Architect Information

Standard Sizes


Anything is possible with the right budget, timeline and attitude! At LAROS we are taking a fresh approach to prefabrication so feel free to push the boundaries of contemporary design. Following the guidance below will assist you to take full advantage of the cost benefits of factory fabrication. Generally speaking, fewer larger panels will result in a lower build cost per sq m compared to many smaller panels.

Thickness – 249mm Standard

All wall panels are standard at 249mm thick from the inside of the wall lining to the outside of the vertical batten. This consists of 27mm 3-ply timber sheet, 200mm wall framing/insulation and a vertical 22mm timber batten. If you are planning to use a cladding product that spans vertically then you will need to add a further 35mm for a horizontal batten. Some extreme climates, sites or floorplans may require thicker framing/insulation to meet the Passivhaus standard.

Height – 2.7m Standard

Single storey wall panels are standard at 2.7m high but can be up to 3.3m high with excess road transport costs. If your design calls for taller walls (such as skillion or gable-end designs) then we can always stack wall panels to achieve the desired outcome.

Length – 11.5m Maximum

All of our panels are limited to the length of a standard shipping container – 11.5m. If you have longer walls then we will simply segment them in the most cost-effective way for your design. If you are looking for cost savings, the length of panels is a great place to optimise. The more panels that are as close to 11.5m as possible will mean you get maximum use of the shipping container space and reduce the amount of time the crane needs to spend on site. Our concept design team take all these factors into account when pricing projects. 

More than one storey?

Depending on the layout of your design, we may recommend either platform construction (stacking single-storey walls) or balloon construction (single panels that run the entire height of the building) or a mixture of both. Double-storey and triple-storey panels are constructed vertically so can be up to 11.5m high and 2.7-3.3m wide and may represent opportunities for cost savings. Our concept design team can advise you on which strategy works best for you.

Internal Walls

Love the timber look? Or maybe you want a more turn-key solution for your clients? We can supply internal walls with the same Tilly 3-ply timber lining and a narrower 70 or 90mm stud frame. We usually supply these with just one face of timber so that services can be easily installed on-site. We can then supply your builder with loose sheets of Tilly 3-ply to install on-site when ready. Alternatively, we can provide the wall panels with both faces timber-lined. Sometimes we may need to include internal walls in our scope where load-bearing internal walls are necessary to support long spans of roof or floor above. Contact us for more information.


Floor panels are available in a range of depths depending on the selection of flooring finishes, spans and loadings. As for walls, fewer, larger panels generally result in lower overall costs and make for a speedier build.

Thickness – 300-500mm Standard

The standard floor configuration depends on whether it forms a part of the external envelope of the building. External floors use a 22mm particleboard floor, 200-400mm structural timber framing with thermal insulation and a weathertightness membrane. Internal floors use a 22mm particleboard floor and 300-400mm structural timber framing. We can add acoustic insulation if required. In wet areas we replace the particleboard with a water resistant Magnesium Oxide sheet and can design for set downs as required.

Spans – 8.0m Maximum

Depending on loadings, spans up to 8.0m are possible, though the most cost-efficient span is achieved at approximately 6.0m. If your project needs longer clear spans or cantilevers, please contact our in-house structural engineer to discuss your requirements – remember, anything is possible!

Width and Length – 2.7m x 11.5m

Floor panel dimensions are typically 2.7m wide and up to 11.5m long however we tend to find that most projects are best suited to single span panels. Wider panels up to 3.3m are possible with excess road transport costs. Considering this in your design can have an impact on overall cost and timelines.


Like floors, roof panels are available in a range of depths depending on the selection ceiling finishes, spans and loadings. In addition the shape, pitch and ceiling type will impact the size, cost and time associated with manufacturing and installing a prefab roof. We can work with pitched roofs (hip- or gable-end), skillion roofs, parapets and more.

Pitch/Slope – 10-35 Degrees Standard

A wide range of roof pitches are possible with the LAROS system. We offer 10-35 degree pitch as standard but we can go both higher and lower to meet the requirements of your project. Roofs above 35 degrees require bespoke structural engineering. Roofs between 5-10 degrees require additional water proofing details. We strongly recommend against roof pitches lower than 5 degrees as we are unable to warrant the water proofing performance straight out of the factory. While we can supply roofs at very low pitches, a third party system would be required to guarantee watertight performance.

Thickness – 300-500mm Standard

The roof configuration consists of 27mm 3-ply ceiling lining, 300-400mm structural timber frame with thermal insulation, 15mm sheathing (for low pitch roofs only), weathertightness membrane and a 22mm batten along the slope for ventilation only. Roofing battens may also be required with thickness depending on the roofing material selected.

Spans – 10.0m Maximum

Depending on loadings, spans up to 10.0m are possible, generally the most cost-efficient span is achieved at approximately 7.0m. If your project needs longer clear spans or cantilevers, please contact our in-house structural engineer to discuss your requirements.

Width and Length – 2.7m x 11.5m

Roof panel dimensions are typically 2.7m wide and up to 11.5m long. Optimising a building’s design for maximum roof panel length is another good way to maximise the cost-effectiveness of prefab. however we tend to find that most projects are best suited to single span panels. 

Information Requirements

Prefabrication necessarily requires a more complete and detailed set of architectural drawings prior to commencement of manufacturing in order to achieve the cost and time benefits for the client. LAROS has a two-stage costing process. The first stage, indicative costing, is free and provides a cost range per sq m of floor area. The second stage, concept design, involves a detailed assessment of the project from which a contract can be drafted. For this reason it is essential that a complete ‘for-construction’ set of architectural drawings is provided to LAROS prior to contract execution.

Minimum information requirements for indicative costing

– Site location
– Desired thermal performance standard
– Floor to ceiling height
– Number of storeys
– Approximate floorplan
– Roof shape
– Approximate sizes and locations of windows and doors
– Elevated floor or slab-on-ground
– Any other special requirements (e.g. acoustic performance, special finishes, green roofs etc.)

Minimum information requirements for concept design, detailed costing and contracting

– Detailed, ‘for-construction’ architectural drawings
– Detailed window schedule
– Interior surface finishes
– Exterior cladding/facade requirements
– Occupancy information
– Scope inclusions – (External Walls, Internal Walls, Roofs, Floors)

Detailed Design

Once the contract has been executed, LAROS begins work on the detailed design phase. This is where the passive house prefabrication process differs from a regular build – we will need to know the fine details of surface finwhere services need to penetrate the envelope. We work with interior designers and clients to ensure these details are captured early on, such as:

– Water
– Hot water
– Wastewater
– Lights
– Switches
– GPOs
– Data points
– HVAC/ERV – including ducting, vents, power, refrigerant and condensate lines