Carp07

Two drawings showing (ignore the first can’t seem to edit it away) under slab insulation and over slab insulation (dpc under timber frame)

In my head how insulated above slab will look though maybe move wall to edge of slab so got to decide which

I'm still unsure to be honest on slab design, either insulation above or below concrete slab (obviously original plan is below albeit OTT)... so either 150mm insulation below slab or 100mm insution above (i know its different types of rigid insulation also). I thought with slab (with insulation above) you are suppose to go 50mm bigger than where you plan to sit your wall plates for strength or does that not matter as its reinforced concrete slab - plus the external batten then cladding will take up the 50mm anyway. Im just looking to get max headroom and i know you suppose to bring your finished floor up 150mm above ground (got to stay below 2.5m) The wall design i'm definitely going to go with insulated 89mm timbers with service batten on inside.

Oliwoodings, yes that’s definitely what Ives been looking at for concrete floor… concrete then insulation on top. Did you do your slab level with ground then end up with 150mm ffl above ground? The walls this is also pretty much my thinking 4x2 insulated with pir, service batten then fire board inside and batten then cement board cladding outside. Oh and yes I’ve watched a few of those oak wood garden room videos. As I’ve had to go through planning (new build home) will have to see what they say about change of slab and wall design, as said before building control seems okay with it but planning could be different, maybe

I would have thought regular use for 2 - 4 hours at a time… want it to be able for use in summer & winter

Yes the whole thing the more I look online feels like a copy and paste job with like you say one site conveniently having all listed. Way over engineered too and is giving me a head ache. My view to the wall profile is as attached with 90mm rigid insulation inside timber frame then service batten & 15mm board. Building control said the architects drawing looks “robust” lol! I briefed him that I didn’t want to spend the earth too. Cost me £600 so far for his services which also includes submitting planning application. Back to the base, my original thoughts were to having 100mm mot, 20 - 50mm sand blinding, 120 pir insulation with 100mm concrete slab to top with which the timber frame would sit… But I don’t think this works and you need ffl 150mm above ground level which eats into head room to stay under 2.5m… so my current thoughts are as my drawing.

It’s what my architect designed, personally I feel it’s over the top… you reaction says to me like “wow your going passivehouse for a garden room!” It’s 400mm away from boundary, spoke to building control and as long as fire ratings met of timber frame (so cement board cladding externally and 15mm fire board internally it fine). so you reckon a reinforced slab? With insulation under concrete slab but just say 120mm pir rigid board with concrete over top? Or slab then insulation on top with floating floor? Thank you for reply

Hi, I’m not sure how to introduce but I’m just going to blurt it out… looking at doing a garden room and my architectural technician has designed a raft foundation for me but I still seem to be at a loss on how to go about it. the raft foundation design to me seems OTT for a timber frame garden room but then this is not my area of expertise so…. Advice please. to me it looks like 150mm insulation under the raft going to 100mm under where perimeter frame sits (with concrete going other way 100mm to 150mm). Any advice would be most appreciated