Prefabrication: the work that happens at your own pace

The key to speed on site is doing everything slow before you arrive. Panel fabrication, cladding, painting, window fitting, all happen in a barn, a workshop, a car park, or on the building site itself, over weeks or months, with no weather dependency and no critical path pressure.

Ground screw foundation

Before any panels arrive, the foundation must be installed. This is a half-day task for two people. No concrete. No rebar. No curing. No weather dependency.

  • Mark out building perimeter with string lines
  • Install 12-16 helical ground screws using handheld hydraulic driver
  • 10-15 minutes per screw, any weather, any soil type (except bedrock)
  • Check each screw for plumb and level as you go
  • Bolt sill beam to screw heads, the foundation is complete

Time: 3-4 hours. Crew: 2 people. Tools: handheld driver, level, tape.

12-16
screws for 37.5m²
10-15 min
per screw
€1,800-2,500
total installed

Panel fabrication on a jig

Each RCP panel is fabricated flat on a simple jig, two sawhorses and a plywood sheet. The process is identical for every panel, so speed increases with repetition.

  • Lay EPAL pallet on jig, check for twist (replace if warped)
  • Apply continuous bead of PU adhesive to all contact surfaces
  • Lay first OSB skin, align to pallet edges
  • Fix with ring-shank nails at 150mm centres through OSB into pallet stringers and blocks
  • Flip, repeat for second skin
  • Stack flat, weight with other panels to ensure even pressure while adhesive cures

Rate: 5-6 panels per hour for a team of 4 (one cutting, one gluing, two nailing). For 44 panels: approximately 8-9 hours of fabrication work.

5-6
panels per hour
44
panels for 84m²
1 day
panel set complete

Why this is not factory production. A factory needs capital, machinery, a building, staff, logistics, and overhead. A Hestia panel jig needs two sawhorses and a nail gun. The work can happen in a village hall, a borrowed barn, a rented workshop, or on the building site itself. The system scales with the number of people who know the protocol, not with the size of the facility. We take our inspiration from WikiHouse, who proved that digitally fabricated, open-source building systems can generate real community momentum through technical transparency.

Under two weeks: the complete sequence

STEP 1 Day 1 Ground screws + sill beam STEP 2 Days 2-5 Wall panels bolt to sill, to each other STEP 3 Days 6-10 I-joists + roofing drop into hangers, seal STEP 4 Days 10-14 Weathertight windows, seal, inspect

This is the critical path. Everything before this was preparation. Everything after this is finishing. The assembly itself is pure connection: panels bolted to the foundation, bolted to each other, roof dropped into place, sealed. No concrete. No rebar. No curing. OSB, pallets, I-joists, and ground screws.

Days 1-2

Wall panels: raise and connect

Sill beam is already bolted to ground screws. Panels are stacked nearby, cured, pre-finished.

  • Two people lift one panel (44 kg) and slot it onto the sill beam
  • Panel is held vertical by a temporary brace or a third person
  • Next panel is lifted and butted against the first
  • Bolt through pre-drilled holes in corner blocks, M12 bolts with washers
  • Continue around perimeter: 4 people, one panel every 10-15 minutes
  • Check squareness with plumb laser as you go
  • Install corner bracing (temporary timber diagonals)

Result: All wall panels standing, bolted, square. Approximately 2 days for a 37.5m² module.

Days 3-5

Top plate, ceiling, roof structure

With walls standing, the horizontal structure goes in. This is the most satisfying phase, the building becomes rigid.

  • Install double top plate: two courses of timber bolted through wall panels, tying the whole perimeter together
  • Drop I-joists into standard joist hangers at 400mm centres
  • I-joists rest on top plate, no notching required (follow manufacturer tables for bearing length)
  • Lay ceiling pallets (OSB-faced, same construction as walls) between I-joists
  • Install purlins on top of I-joists at 600mm centres
  • Lay steel roofing sheets (or membrane + battens, depending on specification)
  • Seal every screw penetration with butyl tape

Result: Structure is complete and weathertight. Approximately 3 days.

