Definition. "Garden office" here means a structure suitable for full-time desk work in Irish weather: insulated, dry, electrically safe, with daylight and ventilation. Not a glorified shed with a desk and an extension lead.
Planning permission for a garden office
Same rules as a shed (25 m², 3 m / 4 m / 2.5 m heights. See planning permission). The change-of-use question:
- Working from home as an employee: fine. Your domestic property is still domestic.
- Running a business with no public-facing visits: fine. Same as above.
- Running a business with clients visiting: change of use, needs planning permission.
Sleeping in the structure also triggers a change of use regardless of size. Bathroom plumbing brings Building Regulations into play.
The four spec tiers
| Tier | Materials | Electrics | Heating | Total budget |
|---|---|---|---|---|
| Basic | Pressure-treated 8×6 timber, basic insulation | Single power circuit, 4 sockets, lighting | Plug-in panel heater | €3,500-€5,500 |
| Mid | 10×8 timber, full Kingspan insulation, internal lining | Sub-board, multiple circuits, 6 sockets | Infrared panel or oil-filled rad | €5,500-€8,500 |
| Premium | 10×10 timber or PVC-coated steel, double-glazed full window | RECI-certified sub-board, RCBO, network | Mini-split heat pump | €8,500-€14,000 |
| High-end | SIPs construction, finished interior, full plumbing-ready | Multi-circuit, fibre, smart-home wiring | Heat pump + UFH | €14,000+ |
Insulation: what actually works
Three layers do the heavy lifting:
- 100 mm Kingspan or Celotex between studs in walls and roof.
- 50 mm under-floor insulation, often overlooked. The floor is where most heat leaves a poorly insulated office.
- Continuous vapour-control layer (VCL) on the warm side of the insulation, taped at all joints.
Mineral wool is a budget alternative but performs noticeably worse in damp Irish conditions: moisture lowers its thermal performance. Spending €150 more on Kingspan/Celotex repays itself within two winters in lower heating bills.
The cold-bridge problem
Shed framing creates cold bridges where studs touch the cladding. Heat flows through the studs and bypasses the insulation. The mitigation: a continuous insulation layer (25-50 mm Kingspan) on the inside face of the studs before lining. Adds €200-€400 in materials and transforms winter performance, eliminating the cold "rib" lines that show up on a thermal camera in poorly insulated garden offices.
Electrics: DIY vs sparks
Anything connected to the main consumer unit must be RECI-certified work. The legal/insurance line is clear:
- You can: dig the trench, lay conduit, pull cable, fit sockets and lights to second-fix stage.
- You cannot (without RECI): connect at the main consumer unit, issue the test certificate, sign off the installation.
A typical garden-office electrical install: armoured cable from the house, sub-board with RCBO, ring main for sockets, lighting circuit, optional extras (heater on its own circuit, network point). Budget €600-€1,200 for a sparks to do this end-to-end with a certificate. Your home insurance and any future house sale require the certificate.
Heating options ranked
- Oil-filled radiator (€60): plug-and-play, but expensive to run for 8 hours/day. Fine for occasional use.
- Panel heater (€100-€200): similar economics. Cheap to install, expensive to run.
- Infrared panel heater 0.5kW (€150): surprisingly effective for one person at a desk. Heats objects (you), not air. Lower running cost than convection heaters.
- Mini-split heat pump (€1,200-€2,500 fitted): the proper answer for daily use. Cools in summer, heats in winter, runs at ~3:1 efficiency. Pays back in 3-5 winters versus electric resistance heating.
Internet
Cheapest: powerline adapters or a fibre extender from the house, €60-€200, works in most cases but degrades through dense walls.
Proper job: run a CAT6 cable in the same trench as the armoured electrics cable. Zero extra labour cost if done at the time of the trench, materials €25 for the cable + €15 for connectors. Gives you wired gigabit and lets you put a separate WiFi access point in the office.
Ventilation
Required, not optional. Two cheap mitigations:
- Trickle vent in each opening (window + door): €15 each, fitted at order time or DIY in 30 minutes.
- Passive flue or PIV unit: €40-€150 depending on type.
Skip ventilation and you get mould inside 12 months in a sealed insulated structure. The damp from one occupant's breathing for 8 hours/day adds up faster than people expect.
Realistic timelines
- DIY weekend turnaround (basic): not possible. Insulation alone is a weekend.
- DIY 6-8 week turnaround (mid-spec): doable, working evenings and weekends. Sparks visit slots in for 1-2 days during this window.
- Turnkey contractor build: 4-8 weeks lead time, 2-3 weeks on site. €1,500-€3,000 in labour on top of materials.
The thing nobody tells you
Your garden office becomes part of your house's heat-loss budget. A poorly insulated garden office that you heat 8 hours a day costs €40-€80/month in winter at 2026 electricity prices. A well-insulated one with a heat pump costs €15-€25/month for the same use. Across a 6-month winter, the difference is €150-€330, which is a meaningful chunk of the spec-upgrade cost paying itself back annually.
Insulate properly, install a heat pump, ventilate. The €1,500 you save by going basic-spec costs €300/year in heating, every year, forever.