Raft

Raft foundation details, including a set showing an insulated foundation system with almost every wall type: masonry cavity (full and partial fill), externally insulated masonry, brick and block faced timber frame, timber I-beam, SIP, CLT and ICF walls, with and without ring beams, and a timber frame party wall. There’s also a timber frame wall on a reinforced concrete raft and a Passivhaus raft wind-tightness detail.

Why use an insulated raft? Insulating below and around the raft keeps the slab on the warm side and reduces thermal bridging at the wall-floor junction, which is useful on low-energy projects.

Is there guidance on insulating foundations? Yes. See our article Insulating Foundations.