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Acceptable Construction Details




The details in this section have been developed for hollow concrete block construction. Details are given for the junction with a range of roof, ground floor and internal floor types, as well as at external wall opes.

The details are indicative. They focus on the issues of thermal performance and air tightness. Other issues are not considered fully. Insulation thicknesses for the main building elements have not been provided, as these depend on the thermal properties of the material chosen, as well as on the desired U-value.

Due to the practicalities of fixing insulated dry lining to blockwork, depending on insulation restraint, board thickness, boards should be fixed according to relevant certificates.

These diagrams illustrate good practice for design and construction of interfaces only in respect to ensuring thermal performance and air barrier continuity. The guidance must be implemented with due regard to all other requirements imposed by the Building Regulations.

A vapour control layer should be installed on the warm side of the insulation to minimise the risk of interstitial condensation on the cold masonry behind the insulation. Care should be taken to avoid gaps in the vapour control layer at all joints, edges and service penetrations. A services cavity on the inside of the insulation can be used to facilitate fixing the insulation, allow the vapour control layer to be inspected and for services to be run without perforating the vapour control layer.

Where theses details are used for the Target U-values and constructions described in Table D6 of TGD L 2021 the psi values published in Table D6 may be used to calculate the actual thermal bridging heat loss 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.

The 2021 edition of the ACDs updates the drawings to take account of industry practice. The performance requirements remain the same as for the 2011 edition.

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