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Around the world the eyes of those who create buildings are fixed firmly on modular construction.  With such amazing benefits such as incredibly fast building time, cheaper delivery costs and considerably less impact on the environment compared to traditional construction, modular construction simply can’t be overlooked.

Despite the giant benefits and lowered risk profile modular construction are still fairly new to the world of medium to high rise buildings.  There are a lot of you out there scratching your heads about this topic, I know.  Since it seems so alien and weird to make buildings in a factory, yet so obvious are the benefits!  We wanted to help you out so we put together an insightful and straight forward guide to the most successfully used steel modular structures.  We hope that by peeling back a layer of mystery, and revealing the structural design differences between steel module types, that you’ll feel a bit more friendly with them!

The UK boasts the largest market for modular buildings and it is emerging as world leader in the use of these building systems to deliver medium to high-rise buildings.  The UK also has, arguably, the most diverse range of modern construction systems, from timber frame to Light Steel Frame (LSF) and from Structural Insulated Panels (SIPs) to Cross Laminated Timber (CLT).  Despite the wide range of building systems available the bulk of modular buildings in the UK are mostly variations on steel modular systems.  Such systems have emerged as a leading technology to achieve the most impressive build heights, the best safety records, the highest reliability, and fastest speeds of delivery.


Cold Formed (CF) Corner Posts

 

This system uses CF or “light gauge steel” corner posts to limit the amount of Hot Rolled (Red Iron) steel in the build.  The CF corner posts can also be formed to suitable shapes, such as “J” profiles so that additional flexibility in terms of the design geometry can be levered in order to allow more possibilities for module to module connections, better panel to panel orientation, and more versatility for cladding systems.

In this type of CF module design the walls are sandwiched between the floor and ceiling panels.  The load is considered to be Uniformly Distributed along the walls and corner posts.  This is a very important aspect of this design but it means that it is difficult to remove walls from any one side of the structure.  This makes the system less versatile in terms of the room layouts that can be achieved.

[half]CF Posts[/half]

[half]
lsf corner post for module[/half]

 

Style Structural Members Maximum Build Height Ease of Assembly
CF Corner Posts All CF Galv. Sections G+3 ***


Hot Rolled (HR) Posts

 

This system integrates HR (Red Iron) structural steel sections into the design in order to increase the overall build height.  HR posts can easily be swapped out for the CF corner posts in the previous design concept if the geometry of the steel stud and track in the walls are designed correctly.

In this type of module the load transfer is through the HR posts.  These posts can also be included along the length and width of the module to increase load capacity.  Load transfer into the walls should be avoided.  Additionally the use of HR posts means that it’s easier to include beams over large openings in the module sides which in turn leads to the possibility of designing more flexible room layouts than the CF system above.

 

[half]HR Corner Posts[/half]

[half]hr corner module[/half]

Style Structural Members Maximum Build Height Ease of Assembly
HR Posts CF Galv. Sections HR Posts (Zinc Primed) G+12 **

 


Hot Rolled (HR) Frame

 

A natural progression from the inclusion of HR posts into the module structure is the use of HR steel as ring beams around the floor and ceiling of the module.  This allows for improved lateral load transfer and open span modules. This method of construction can be fully welded or bolted assembly.  Modules with fully welded HR frames tend to be more rigid which is a desirable factor in order to achieve high modular buildings.

These modules use a point loaded structure, meaning that gravitational (downward) load transfer into the walls is avoided.  Again, this leads to a more versatile and configurable module capable of producing highly configurable room layouts.

HR Frame

Style Structural Members Maximum Build Height Ease of Assembly
HR Frame CF Galv. Sections HR Posts (Zinc Primed) HR Beams (Zinc Primed) G+12 to G+35 ****

 


Cold Formed Full Height Walls

 

A different way to achieve medium-rise build heights using CF sections only is to design the module with full height walls and suspend the floors and ceilings inside the walls.  In this type of design modules with back to back studs in the walls can be used to “double-up” or “triple-up” the load carrying capacity of the wall.  This allows for modules at the base of the building to be triple studs, modules half way up the building to be double studs and near the top of the building the modules only need single studs.  In this way an economic use of steel sections can be designed into the modular building system.

Open module sides can be achieved using HR steel “goal post” structures around or inside the walls.

 

modular wall stud variations

Style Structural Members Maximum Build Height Ease of Assembly
HR Posts CF Galv. Sections G+12 ****

 

Balloon v Platform

 

The use of full height walls means that the floors and ceilings of each module are suspended between the walls.  This style of module is very similar to a traditional method of timber framing called “balloon framing” in which the outside walls were erected first and the intermediate floors were then built within the walls.  Though there are some restrictions in terms of the overall building structural design balloon framed modules have been used successfully within the UK for a large number of student accommodation buildings.

The more recent method of framing used in construction is called “platform framing”.  With this method the walls are built between the floors and ceilings.  While this method might pose some difficulty in terms of gravitational load transfer through the floors and ceilings into the walls it is easier to achieve a “shear plane” across the entire building floor.  This is desirable in high rise building construction.  Depending on the load transfer mechanisms of the modular system, it might not be necessary to use the walls to transfer gravitational load, but again, this is a consideration that needs to be carefully balanced with the method of manufacture and structural loading scheme of the modular building design.

full height walls or full width floors

Conclusion

 

There are a number of different ways to design the structure of a LSF modular system.  The different methods should be carefully considered in terms of the pros and cons in relation to the manufactured method and desired product performance.

Though this page has been dedicated to steel modular systems there are a wide range of building systems on the market.  Not all of the systems available to you will be modular, not all of them will be steel.  From pre-cast concrete to cross laminated timber panel systems and from volumetric bathroom pods through to structural modular systems, the range of systems on the market is growing on a daily basis.

If you’re about to take your first footsteps on the path of modular building design then the construction of the module is just one of the primary design issues that you must address.  For help and more information on this topic or anything related feel free to contact us and ask any questions you might have.  We are here to help you make the most economic and effective choice for all your future construction projects.

 

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