Setting Up a Welding Shop by the Numbers
Chapter 2 of 10 · 10 min read
The floor and the layout
Size a small welding shop's floor from its largest jobs and its zones, lay out the flow from steel rack to dispatch, and keep welding, grinding, visitors and flammable materials where they belong.
A rented unit is a rectangle of concrete with a roller door. Turning it into a working shop means deciding where everything goes: the steel rack, the saw and its infeed, the fabrication bays, the welding bay, the grinding area, the bench and machines, the gas cylinders, the office and the way out. The layout decides how far steel is carried, how often people walk round each other, whether a finished trailer can leave without moving three other jobs, and whether sparks and fume end up where they cause trouble. It is far cheaper to get it right on paper than to move a steel rack after it has been bolted down.
This chapter sizes the floor from the shop’s largest jobs and its zones, lays out the flow of work, and applies the early writers’ advice about where to put the welding outfit to a modern shop.
Start from the largest job
The floor must hold the largest job the shop will regularly do, with room to work all round it. For Mara’s shop, the largest regular job is a farm trailer up to about 6 m long and 2.4 m wide, built on stands. A welder needs about 1.5 m of clear floor on every side to work, set down tools, move a welding lead and get out of the way of a swinging part.
- Job length × width
- 6.0 m × 2.4 m
- Working clearance each side
- 1.5 m
- (6.0 + 3.0) × (2.4 + 3.0) = 9.0 × 5.4
- area ≈ 48.6 m² for one trailer bay
A trailer bay of about 50 m² is roughly a quarter of a typical small industrial unit, which shows how much one large job decides. A shop that wanted to build two trailers at once would need about 100 m² for them alone.
The zones
Beyond the largest job, a jobbing shop needs a set of zones, each sized for what happens in it.
The zones add up to about 200 m², and aisles, dispatch and the space needed to move a forklift add about a quarter, giving about 250 m². Mara’s chosen unit is 20 m by 12 m, 240 m², a little tight but workable if the layout is efficient and the cylinder store is outside. A larger unit would have cost more rent every month for space the first year’s work did not need, and Chapter 8 shows how directly rent flows into the hourly rate.
The cutting line
The cutting line is often the zone that surprises new owners. A saw cutting stock lengths needs room for the full length on the infeed side and for the longest cut piece on the outfeed side, in a straight line. This is an illustration. If the shop buys steel in 8 m lengths and cuts pieces up to 8 m, the saw needs about 8 m of infeed, the saw itself, and 8 m of outfeed, about 17 m in a line, nearly the full length of a 20 m unit. The line usually runs along one wall, with the steel rack beside the infeed so that lengths are lifted from the rack straight onto the rollers. A plasma cutting table, if the shop has one, needs room to load full sheets, which is another reason to plan the cutting zone before anything else.
The flow of work
Work in a fabrication shop moves in a sequence: steel arrives and is stored, is cut and prepared, is fitted and tacked, is welded, is ground and finished, and leaves. A good layout puts the zones in that order along a path, so that each job moves forward without crossing other work or going back on itself.
- Receive and storesteel delivered through the roller door to the rack
- Cut and preparesaw line along the long wall; plasma and drill nearby
- Fit and weldtrailer bay at the far end; screened welding bay beside it
- Grind and finishgrinding area between the welding bay and the door
- Dispatchfinished jobs leave through the roller door; nothing crosses the cutting line
Mara’s plan puts the roller door at one end of a long wall, the steel rack and cutting line along that wall, the trailer bay at the far end, the welding bay and bench along the opposite wall, and the grinding area near the door, so that finished work moves towards the door as it is completed. Repairs, which arrive and leave quickly, use a bay just inside the door, so that a customer dropping off a broken part does not walk through the fabrication work.
Where the welding goes
Dunham’s advice in 1917 on locating the welding outfit in a garage still applies. Keep it away from any part of the shop where petrol vapour may be present, because any flame is hazardous there. Keep it where visitors are not allowed, because people unfamiliar with welding trip over hoses and cause burns. Isolate it, because good welding needs concentration and the noise and glare make conversation with the welder impossible. And, Dunham added with a trader’s eye, keep it out of the customer’s sight, because a customer who watches fifteen minutes of welding may balk at paying a couple of dollars for it, not knowing that gas, filler and flux are part of the cost as well as the labour.
In a modern shop, the welding bay is screened so that arc light does not reach other people, placed where the fume extraction can serve it, kept clear of combustible storage and away from the paint and solvent store, and sited away from the office and customer area. Chapter 7 deals with the fire precautions.
The welding table
Both Willis and Dunham described the welding table. Willis suggested finding an old machined casting, ideally a planer bed, from a scrap dealer, thick enough not to warp in the heat, or else building a table of angle iron or bar covered with fire brick; he listed about 200 fire bricks among a repair shop’s needs. Dunham described an angle-iron table with welded joints, a shelf for rods and fluxes and a top of fire brick, large enough to hold a crank case and to build a temporary brick furnace on.