Days 6-14

Seal, secure, inspect

The shell is up. Now it must be sealed against wind and rain, and checked for squareness and level.

  • Walk every seam. Check OSB-to-OSB joints for gaps. Seal with flexible tape where required
  • Install breather membrane over all exterior OSB (if not pre-applied)
  • Install window frames into pre-cut openings (frames were fitted during panel fabrication)
  • Seal window perimeters with expanding foam and flexible tape
  • Install door frame and door
  • Check all bolted connections are tight
  • Remove temporary bracing
  • Photograph every panel joint, every bolt, every seal, this is your as-built record

Result: Weathertight shell. Ready for services and interior. Total assembly time: under two weeks from first panel lift.

Finishing: the work that happens at your own pace

Once the shell is weathertight, the pressure is off. Services and interior can proceed in any weather, in any order, at any pace. Some tasks require licensed professionals for sign-off. Most do not.

Services (licensed professionals, short engagements)

  • Electrical first-fix: Cables run through pallet voids. No chasing, no drilling. 4-6 hours for a competent electrician to lay and terminate all circuits.
  • Plumbing rough-in: PEX water pipes through voids. Waste lines through floor voids. 4-6 hours.
  • Blown rock wool insulation: Professional contractor with blower machine. Fills all wall and roof cavities in 2-2.5 hours. 634 kg for 84m² home.
  • Solar PV installation: Panels on roof, cable to inverter, inverter to battery. Off-grid capable in one day.

Interior (self-build or any tradesperson)

  • Gypsum board lining: Screw directly to interior OSB face. No studs to find, the whole surface is structural. 2-3 days.
  • Floor finish: OSB floor deck + underlay + laminate, vinyl, or timber. 1-2 days.
  • Kitchen installation: Standard flat-pack units. Wall cabinets screw directly to OSB.
  • Bathroom pod: Pre-fabricated wet room pod or traditional tiling on cement board.
  • Limewash or paint: Interior and exterior. Breathable finishes maintain the vapour-open assembly.

Off-grid systems

  • Solar PV (1.5-3kW): Panels on roof, inverter, battery storage (5-10kWh)
  • Solar hot water: Evacuated tube collector, 200L tank
  • Rainwater collection: Gutters to storage tank to filtration to tap
  • Composting toilets: No sewer connection required
  • Smart home sensors: Shelly modules in voids, WiFi-connected, open-source firmware

Complete timeline from decision to move-in

Decision and planning2-4 weeks
Permits and approvals4-12 weeks (varies by jurisdiction)
Material procurement1-2 weeks (all off-the-shelf)
Panel prefabrication1-2 weeks (at your own pace)
Foundation (ground screws)1 day
Assembly (weathertight)Under two weeks
Services and insulation1-2 weeks
Interior finishing2-4 weeks
Total (typical)3-6 months

Compare to conventional construction: 12-18 months from planning to occupation. The Hestia system removes the foundation curing period, the weather-dependent external works, and the specialist-trades bottleneck that makes conventional construction slow. A single parent on a median salary, with €15,000 saved and a €30,000 loan, can afford a three-bedroom home. It is our job to make that enough.

One truck. One trip. Everything.

The entire material set for one 37.5m² module fits on a single flatbed truck. No wide loads. No escort vehicles. No crane required. Flatpack delivery to any site accessible by a standard lorry.

Material delivery for 37.5m² module

90 EPAL pallets~2.2 m³, stackable
32 OSB3 sheets (2500x1250x15)~1.5 m³, flat stack
24 I-joists (5m)Long bundle, roof rack
16 ground screws~100 kg, crate
Insulation, fixings, membranes~500 kg, bags
Total weight~4,500 kg
Delivery distance (typical EU)50 km average
Transport CO₂~0.8 tonnes

Compare: concrete-based construction for equivalent size = ~8 tonnes CO₂ (cement production + steel + transport). Hestia reduces transport emissions by 90% and eliminates the 5-8 tonnes of embodied carbon from concrete and steel. The house is over-engineered, but the footprint is minimal.