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Acceptable Construction Details




The details within this section are valid for a range of timber frame wall thicknesses. Details are given for the junctions with a range of roof, ground floor and internal floor types, as well as at external wall opes.

A variety of structural forms can be adopted, with variables such as stud centres, double or single head plates. The form of structure influences thermal performance, and must be taken into account when using these details.

Insulation thicknesses for the main elements have not been provided as these depend on the thermal properties of the materials chosen together with the proposed U-value. Further variables are insulation and sheathing types, plasterboard type and thickness, internal linings and external cladding. Details are shown with a masonry outer leaf for simplification. Other cladding may be used without loss of thermal performance or increased technical risk subject to suitable detail. All materials and workmanship are to be installed to Technical Guidance Document D "Materials and workmanship".

These diagrams illustrate good practice for design and construction of interfaces only in respect to ensuring thermal performance and air barrier continuity. Other issues are not considered fully. The guidance must be implemented with due regard to all other Building Regulations requirements.

Where these details are used for the Target U-values and constructions described in Table D4 of TGD L 2021 the psi values published in Table D4 may be used to calculate the actual Thermal Bridging heat loss for a dwelling for the key thermal bridging junctions in that dwelling.

Technical Guidance Document B and Supplementary Guidance to TGD B provides guidance in relation to the provision of cavity barriers in air cavities, cavity barriers within combustible insulation layers and fire protection of structural elements.

Refer to I.S. 440 for requirements for materials, design, manufacture, construction details, site work and quality control for platform timber frame construction.

The 2021 edition of the ACDs updates the drawings in the 2011 ACDs to include internal insulation which was previously provided for in the text. The performance requirements of the 2021 ACDs remain the same as for the 2011 edition.

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