Architect, Karlien Thomashoff shares her first experience designing a light-steel frame house.
Walls & Roofs chatted to Karlien Thomashoff from Thomashoff + Partner Architects about designing the Stand 47 house on Monaghan Farm, for the first time making use of a light-steel frame construction system. Thomashoff is one of the most influential architects locally, with more than 20 years’ experience in the field.
As an example of a flexible housing typology that can adapt as the need for space changes over time, Stand 47 is the first light-steel construction house that was approved by the Centurion municipality since the new SANS energy regulations came into effect. The project was commissioned to showcase the potential of alternate building materials and green elements on a luxury home, without sacrificing quality, appeal or comfort.
Saint-Gobain’s light-steel cladding system, External Thermal Insulation Composite Systems (ETICS), was used in conjunction with natural materials and conventional building methods to demonstrate the intended innovation, efficiency and adaptability.
Marrying familiar interior finishes with the new, unknown technology subconsciously creates a reassuring effect and potential buyers probably would not even notice that a different building system was used, unless it is pointed out to them. Though contemporary and clean cut, the application of wooden window and door frames and natural stone walls add a bit of a traditional earthiness, together with terrazzo tiles that remind us of the 60s and 70s.
“Subconsciously, one relates to the things that are familiar to you and when the modern, unknown technology is introduced, it is not such a foreign concept to relate to,” explains Thomashoff.
The house was constructed on a raft foundation, which affords the freedom to modify with ease. It was split into a fixed services zone that includes the bathrooms, kitchen and scullery, and a flexible living zone, where the teak parquet floor and the suspended ceiling are continuous from the one side of the house to the other. The walls were added later on top of the floors and can be moved or modified as the need for the space changes, with minimal disruption and damage to the floors and ceiling.
For Thomashoff, one of the highlights of designing with light steel was the fine roof edge of only 90mm thick that she could achieve, something which is not possible with conventional construction methods.
All the beams are hidden inside the house and it is only the roof battens that extend outside the walls to create the overhang. Whereas normally, a thick facia is needed to hide all the roof components, a 100mm-thick square tubing was fitted around the whole roof, together with a customised flashing that Thomashoff designed to create the fine edge.
“It looks like a piece of paper that floats over the building. It is very sophisticated,” she comments.
An array of photovoltaic panels was also integrated into the design and blends in well with the roof, instead of looking as if it was added as an afterthought.
The walls of the rooms include Isover Cavitybatts and where they connect with the floors and ceiling, a sound seal strip was added, resulting in better sound insulation than provided by a conventional indoor wall. Gyproc’s Activ’Air performance plasterboards, which improve the indoor air quality, was also fitted. Gyproc FireStop walls were installed to improve fire resistance and Gyproc DuraLine in high traffic areas, was used for impact resistance
Although underfloor heating was originally planned, the thermal insulation of the ETICS system together with the double glazing of the windows proved sufficient to adhere to the SANS 10400XA regulations.
The bathroom walls include Gyproc’s MoistureResistant performance plasterboard with water-resistant properties. The walls’ strength capacity is demonstrated by the toilet that is hanging on the wall instead of being floor-mounted, for example. These walls can carry a load of 400kgon a single fitting, when consideration is given to the installation and bracing required.
Keeping it as natural as possible
Outside four water tanks can store 20 000l of rainwater and two conventional water reservoirs, heated by a heat pump geysers were fitted to provide the home with warm water at a lower energy demand than normal geysers. All external lighting is directed downwards to curb light pollution and keep the farm as dark and natural as possible. In addition, more than 50% of the 3 700m² stand will be rehabilitated and restored in order to maintain the natural farm landscape.
New material tried and tested
In another experimental installation, Rhino Modified Wood was selected for the window and door frames because of the material’s strength and weather resistance. However, according to Thomashoff, this type of wax-treated timber is very hard and heavy, which posed some design challenges, especially in finishing off the joints.
“It is a new type of wood that acts differently than what we are used to, and we realised a few challenges during the installation that we are busy addressing,” she says.
“Because it was the first time that we worked with this alternative construction method, we learnt a lot as architect team, as did everyone who worked on the project,” says Thomashoff.
“We had to find ways to resolve detail such as how to join the system to conventional walls, finish off openings and how to install doors between walls that are thinner than what we are used to. Things that have been second nature to us had to be reconfigured, especially because we care so much what the final product looks like.
“Also, in our drawings we had to work very accurately – up to millimetres, because the system is so accurate,” she adds.
She also explains that in order to make the most of the quick building potential, it is vital to have a good contractor and subcontractors who can deliver material on time and on spec, because when building faster, the material also has to be ordered earlier than normal to keep up with the building process.
“Working with new materials and a new system is always challenging, but the next time will be much easier since we now know how to plan for specific challenges in advance,” she concludes.
Read more about Stand 47 on page XYZ or visit the website: www.stand47.co.za.
Full thanks and acknowledgement are given to Thomashoff + Partner Architects for the information given to write this article.
Light-steel frame benefits:
Fine roof edge achievable.
Lighter walls that don’t need foundations.
More flexibility to modify interior.
Improved sound insulation.
Speed of installation
Less wastage of building materials