SBMS

Possibly a stupid question that demonstrates my lack of understanding but… is a VCL required or recommended on a masonry cavity wall, and if not why not? Speaking mainly about an EPS bead full fill cavity. I sense not, and my guess is down to the wall makeup versus timber frame where the vapour permeability goes from low to high to encourage ‘drying out’.. does this principle not apply to masonry? Or just not to the same amount?

Interesting... guy from warmcel told me we needed a very vapour impermeable layer for the inner roof makeup (Propassiv best - OSB cheapest) but said we couldn't use Plaster board (and that the pressure from the Cellulose blower could blow it off). Is that rubbish?

If you did it again would you try and get them to fill before plasterboard has been fitted?

Would you recommend cellulose again? How deep did you go?

Thanks @Duncan62. Any reason you went wood fibre over cellulose?

Was that a full fill? What U Value did you achieve with that?

Thanks Liam. When was that? Did they give any additional costs for 300mm or higher?

@Kelvin Did you ditch the idea of cellulose? What did you go for?

Currently assessing a blown cellulose product for our attic rooms and roof.. Anybody got any recommendation on suppliers/installers? So far have found Warmcel (awaiting call back) and Thermofloc (made by Thermafleece). Thermofloc tell me they're no longer doing blown cellulose installation. At the moment am considering switching to another blown product for the roof (such as blown mineral wool) purely because of the lack of installers (we're not DIYing it). It does make me wonder how common a product it is, outside of this forum (and the use of MBC, which is across this forum and where they use cellulose extensively, but presumably install it using their own teams?) Anybody got any recommended installers? UK, north west.

Got you. Useful to know whilst we are pre drawings stage. Does anyone else know if this is a common ask with cellulose blown roofs?MBC profile doesn’t seem to have a 50mm ventilation gap.

What were they asking for?

@JohnMo great pictures and explanation thanks v much. What u value did your roof makeup achieve? Did you consider keeping your 256mm rafter depth and using an insulated plasterboard - and if you did how come you decided against it? Is 256mm the maximum posi rafter depth or could you have gone deeper? @Iceverge if we went blown cellulose what depth gets us to 0.1? I’m thinking of doing what John did but either increasing the depth with counter batten, or lining with an insulated PB to get to the u value.

What is your airtight detailing at the wall plate?

Thanks @Iceverge. Would posi rafters be able to span from the ridge to the wall plate without a purlin (or supporting upright like an attic truss). With rooms in the roof/ part vaulted ceiling that would provide a better internal aesthetic.

Would trusses be out due to the intersecting roofs? Do you think posi rafters could work?

Was yours an ICF build?

Thanks @SteamyTea @Iceverge would you ever recommend this plus an insulated plasterboard? I know you seem to favour Rockwool if more insulation is needed? Still intrigued that no one has advocated SIPS?

Just for reference, this is the elevation with some measurements for the roof sections:

Thanks @JohnMo - really interesting. A portion of our roof is vaulted and the other portion isn't - how would you incorporate a second floor in that instance? Would it preferable to hang it from the internal block, or sit it on the wall plate, and then sit the posi joists on top of the floor?

Posi Rafters look interesting... They'd be useful for the vaulted section. Do they typically rest on a ridge beam and purlins, without the need for a bottom chord?

Thanks @Iceverge - any reason you'd discount SIPS? Will Elevations drawings suffice?

We're in the process of putting together a design spec and discussions with the architect for our roof construction method, and insulation. We have a 2 storey house, with rooms in the roof, and one part of the roof is vaulted from the first floor to the roof (so no bottom chord on that part). We have a bit of balcony overhang as well. We've decided to go traditional brick and block with a 200mm cavity with EPS beads. There are two primary construction methods we're looking at for the roof: SIPS roof Engineered attic trusses Both options probably require a steel ridge beam, although SIPS might get away with a glulam ridge (and glulam purlins - which are a nice feature exposed in the rooms). SIPS roof A local SIPS company make a 195mm SIPS panel which achieves 0.13 u-value, so this plus a 37.5mm insulated board, or even higher would get us the U-value needed. No issues with having to be accurate with insulation. Makeup is relatively slim @ 200mm as well. The primary negative that I have seen for a SIPS roof is complaints of increased noise, particularly when raining. Is this others' experience, would a 195mm panel reduce this, and is there an easy option to mitigate if it is? Engineered trusses If we go the engineered truss route then we have some decisions to make regarding how we insulate it. I've put the commentary (mainly negatives) underneath each insulation method: A 150mm PIR board between the joists (either with or without an air gap dependent on membrane) with an insulated plasterboard underneath would get us to 0.1 Concerns regarding fitting - we could use gapotap, but timber can shrink and there are fiddly bits around the wall plate junction to ensure thermal bridging is minimal Blown in cellulose (with or without an insulated plasterboard underneath?) No real concerns with fitting, but would potentially need a much deeper joist? I don't know what a 200mm cellulose U Value gives, we could possibly go for deeper joists but then we're losing headroom potentially inside Blown in EPS Beads (with or without an insulated plasterboard underneath?) Same as cellulose but probably the same questions/concerns - however easier as the walls are going to be EPS beads the same firm could do it Rockwool/mineral wool batts (again, probably would need an insulated plasterboard underneath) Would be fitted by hand, so would need to be on top of the fitters Spray foam is OUT - so will not use for reasons that have been done to death on this forum Has anyone any advice or feedback on the above, their experience, and what they would look to do? Thanks in advance

Absolutely. Fairly unlikely your architect has the same deep knowledge of local planning, planners themselves, cases they can reference etc that a planning consultant has. I would speak to a consultant and briefly give them your idea of what you want and if it looks like a go-er engage an architect to draw up your design, perhaps prepare the design and access but get the planning consultant to submit your application along with the planning statement. They’ll do things like find and reference similar applications that were passed recently, cite proper planning policy in detail and - at the end of the day present your application as serious and professional. Planners won’t want to risk rejecting an application if it’s policy compliant in the event you appeal (and win). Most councils are nearing broke and expensive appeals costs are a priority concern for councillors that sit on planning committees. Good luck!

I would speak to a planning consultant that’s got a good history of applications with your local council. They will probably know the planners and might even know the planner that made the determination for the current application - it’s likely they would be assigned if you went in for another application. The consultant would have a good view of what the planner might say. Design can often be very subjective so can come down to the planner assigned. Also - read the current report from the planning officer and see what weight they gave to the design elements - if they called out how it was suitable as a traditional design for example it might give some insight into how much weight they gave it. I would recommend you definitely pursue the design you want; in the context of what you’ll spend on the build it would be money worth spent - especially if it’s not a design you’re particularly happy with.

Garry this seems really expensive. Is your design particularly complex and/or are you paying London prices?