Part 5: Superstructure

20 July 2016 Brent Ackerman, Delta Project Management
Brent Ackerman was the Project Manager for the build of our Elsworth show home and he’s also a regular presenter of the Self-Build Academy courses and events.

Below, Brent explains more about what superstructure is and the various stages of building the Elsworth show home.

1. Level the Sole Plates

Levelling sole plates on self build site
The first pieces of timber to get fitted on every project are never the most glamorous, but they’re arguably the most important.

A sole plate is a single strip of solid timber that runs around the top of the foundations and is fitted to the top of the “kicker brick” course — the last element of the foundations. It’s essential that the sole plates are level and set out accurately in accordance with the setting-out drawings.

Mistakes incorporated at this stage of the build invariably cause much bigger problems further down the line, so the job has to be done correctly. If there are any errors with the foundation construction, then these should be addressed before work proceeds.

2. Install the Ground Floor Panels

Groundfloor Structural Insulated Panels being installed
Once the sole plates are set, the ground floor internal and external Kingspan TEK® Building System wall panels can be delivered and erected.
The panels are fabricated in elevation or part elevation form, depending on the access conditions on-site, so that the number of joints requiring attention is minimised. The ground floor panels are first nailed to the sole plate and then fixed to each other.
The erectors brace the panels to ensure that they are vertical. The panel junctions are sealed with insulating foam and sealant to help ensure that they are airtight.
Corner junctions on the ground floor need particular attention, as they must be set square. Internal wall panels — which can be load-bearing, non-load-bearing or contribute to the overall building stability — get added into the structure as the build progresses.

3. Fit the Post and Beam Membranes

post and beam membranes
This Passivhaus is a challenge as it has large open-plan spaces on the ground floor, as well as a central courtyard area and a spectacular feature window that measures approximately 8x3m.
The courtyard is framed with four posts and the large openings are constructed using portal frames to provide stability to the structure. These large post and beam members are fitted as the ground floor build progresses and care must be taken again to ensure that they are accurately located and aligned.
Large members are typically fixed using resin anchors and shimmed (wedged using shims) into position with steel strips. It’s essential that once the resin fixings have set — and before the ground floor is screeded — the shims are grouted using a structural non-shrinking grout.

Building a Passivhaus Show Home

A complete step by step guide, we take you through the story of building our Passivhaus show home. From the design process, constructing the superstructure, achieving airtightness right through to the finishing touches.

Download the guide here.

Building a Passivhaus Download

4. Construct the First Floor

MiTek Posi-Joist Floor installation
We chose to construct the first floor using open metal web joists with Norbord Cabershield floor decking. We use open metal web joists (MiTek Posi-Joists) on all our projects as they really do simplify the installation of the services, particularly the large ducts, which are required by mechanical ventilation with heat recovery (MVHR) systems. Metal web joists can also be manufactured to a variety of depths and widths so that a range of span and load conditions can be accommodated.

The Cabershield chipboard is a new product for us and one that we now know works very well — a departure from traditional plywood. It has a permanent coating that protects the product from moisture during construction.

In this build, the Posi-Joists are hung off of the external Kingspan TEK® Building System walls using metal hangers to help reduce thermal bridging. The Cabershield floor deck is then glued and screwed using a special gap-filling adhesive to the top of the Posi-Joists.

The adhesive helps prevent squeaks and creaks in service and contributes to the moisture-protection performance of the system during construction.

5. Raise the Roof

Potton show home SIPs in construction
The Kingspan TEK® Building System 172mm panels, which are used for the roof, are capable of spanning over 3m without requiring any additional support. Where spans are longer than 3m, the panels are either sat on a load-bearing wall, supported by a purlin running underneath, or they have rafters incorporated into them.

While this overall build is somewhat complex, the roof itself is relatively straightforward, so we were able to design and deliver some large-format panels to simplify the build and reduce the time spent working at height. Once the large panels are laid on to the supporting structure, they can be nailed together and fixed through onto their supports.

6. Seal the Structure

Potton's Passivhaus show home SIPs shell
Being a Passivhaus, the building has to be extremely airtight, so all of the panels are pre-fitted in the factory with a Wraptite system membrane. Once the superstructure is complete, the final job is to seal up all of the panel junctions with a narrow sealing strip to provide continuity of performance.

The next step is fitting the Vieo standing seam roof from Euroclad and installing the roof light, along with the Kloeber windows.

Read Part 6: How To Build An Airtight House
Potton Elsworth Passivhaus Show House

The Elsworth is open to the public

We have five self-build homes for you to browse, but the Elsworth is the UK's first permanent show home built to Passivhaus standard, created using our Kingspan TEK Building System.

Come and experience the Elsworth show house for yourself.
Editor’s note: This blog post was updated in June 2019 for accuracy.

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