Project Details:

Concreted Area:


Covered Storage Area:


Production Area:


Office Sales Welfare Area:



Thornbridge Sawmills Ltd.

Main Contractor:

BHC Ltd.




WMR Consultancy


Bruce Muirhead
MD, Thornbridge Sawmills
Ian Low
Agent, Thornbridge Sawmills

thornbridge sawmills grangemouth structural steelwork project

Redevelopment of Sawmill and Operations for Thornbridge Sawmills Ltd.

When Thornbridge Sawmills Ltd. decided to re-build their existing operations on their established site at Laurieston Road, Grangemouth, BHC Ltd. were given the opportunity to cost the proposed complete Design and Build project.  BHC Ltd. were given the brief of the proposed requirement and worked with Thornbridge Sawmills Ltd. to achieve the best possible layouts, storage capacities, and cost effective build.

BHC Ltd. were appointed as the main contractor and carried out all the works from design and obtaining the local authority approvals, through to fitting the carpets and handing the keys to the client.  All of the work (except the M & E, joinery in the first building, internal decorating and laying the floor coverings) was carried out by BHC Ltd. employees.

The site covered 26,402 square metres (6.521 acres) in total; of this 7,364 sq metres of buildings were erected.  BHC fabricated and erected 535 metres of heavy security fencing around the site along with 157 metres of chain link fencing.

Complete new foul and surface water drainage, including 160 cubic metres of attenuation before outflow to the public sewer, were included in the project.  The surface water drainage required 465 metres of open linear drainage ducts covered with galvanised steel grids.

A new 1000 KVA electrical substation was obtained and a switchroom built to feed all four separate buildings with power via underground ducting. Ducting was also installed around the site for ten external floodlighting columns; the floodlighting was supplemented with lamps fixed to the exterior of the buildings.

A new water supply was also obtained to serve five fire hydrants as well as the welfare facilities in three separate buildings.

The whole site was then capped with a fibre-reinforced concrete slab; total area including the concrete floors to the buildings was 26,092 sq metres (6.445 acres).

All this work was carried out as Thornbridge Sawmills Ltd. continued their day-to-day operations. And with careful planning between them and BHC Ltd., they never lost a day's production throughout the duration of the project.

thornbridge wood centre structural steelwork project

Building No. 1

This building had a ‘stand-alone’ function as a trade centre, to sell timber products, tools, ironmongery, etc. to the joinery and building trades.
The building incorporated 1,122 sq m of warehouse floor area including 163 sq m of gallery floor, 177 sq m of showroom, sales and office area and 38 sq m of welfare facilities.

The building has a steel portal frame construction with steel beams over the showroom/sales area to provide an area above to store materials.  The gallery floor consisted of fire-protected steel beams over timber storage racks with a concrete floor on Holorib decking, complete with steel stairway, external emergency escape stair, edge-protection rails and forklift loading docks. The building was clad all round with insulated composite panels to a 450mm high facing brick cavity wall. The roof was clad with insulated composite panels incorporating factory-assembled roof lights.

Two 5000mm X 5000mm insulated slide-over doors provided the access to the warehouse and double aluminium fully-glazed doors provided access to the showroom. Another set of double aluminium half-glazed doors were fitted between the showroom and the warehouse. Four metal fire escape doors were also fitted.

Five aluminium double-glazed windows were fitted in the cladding to the sales area, office and welfare facilities.  These windows, and the front entrance door, are protected by electrically operated aluminium security shutters, concealed within the wall cladding.

Internally, a perimeter dense concrete block wall 2450mm high was built inside the cladding rails.  The internal divisions were built off the floor with dense concrete blocks, some strapped and lined with plasterboard, while the toilets were fully tiled.

Full M & E installation was carried out by our subcontractor, including fire alarm circuits and a security system. The showroom, offices and welfare facilities were fitted-out and painted. Joinery and decorating subcontractors were employed by BHC Ltd. for these tasks.

thornbridge redwood plywood building structural steelwork project

Building No. 2

This building was for the storage of redwood and plywood and for timber treatment. A further extension accommodates Thornbridge Joinery Division.

The Building consisted of a steel portal frame with a clear span of 44.250 metres, covering 4,339 square metres; it was divided into four compartments, with full height dense concrete block fire walls.

Redwood Section:
One gable at the 1,080 sq m redwood storage is open and has a canopy cantilevered over a loading area.

Plywood Section:
Access to the 1,080 sq m plywood storage compartment is via two electrically operated, insulated slide-over doors.

Timber Treatment Section:
The treatment plant compartment covers 975 sq m and has a 7,000mm wide x 5,000mm high access door fitted with an electrically operated slide-over door.  The floor to the treatment plant incorporates a kerb around the perimeter, sealed to the floor to form a bunded area complete with two pumping sumps. The client fitted a new treatment plant and cantilevered racking for storage of finished products. The ridge to the above three compartments was fitted with a continuous natural venting ridge upstand.

Joinery Section:
The compartment constructed for the Joinery Division covers 1,204 sq m; the west elevation is skewed to run parallel with the site boundary.  Access is via. one 5000 X 5000mm doorway, fitted with an electrically operated insulated slide-over door.  The client fitted NC tooling etc. to this area along with oil-fired blown air heating.

The whole building also incorporated ten emergency exit doors.
M & E was installed by our subcontractor and incorporates a fire alarm system, lighting circuits switched via a time clock, as well as photocells.

thornbridge sawmill structural steelwork project

Building No. 3:

Of the three, this was the most challenging to construct, as it was to be located in the same position as the existing working machine milling area, which operated fifteen hours daily from Monday to Friday.

thornbridge sawmill construction project

BHC Ltd. designed the building to be wider than the existing one, and therefore erected the steelwork and roof over the existing building without disturbing the fabric.  When the new building was watertight and secure, the existing structure was demolished by hand, inside the new building over a number of weekends.

To accommodate the laying of the new concrete floor, some machine tools were removed to another building temporarily.  The new mill floor area totals 1,161 sq metres. Five slide-over insulated doors were fitted with 100% duty gear and electrically operated by remote controls to accommodate the forklift movements to and from the building.

The building incorporated a two storey office block at one end giving 466 sq metres of floor area. The ground floor accommodates the gents toilets, shower room, kitchen, first aid room, disabled and ladies toilets, mill and yard manager’s offices and a general transport office. The first floor accommodation includes the accounts office suite, canteen for all employees and additional gents and ladies toilets. All complete with internal stairway and second external escape stairway.

A 557 sq m extension was then added to the other end of the mill building to provide storage for the finished joinery products. Again the M & E work was subcontracted along with the decoration and the laying of the floor coverings.  All other work was carried out by direct employees of BHC Ltd.

The building has a full fire alarm and security systems.

The Mill Building was constructed of a steel portal frame 27m span with insulated composite wall panels to a 450mm high facing brick cavity wall. The facing brick wall was built to above ground floor window height around the office block.  Internally a dense concrete block wall was built to 2450mm above floor level. A dense block fire wall was built between the mill area and the office block. Insulated composite panels complete with rooflights cover the roof. Aluminium framed double glazed windows were fitted to the office block all powder-coated to match the cladding.

The first floor is a concrete floor laid on Multideck 60-V2 steel decking on fire-protected steel beam supports.

A 63 sq m tool room was built within the mill area with dense block walls, double-glazed fixed windows and a concrete roof on metal decking to keep the noise of the working mill machines to a minimum inside the tool room.

Sawdust extraction ducts, ventilation for the tool room and external oil-fired hot air heater ducts had all to be incorporated in the walls of the mill area.

All of the buildings feature a roof safety line system with access ladders to each roof.