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Building Regulations: Walls below ground level

Depending on whether the foundation has been cast as deep-fill or shallow-fill, there could be a small or large amount of wall construction needed below ground level (substructure), on which the above ground walls (superstructure) will be built. 

The principal requirement of the substructure is to ensure adequate support is provided to the superstructure. To remain effective the bricks or blocks and mortar should be resistant to frost and also to sulphates within the ground.

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      The Planning Portal is delivered by PortalPlanQuest Limited which is a joint venture between TerraQuest Solutions Limited and the Ministry of Housing, Communities & Local Government (MHCLG). All content © 2025 Planning Portal.