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Under One Roof

Canadian Roofing Reference Manual

2.2.5 Spudding Machine

On all reroofing jobs and any major repair job, a roofer may be required to loosen large amount of the embedded gravel on the existing roof so as to access the roof membrane and perform a “tie-in”.

To spud a major “tie-in” or remove the gravel from the entire perimeter of a building by hand takes a lot of time and effort, especially in warm weather. To save time and energy a spudding machine can be used.

Before starting the spudding operation, you should always read and understand the manufacturer’s operating instructions.

Some models of roof cutters can be used as spudding machines. In these units, the cutting blades are removed from their mounts and a series of special rotary blades are attached.


Safety glasses or a face shield should be worn at all times when operating the spudding machine. Eye protection will help avert the possibility of injury from stones and debris while spudding and will help to avoid eye irritation caused by dust in the air while spudding.

Proper fitting clothes should always be worn when operating the spudder. Loose fitting clothes can be dangerous as they could cause serious injury should they get caught in moving mechanical parts. Tight fitting clothes can restrict movement and slow down reaction time in dangerous situations.

Operators should wear long sleeve shirts buttoned at the cuffs, pants without cuffs and safety shoes.

A hard hat should be worn when work is being done above.

When hoisting the spudding machine to the roof, use the hoist ring on handle or the hoist ring provided. Do not attach the hoist cable to any other part of the machine as this could damage the spudder.


Before starting the machine check to make sure that scratcher guard and belt guard are in place and all bolts are tightened.

The removal of the embedded gravel is done by carbide tips installed in a drum that rotates counter clockwise.

The carbide tips strike the gravel rapidly, loosening it from the flood coat. Sweep all loose gravel off the roof before attempting to spud.

Pushing down on the handle will lower the spudder to the deck. The depth control should be set to remove only the gravel and leave the roof membrane intact. The depth control is simply an adjustment screw that can determine the depth of the carbide tips. Clockwise adjustment of the screw lowers the depth setting, counter clockwise adjustment raises it. When the pressure is released on the handles, the machine returns automatically to an idle position. A too deep setting may cause the entire machine to raise or walk forward without removing any gravel.

Spudding machines are manufactured to remove either a 100 mm (4 in) or 400 mm (16 in) width of gravel.