A modern shop’s welding table is usually a thick steel top, often with a grid of holes for clamps and fixtures, flat enough to set out work accurately and heavy enough to stay flat. It doubles as the work return connection for welding, so it must be connected properly, and its height suits the welder and the work. Mara planned one fixture table about 2.4 m by 1.2 m in the welding bay, and stands and trestles for the trailer bay.
Grinding and sparks
Grinding throws a stream of hot sparks several metres, and grinding dust settles everywhere. The grinding area should be placed where sparks fall on steel or concrete, not on cylinders, timber, cardboard, cables or other people, and where its noise and dust can be contained. Screens or curtains help, as does orienting the work so that the sparks fly towards a wall. In Mara’s plan, grinding is between the welding bay and the door, facing a blank wall, with the cylinder store outside on the other side of the building.
Lifting and moving
A jobbing shop moves heavy steel every day. Mara planned to share a forklift with the neighbouring unit under the lease, and to fit a lifting beam with a hoist over the trailer bay. The layout keeps a forklift path from the door to the rack and to the trailer bay clear, with a turning space, which is one reason the aisles take a quarter of the floor. Forklift and pedestrian routes are kept apart where possible. A layout that puts a bench across the forklift path will be rearranged in the first month, or worked around, unsafely, for years.
Services on the plan
The layout also sets where the services go. Each welding position needs a power outlet of the right rating (Chapter 3), gas supply if piped (Chapter 4), and extraction (Chapter 5). The saw, drill and lathe need their own outlets. Compressed air is needed for tools and plasma cutting. Lighting needs to be good everywhere and very good at the bench and the welding bay, where inspection happens. Drawing the services onto the layout, before the electrician quotes, lets the electrician quote the job once.
The office and the customer
Customers need somewhere to stand, sign and pay that is not in the middle of the work. A small office near the door, with a window onto the shop if possible, keeps customers out of the welding and grinding areas, keeps paperwork clean, and gives Mara somewhere to quote and invoice. It also houses the first aid kit, the safety data sheets and the job records, and, being at the front, it is where the shop presents itself to the customers who pay for everything else in it.
Height, doors and the roof
Floor area is only part of the building. The roller door must take the largest job out, on whatever carries it: a trailer on its own wheels needs a door wider than the trailer and higher than its sides, and a chassis on a forklift needs room for the mast as well. Mara’s unit has a door about 4.5 m wide and 4.5 m high, enough for her trailers. The clear height under the roof and its trusses limits how high a lifting beam can be mounted and how tall a job can be stood up; a beam needs its own structural check, by an engineer, before it is fitted to a rented building, and the landlord’s consent. The roof also matters for ventilation and heat: a low, uninsulated metal roof makes a summer workshop very hot and traps fume near the welder’s head.
The floor itself
A welding shop’s floor takes point loads from stands, trestles and the forklift, heat and spatter from welding, and steel dropped on it. Concrete is the usual answer. Sealing it reduces dust and makes cleaning easier, but sealers can be damaged by heat and spatter, so the welding and grinding areas are often left bare. Marked lines on the floor, for aisles, bays and the forklift path, cost little and keep the layout from drifting. The floor must also be checked for drains, pits and trenches, where heavier-than-air gases could collect, as Industrial Gases by the Numbers explains, and covered or managed if the shop uses those gases nearby.
Planning for change
A layout is right for the work it was planned for. When the work changes, the layout should change with it, and some flexibility helps: mobile benches and tool trolleys rather than fixed ones, power outlets in more places than the first layout needs, and a cutting line and steel rack that can be extended. Mara drew her layout on squared paper at 1 to 50, with paper cut-outs for each machine and bay, so that she and Sam could try alternatives before moving anything, and she kept the drawing for when the work grew.
A failure: the rack by the door
This is an illustration. In the first week, Sam set up the steel rack just inside the roller door because it was the easiest place to unload the first delivery. Within a fortnight, the saw’s infeed rollers, set up beside the rack, blocked half the door, and the first trailer had to be lifted over them on its way out.
Mara moved the rack and saw back along the long wall, as the plan had shown, over a weekend. The move cost two days of both their time and a hired forklift, about A$1,800 of lost work and hire. The lesson was that the layout drawn on paper was right, and that convenience on the first day had been allowed to override it.
Exercise: two trailers at once
Mara is offered a contract for twelve trailers over six months and wonders whether she could build two at once. Using the trailer bay calculation in this chapter, how much extra floor would a second bay need, and where would it come from in a 240 m² unit?
A second 6 m × 2.4 m trailer bay with 1.5 m clearance needs another 48.6 m². If the two trailers sit side by side and share the clearance between them, the pair needs about (6 + 3) × (2 × 2.4 + 1.5 + 3) = 9 × 9.3 ≈ 84 m², about 35 m² more than one bay.
In a 240 m² unit that is already planned at about 250 m², the extra 35 m² would have to come from the repair bay and some aisle space, which would squeeze the repair work and the forklift path. Mara could take the contract by building the trailers in sequence, one at a time, with sub-assemblies such as drawbars and tailgates made on the welding table while the previous trailer is finished, or by renting extra space for the six months.
