enough when it is dry in the heat of summer but come the autumn and a bit of rain, or a touch of frost, and you might as well be putting your ladder up on black ice.

The vast majority of ladder accidents occur because the foot of the ladder slides away from the wall that it is leant against, usually due to a lack of grip. Worn ladder feet or damp and frosty conditions make the situation much more dangerous.

If in doubt try 'The Boot Test'

Quite simply scuff the sole of your boot on the ground in the exact spot you intend to place your ladder and see how well it grips or if it slips. The sole of my boot (size 8) is about 20 square inches (125 square cm) of rubber. If that won't grip firmly on the surface you can be absolutely certain the mere couple of square inches of a pair of ladder feet won't either, especially at an angle with my weight at the top of it.

The solution is simple - secure the ladder to an immovable object or use an anti-slip device.

So don't take risks with ladder safety - put the boot in!