Can a raft slab be extended later for a home addition?

Yes, in principle — an extension typically involves a new slab section properly joined to the existing raft slab, following the same general approach used for extending any concrete slab, with appropriate joint design between old and new.

Your engineer needs to assess both the existing slab’s condition and how the new section will structurally interact with it, since new concrete doesn’t bond seamlessly to old concrete as one continuous structure.

This is exactly the kind of project that genuinely benefits from involving an engineer early, before the extension’s design is finalised, to ensure the new and existing sections work together properly.

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