2021 in review
It’s been a while since we posted an update. A decent amount has changed over 2021 so here’s a recap.
May 2021 — Ground investigation
To determine the most appropriate foundation design the ground beneath the site was examined. This involved desktop studies, trial pits, soil samples, rotary cored bore holes and lab analysis of the various rock and soil strata.
The investigation concluded that:
- The site is stable and with good building design will become more stable.
- The is cliff regressing towards the plot but very slowly with a regression of about 1m every 100 years. The terrace is around 17m from the edge so we’ve got about 1700 years before there is an issue.
- The ground is made up of 10–15m of firm clay on top a layered sandstone (visible on the cliff).
- The sandstone layer is level over the site
- Both the clay and sandstone are strong enough to bear the building
- Evidence of movement of top soil was found but top soil will be removed or stabilised by the build
Aug 2021 — Structural foundation design
The aim of the ground investigation was to provide our architects and engineers the data needed to design an appropriate building for the site.
The foundation options we were looking at were:
- Strip foundations — traditional concrete channels on which walls are built
- Piled foundations — concrete or steel poles inserted vertically into the ground and support the weight of the whole building
- Raft foundations — a solid concrete slab distributes the load over a bed of insulation.
We ended up choosing a raft foundation as it means the house is then entirely wrapped in insulation. This is one of the easier ways to achieve Passivhaus levels of insulation as it avoids ‘thermal bridges’ — things which conduct heat from the warm interior to the cold exterior.
The building design has also been tweaked such that the lower ground floor will create a retaining wall from east to west.
November 2021 — Structural building design
Once the foundations were designed the detailed structural design of the house could take place. There are two parts to the structure, the main floor and the smaller lower ground floor.
The lower ground floor will be built using ICF (Insulated Concrete Formwork). This will provide strong walls to retain the ground as well as a highly insulated and airtight shell. The roof will make up the upper terrace and comprises of a steel frame and a beam and block infill.
The main floor will also be built using ICF however as the southerly and westerly elevations are largely glazing a steel frame was chosen. Large steel beams enables a cantilever over the glass to glass corner windows. The roof will be a warm flat roof comprising of a primary steel frame and open web joists to support the green roof.
Next steps
We are currently tendering for contractors. The most critical part is the groundwork which would benefit from taking place in the drier months of the year. We’ve had great interest in the project so far and look forward to getting a start date agreed.
