Correct placement of insulation in isolated floor

OK, I know I've asked this one before (in my studio build on studiotips as well!) but I haven't had a response yet. So I thought a change of subject line might be worthwhile... please slap me if I'm wrong :oops: Anyway, can some enlightened soul please give me some advice as to where the best position for thermal insulation in an isolated floor is? I have two options: 1. Under the foundation slab 2. On top of the foundation slab but with a flooring screed on top of this and on top of that the wooden studion floor. My architect for simplicity sake has proposed the insulation under the slab but with a strnge 'supporting' arrangement for the inner floor (essentially, to me, a floated floor) The insulation material is either extruded polyurethane or expanded polystyrene. FWIW I have read Rod's book (essential in discussions with the architect) and the proposed studio structure is as follows: Inner room: 100mm HD concrete block with concrete beam and block roof Outer room: 140mm HD block with wooden frame pitched roof, spaces between beams infilled with plasterboard. There will also be a ventilation system. A structural engineer has also been consulted and will ultimately 'sign off' the structure so everything is above board and legal. Hope someone can help me soon as I'm putting in building warrant applications as we speak! :shock: The studio will be detached from the house although is relatively close (~4m) to neighbours.

diziet wrote:

Anyway, can some enlightened soul please give me some advice as to where the best position for thermal insulation in an isolated floor is?

Under the slab..........

My architect for simplicity sake has proposed the insulation under the slab but with a strnge 'supporting' arrangement for the inner floor (essentially, to me, a floated floor)

diziet, could you have your architect email me a section through what he is proposing to do - we all know that wood decks do not isolated floors make..... I would like to see his details...... [removed] Rod

Rod the information should be with you now. Thanks so much for looking at this... :D :D :D :D :!:

diziet wrote:

Rod the information should be with you now. Thanks so much for looking at this... :D :D :D :D :!:

diziet, not as of right now it isn't. Perhaps he should resend it Sincerely, Rod

I emailed it to [removed] - two attachments. Shouldn't really take that long though :? I'll try a resend from my other email account.

diziet wrote:

I emailed it to [removed] - two attachments. Shouldn't really take that long though :? I'll try a resend from my other email account.

Sorry, I had a typo - the @ became a 2 - it's corrected above - [removed] My mistake completely, PLease correct and resend. Rod

Info on it's way to you now Rod :roll: Let me know if you need anything else

diziet wrote:

My architect for simplicity sake has proposed the insulation under the slab but with a strnge 'supporting' arrangement for the inner floor (essentially, to me, a floated floor)

diziet, you are sooooo mistaken here......... there is no floating floor - regarless of whether it seems essentialy to you that there is). He's pouring a sand mix concrete (50mm) directly on top of your concrete slab (150mm) I don't have a problem with his design - it gives you a larger heat sink to help lower your heating costs. Rod

Rod, thanks for this! My main concern was the inner found supported (at it's outer edge) on the outer found with the insulation between. Not being completely sure of the properties of extruded polyurethane insulation I though this arrangement would provide a flanking path between the inner and outer foundations. I'll look forward to telling my architect the good news! On a slight downer the local council have told me the plando not meet building regs - no other info at present so there will need to be some slight changes to the construction somewhere (nothing too major I hope). Aprt from that my wife is due to give birth on Monday so the studio build will take a back seat for a wee while... Thanks again Rod, your reassurance is much appreciated.

diziet wrote:

I'll look forward to telling my architect the good news!

.diziet, congrats on the baby - As far as the design goes - the only thing i don't really like is that the slab doesn't thicken up (haunch) under your inner wall assembly........ That is my only concern Rod

Agreed Rod, I had originally specified the haunch myself. However my architect did apparantly discuss his design with a structural engineer. At some point in the future the SE will be required to 'sign off' the design so this problem will be taken care of. I'll let you know how things progress. PS no baby yet!

diziet, I know nothing at all about building codes in Scotland - but here in the states the building code will not allow a footing 5" thick to carry a load bearing wall assembly. I'm real interested in what comments your engineer has about this......... Please keep me posted. Sincerely, Rod

Isla Grace was born on 28th May - a beautiful wee girl!! So things have been a bit hetic in our house to say the least! Still, I've managed to get a building warrant and am awaiting quotes from builders - hopefully work will get started in October.... Rod, this info is for you as requested... I spoke to the Structural Engineer direct. He has suggested that the founds use A252 mesh rather that A142 (8mm rather that 5mm I think) but said that the depth of foundation for the inner room was OK. Unless... the ground is clay or near trees in which case the min over all depth (inner found+insulation+outer found) be 600mm rather than 450mm. He did some calcualtions while I was speaking to him to check the depth and was quite happy with it! He has suggested perhaps installing dowel bars between the inner and outer founds in case of differential settling but I've vetoed that on because of the effect on sound isolation. Hope I've made sense of this info, I can email his revised drawing if needed. All the Best S