# Homemade Scaffolding Tower – Part 2

In part one of this series on making your own homemade scaffolding tower I discussed the research and design aspects of building the tower. In part two I perform a few quick calculations to prove the platform will be strong enough and put together a parts list for the material purchase.

# Calculations

Having worked with wood for about 20 years I was sure that my design was strong enough but I thought it wouldn’t hurt to do some calculations to make sure. The biggest unknown for me was the platform as I’d never really made a span before so decided to calculate for that. I figured it was approximately the same as the floor of a house so I used the same calculations an architect or engineer would. First though a few definitions:

• Joist spacing is the centre to centre distance of the joists (typically 400 or 450 mm centres).
• Span is the clear span between supports.
• Imposed load is the person and any tools or materials.

Imposed loads should not exceed 1.5kN/m^2 for a regular floor (figures from BS6399-1, Current version is probably BS EN 1991-1-1:2002).

1 N = 1 kgm/s^2

Gravity (a) = 9.81 m/s^2

Since: F=ma

1500 = m * 9.81

m = 1500 / 9.81 = 152.9 kg

In other words 153kg evenly distributed over every square meter of floor.

The table below shows maximum spans (in meters) for C16 graded timber with the given centre spacing (columns)

 Timber 400mm 450mm 600mm 47 x 97 1.92 1.82 1.46 47 x 122 2.55 2.45 2.09 47 x 147 3.06 2.95 2.61 47 x 170 3.53 3.4 2.99 47 x 195 4.04 3.89 3.39 47 x 220 4.55 4.35 3.79

## Designed Platform

• Width: 840mm
• Length: 1800mm
• Joists: 47×100 C16 on 450mm centres
• Span: 1500mm

The designed platform has a surface area of 1.5m^2 which gives a maximum loading of 1.5*152.9 = 229.3kg evenly distributed and assuming exactly the conditions given in the table. My platform however has a span of just 1500mm, significantly less than the maximum allowable span for C16 timber of 1820mm. Additionally I’ve assumed a centre spacing of 450mm which is true for the two centre beams but not the beams to either side which are more like 300mm centres. I’ll also be screwing down a single sheet of 18mm ply over the platform which is much stronger than floorboards. All things considered I would be happy saying the maximum safe load is 300kg, more than enough for me and my tools.

# Material Purchase

From the design I put together a list of parts and I then mapped that onto timber that I could actually buy. I shopped around online for the best price and got the whole lot delivered for £225. The tables below show the parts list and the timber I bought.

## CLS Parts List

 Part Thickness Width Length Quantity Total Length Kickboard Long Support 50 50 100 4 400 Ladder Leg 50 50 1200 4 4800 Ladder Rung 50 50 250 8 2000 Long Rail Stiffener 50 50 1700 2 3400 Platform Stop 50 50 840 2 1680 Rail Support Block Small 50 50 100 4 400 Rail Upright 50 50 1200 4 4800 Cross Brace 47 100 2400 4 9600 Noggin (Short) 47 100 126 4 504 Noggin 47 100 400 3 1200 Platform Joist 47 100 1800 4 7200 Rail Support Full 47 100 846 2 1692 Rung 47 100 940 14 13160 Leg 47 150 2340 4 9360 Stretcher 47 150 1800 4 7200 Rail Long Stretcher 25 101 1800 2 3600 Rail Long Mid Stretcher 25 200 1800 2 3600

## CLS Timber

 Timber Size Total Length Bought Length Price Cost 50×50 17.5 20 £1.26 £25.20 47×100 33.4 40 £2.11 £84.48 47×150 16.6 20 £3.17 £63.36 25×100 3.6 4 £1.56 £6.24 25×200 3.6 4 £3.24 £12.96 Total £192.24

## Ply Parts List

All parts can be cut from a single sheet of 18mm ply costing £33.12.

 Part Thickness Width Length Quantity Platform Bed 18 840 1800 1 Cross Brace Gusset 18 225 240 2 Hatch Bed 18 440 440 1 Kickboard Long 18 150 1600 2 Kickboard Short 18 195 840 2 Rail Short Stretcher 18 100 840 2 Rail Support Plate 18 100 151 4

## Other Parts

 Part Notes Quantity M10 x100 Bolts Main frame, guard rail 32 M10 Washers Use thick repair washers 64 M10 Nylock Nuts 24 M10 Wing Nuts Guard rail 8 M6 x 70 Bolts Guard rail, platform locks 20 M6 Washers 32 M6 Wing Nuts 20 M5 x 50 Bolts Castor attachment 16 M5 Washers 16 M5 Nylock Nuts 16 4 x 50 Wood Screws Platform 30 4.5 x 70 Wood Screws Rails 64 6 x 150 Wood Screws 32 Exterior Wood Glue 1000 ml 1 Heavy Duty Castor 60kg or greater 4 Bottle Jack 1 Ton or greater 1

On to part three where I start the construction.