Tai ar y Cyd Pattern Book
Developed in partnership with 23 Welsh social landlords, and with support from Welsh Government, the Tai ar y Cyd Pattern Book provides a practical framework for delivering cost-effective, ultra-low carbon housing at scale.
In response to escalating housing demand, fragile supply chains, and urgent net zero commitments, the Pattern Book introduces 15 core house types and 18 variants—from one-bedroom flats to fully wheelchair-accessible homes—each meeting or exceeding Welsh Development Quality Requirements and the Welsh Housing Quality Standard.
Shifting the narrative on standardisation
Standardisation in housing often evokes thoughts of bland repetition and design compromise. The Tai ar y Cyd Pattern Book turns that idea on its head with a placemaking guide that helps local authorities and housing providers tailor developments to their community’s context.
The homes follow a robust, fabric-first approach with two performance levels: a baseline aligned with AECB CarbonLite standards, and an enhanced version targeting full Passivhaus Classic.
Key features across all homes include:
Timber frame construction promoting Welsh-grown, sustainably sourced timber
Bio-based insulation and airtight detailing to reduce embodied and operational carbon
Renewable energy integration, such as PV panels, air source heat pumps and MVHR
Carefully modelled daylighting, overheating and air quality standards
Layouts that prioritise future adaptability and long-term affordability
Together, these features help tackle fuel poverty, lower carbon emissions, and create healthy, comfortable, and long lasting homes.
Supporting local supply chains
Just as important as what the homes are made from is where those materials come from.
The Pattern Book seeks to promote the use of Welsh-grown timber and natural insulation —cutting embodied carbon while reinforcing local supply chains.
These choices help root each development in its setting, echoing the materials and textures of Welsh towns and rural communities— a similar approach was seen at Gwynfaen, a development of 144 timber frame homes.
Inspiring systems change
Beyond technical standards, the Pattern Book looks to drive broader industry change. Designed for offsite manufacturing using Category 2 Modern Methods of Construction, the ‘kit-of-parts’ approach reduces waste and transport emissions, supports local skills and employment, accelerates delivery, and provides greater cost certainty. It also offers a scalable, replicable framework that’s adaptable across regions, and simplifies compliance with Social Housing Grant funding.
One example, Celtic Offsite—a social enterprise that manufactures timber frame homes—plans to use the Pattern Book to improve manufacturing efficiency for faster delivery of affordable homes across the country.
Tai ar y Cyd represents a significant step forward in our commitment to building sustainable and affordable homes here in Wales. This innovative pattern book gives developers the tools they need to build homes more quickly and deliver against our target of building 20,000 affordable low-carbon homes by the end of this Senedd term.
Jayne Bryant, Cabinet Secretary for Housing and Local Government
A foundation for future innovation
The Pattern Book is already in use by Welsh housing associations and has sparked interest from partners across the UK looking to replicate the model. Welsh Government views the book as a key tool in its ambition to deliver 20,000 affordable low-carbon homes by the end of the Senedd term.
And this is only the first step. Future phases may explore higher-density typologies, more urban-friendly layouts, and routes to pre-approval that could further accelerate uptake.
To learn more about the Pattern Book and house types, and request a copy of the guide, visit TAYC: Timber-based affordable homes for Wales.
