Block and beam for timber frame aiming for passivhaus

[marmic]

block and beam in + course of 140mm marmox thermoblock (have a few left over to be ebayed!)  + 2 courses of 140mm coursing bricks directly above 140mm fundation blocks below beams - ready for timber frame (larsen truss) soleplates. DPC wrapped up from under beams and will be lapped and sealed over top course with DPM which will be directly on beam and block. Then 150 or 175mm PIR (2 layers joints staggered and taped) + vertical upstand sections to screed level. Membrane over, open zone UFH pipes, 50 or 75mm screed. Outer skin of block/brick just to look nice and holding 75mm extruded insulation and sub-floor vents. Also keeps 'ground' away from supporting walls. Once timber frame installed the gap over bricks and 'foundation cavity' insulation will have horizontal section of extruded polystyrene - maintaining gap to underside of larsen truss and then sealed with precompressed tape.  Then timber cladding...................

BCO/structural warranty company happy.........

[Great_scot_selfbuild]

On 15/02/2025 at 13:04, marmic said:

good afternoon, would be very interested if resolved and what the conclusion was please? I see things went off topic a bit!  We are using a larsen truss system (ie all the load on inner 140mm stud) and have to have suspended floor due to heavy clay, trees, hedges. We are at passivhaus high performance (won't quite meet certified due to form factor - not huge and single storey). Current plan is preinsulated planks (avoiding screeds etc) with timber frame sitting directly onto edge - so almost replicating a raft, but suspended.  But getting very nervous due to long delays with design for coordinated drawings and building control, therefore now urgently exploring other options. Seems to be a few beam & EPS products out there - but how to detail edges with no traditional masonry/brick, where to sit timber frame, and prevent/minimise thermal bridging.  Plus dpc/dpm/ventilation detailing..................  kr.........ma

@marmic interested in your build - sounds like we’re working around very similar challenges. We’re doing a suspended steel ring beam with b&b and then a timber frame (Larsen Truss) on top.