Quick answer
All three can meet the Future Homes Standard. Timber frame is usually the cheapest and goes up quickly. SIPs cost a little more but give the fastest, most airtight shell. Masonry is slower and weather-dependent, but it copes best with tight sites and late changes, and every lender and buyer understands it.
By Henry Lynch · Updated October 2026 · First published 15 August 2025 · Oxfordshire
How you build the walls and roof of a new home or an extension is a performance decision as much as a cost one. Since the Future Homes Standard was published in March 2026, it also affects how easily you’ll get through building control. Here’s how the three main methods compare, from a builder who works across Oxfordshire.
What the Future Homes Standard means for your choice
The government published the Future Homes Standard on 24 March 2026, as a new Approved Document L (now called Energy and Greenhouse Gas Emissions) and an updated Approved Document F. It applies in England and comes into force on 24 March 2027. If your building control application goes in before that date, you can still build to the 2021 rules, as long as work starts on site by 24 March 2028.
Four changes matter most when you’re choosing a structure:
- Solar panels. Most new homes need solar PV equal to about 40% of the ground floor area.
- Low-carbon heating. The reference home in the calculation has a heat pump, so a gas boiler won’t get a new home through.
- Tighter airtightness. The reference home’s air permeability drops from 5 to 4 m³/(h·m²) at 50 Pa, and it assumes mechanical extract ventilation.
- New calculations. SAP 10.3 is used for now, and the Home Energy Model will replace it.
In practice, the walls and roof have to perform as designed, and the air test at the end proves whether they do. A system that’s reliably airtight takes risk out of the build. A system that depends on careful site work needs a builder who takes airtightness seriously.
The three build methods
SIPs (structural insulated panels)
A SIP is a sandwich: two sheets of OSB3 board bonded to a rigid foam core, usually polyurethane or EPS. The panels are cut in a factory to your drawings, so the walls and roof go up in days and the shell is usually weathertight within a week or two. With so few joints, SIPs give the best airtightness of the three. The walls are also thinner than masonry for the same U-value, so you get more floor space on the same footprint.
The catch is that everything is fixed at the factory. Window positions, openings and service routes have to be settled before the panels are made, and late changes are slow and expensive. Use a system with a BBA certificate. Lenders and warranty providers look for one, and the certificates give a life of at least 60 years if the panels stay weathertight and dry.
Timber frame
Timber frame is a skeleton of studs and rails, made up into wall panels in a factory. Open panels are insulated on site. Closed panels arrive with the insulation, membranes and sometimes the windows already fitted. A frame for a typical house goes up in a few days and is weathertight in two to three weeks. It’s usually the cheapest of the three, and the lightest, which helps on poor ground and when you’re building upwards.
Airtightness depends on the membranes and tapes, so it’s only as good as the detailing and the care on site. Closed panels made in a factory are more reliable. The outside can be whatever you like: brick, render, stone or cladding.
Traditional masonry
Brick and block cavity walls are what most UK homes are built from, and every lender, insurer and buyer understands them. Masonry is slower. Eight to twelve weeks to weathertight is common, and rain and frost hold the work up. To reach modern U-values the cavity has to be wide and fully insulated, so masonry walls are the thickest of the three.
Masonry is forgiving, though. Openings can move during the build, and heavy walls hold heat and block sound well. Airtightness comes from a wet plaster finish or a parge coat, plus careful sealing around joists, windows and services. It’s achievable, but it needs attention.
Side-by-side comparison
The costs below are for the whole build, not just the structure, at a mid-range finish and 2026 prices. We combined several UK cost guides and widened the ranges. Oxfordshire and the rest of the South East usually sit in the upper half.
| SIPs | Timber frame | Masonry | |
|---|---|---|---|
| Whole-build cost per m² (mid-range, 2026) | £1,900–£2,900 | £1,750–£2,700 | £1,900–£3,000 |
| Time to weathertight | Within 1–2 weeks | 2–3 weeks | 8–12 weeks |
| Airtightness | Best, with few joints | Good with closed panels and taped membranes | Needs a wet plaster or parge coat and careful sealing |
| Wall thickness for the same U-value | Thinnest | Medium | Thickest |
| Changes during the build | Hard, as panels are made to order | Possible, at some cost | Easiest |
| Weight | Light | Light | Heavy |
| Lenders and warranties | Fine with a BBA-certified system | Widely accepted | Accepted everywhere |
| Expected life | At least 60 years (BBA), if kept dry | 60 years or more | 60 years or more |
The structure itself is only part of the bill. Industry guides put the frame at about 15–25% of the total build cost, so your choice of system usually moves the total by less than 10%. The finish, the size and shape of the house, and the site matter more.
Eight things to weigh up before you choose
1. Which rules you’re building to
Check your dates first. A project that goes to building control before 24 March 2027, and starts on site before 24 March 2028, can follow the 2021 rules. Anything later must meet the Future Homes Standard, so design to it from the start.
