New Details for October 2025: Masonry Extension Full Fill Wall Types

This month we’re expanding our collection of masonry wall extension details with a comprehensive new set that explores full fill cavity wall construction in combination with a range of floor types and finishes.

The series includes 14 new details (DL471–DL484), each focusing on typical construction junctions for single-storey extensions using 100mm full fill PIR cavity insulation. These details are designed to support envelope design, with U-value of 0.18 W/m²K.

Both brick and rendered finishes are included, along with beam and block, ground bearing slab, and suspended timber floor options. Roof interfaces cover flat roof, pitched roof, cold roof, and warm roof build-ups — ensuring you can coordinate junctions effectively across the whole envelope.

What’s included:

• Full Fill Cavity Wall with Beam and Block Floor
• Full Fill Cavity Wall with Ground Bearing Slab
• Full Fill Cavity Wall with Suspended Timber Floor
• Full Fill Rendered Cavity Wall with Beam and Block Floor
• Full Fill Rendered Cavity Wall with Ground Bearing Slab
• Full Fill Rendered Cavity Wall with Suspended Timber Floor
• Full Fill Cavity Wall to Eaves – Cold Roof
• Full Fill Cavity Wall to Eaves – Insulation Between and Under Rafters
• Full Fill Cavity Wall to Cold Flat Roof Eaves
• Full Fill Cavity Wall to Cold Flat Roof with Existing Pitched Roof Abutment
• Full Fill Cavity Wall to Cold Flat Roof – Existing Wall Abutment
• Full Fill Cavity Wall to Flat Roof Parapet Detail
• Full Fill Cavity Wall Window Head and Cill Detail
• Full Fill Cavity Wall Window Jamb Detail

Why full fill?

These details are ideal for straightforward construction in low-rise domestic extensions. Using full fill insulation in the cavity allows for a reduced wall thickness compared to partial fill systems, making it particularly useful where space is limited.

As always, these details are intended as a starting point and should be coordinated with your project-specific requirements.

New Details