2. How far beyond the rules you want to go
If you’re aiming for Passivhaus, airtightness becomes the hardest target: 0.6 air changes an hour at 50 Pa. SIPs and closed-panel timber frame reach it most easily. Masonry can, but it takes more care on site. Our guide to EnerPHit explains the retrofit version of the standard.
3. Programme
A shell that’s weathertight in weeks rather than months lets the inside trades start sooner. Every week saved also cuts site running costs such as scaffolding, welfare and supervision. Our guide to preliminaries explains those costs.
4. Changes during the build
If you expect to change your mind about windows or the layout, masonry and open-panel timber frame cope best. With SIPs and closed panels, make the decisions before you order.
5. Embodied carbon
Timber stores carbon, so timber frame usually has the lowest embodied carbon of the three. SIPs add a foam core, which carries more embodied carbon than mineral wool or wood-fibre insulation. Cement-based blocks and mortar give masonry the highest figure. Whichever you choose, ask for FSC or PEFC-certified timber and board.
6. Site and access
Panels arrive on a lorry and often need a crane. On a tight Oxford street or a garden plot behind a terrace, that can mean a road closure or smaller panels. Blocks and bricks come in small loads and can be barrowed in, which is why masonry is still common on cramped sites.
7. Who will build it
SIPs and timber frame are usually put up by the manufacturer’s own team or an approved installer, and the builder does the groundworks, roof finishes, services and fit-out. Book panel suppliers early, because lead times can run to weeks or months.
8. Whole-life cost
Cost per square metre is only the start. Add the running costs of the finished home, the saving from a shorter programme and any extra ventilation or airtightness work the new rules call for. Get your structural engineer, energy assessor and builder together before the design is fixed, so the structure suits the U-values, ventilation and solar panels you need.
Which method suits which project?
- A single-storey extension to a brick house. Masonry is simple and matches. Timber frame with a brick outer leaf is quicker.
- Building upwards, over a garage or on poor ground. Timber frame or SIPs, because they’re light.
- A new home aiming for Passivhaus. SIPs or closed-panel timber frame.
- A tight urban site with poor access. Masonry, or timber frame made in small panels.
- A conservation area or the Cotswolds. Any of the three. The planners care about the outside, and stone, brick or render can go on any structure.
Summary and next steps
There isn’t one best method. Timber frame is usually the cheapest and goes up quickly. SIPs cost a little more and give the fastest, most airtight shell. Masonry is slower but suits small sites, late changes and buyers who want brick. All three can meet the Future Homes Standard. What matters most is that the insulation and airtightness are built as designed.
If you’re planning a new home or an extension, talk to us before the design is fixed. See our new build homes across Oxfordshire and house extensions in Oxford, or get in touch.
Frequently asked questions
Is SIPs cheaper than timber frame?
No. A SIP build usually costs a little more per square metre than timber frame, often 5–10% on the whole build. The quicker programme and lower heating bills can win some of that back.
Is SIPs cheaper than brick?
Not by much either way. Whole-build costs per square metre overlap, so the difference comes from the programme and the site. SIPs save weeks on site, while masonry suits tight access and late changes.
What are the disadvantages of SIPs?
Design decisions are fixed at the factory, so late changes are slow and costly. The OSB facings must stay dry, both during the build and in use. The panels usually need crane access and an approved installer, and lenders and warranty providers look for a BBA-certified system.
What is the typical lifespan of a SIP house?
BBA certificates for SIP systems give a life of at least 60 years, provided the building stays weathertight and damp-proof. Warranty providers expect the same 60 years from any structural system, and a well-maintained house lasts far longer.
Can SIPs be used with timber frame or masonry?
Yes. A common mix is a SIP roof on timber-frame or masonry walls. It gives a warm roof and leaves the roof space open for a room in the roof.
How does the Future Homes Standard affect my choice?
All three methods can meet it. It comes into force on 24 March 2027 and asks for solar panels, low-carbon heating and tighter airtightness. Systems that are reliably airtight, such as SIPs and closed-panel timber frame, carry less risk at the final air test.
Will my local builder work with SIPs?
Most good builders will. The panels are usually put up by the manufacturer’s team or an approved installer, and your builder does the foundations, roof finishes, services and fit-out. Agree who is responsible for airtightness before work starts.
About the author
Henry Lynch, Director, Lynch Brother Homes
Henry is an Oxfordshire-based builder with deep experience delivering high-performance homes across SIPs, timber frame and traditional masonry. His focus is on fabric-first design, airtightness and practical detailing that lasts, balancing programme, cost and carbon.
- Location: Oxfordshire, UK
- Specialisms: New homebuilding and eco-friendly building practices
- Years active: 15+ in UK residential construction
Company profile · Contact Henry · LinkedIn
Sources: Approved Document L 2026 (GOV.UK); Structural Insulated Panel Association; Structural Timber Association; NHBC; BBA certificates for SIP systems; UK build cost guides, 2026.
