Annker

Yes you certainly will need temporary support of the external leaf. That is a significant opening and if I understand correctly has two storey of brickwork above it. Similarly I'd question supporting the inner leaf by solely propping the existing joisting. Sounds to me like a job for needles penetrating both leafs.

Thanks for the response. I know you have posted a lot on the subject and believe me I have read reams of material on the subject and still can't confirm my spec! Agreed that hygroscopy may be an issue with gypsum and my initial thought was that gypsum could not be used in vapour open system but as my original post it is a recommended detail from Back to Earth. Surely given where the PB and skim layers are located in the build up condensation should not be an issue. Modelling shows the Dewpoint within the insulation albeit it is towards the warmside; perhaps you saying the concern is if the Intello membrane allows vapour to travel outsode to inside should relative conditions drive it so?

Dear all, I am looking for some design critique on a IWI design which I am planning to install in my Victorian semi-d renovation project. The existing walls are 9" solid brick with original lime mortar jointing and the house is sited in a relatively sheltered urban location in Kent. Following weeks of reading the wide array of opinions regarding installation of IWI to a solid walled house I have arrived at the buildup below with two different insulation options: Internal to external Breathable paint finish Gypsum skimcoat Gypsum Wallboard 12.5mm Service cavity 38mm x 50mm battens @ 400mm c/c Intello plus VCL 60mm Breathable Insulation layer OR 60mm PIR foil backed Insulation/VB layer 225 solid brick wall *Existing The design follows the "warm batten" arrangement. Preference is for a vapour open design and use breathable insulation, however I am unsure what specific type product could be used in that instance. I imagine the insulation would need to somewhat resist compression from the battens so perhaps batt type format. HAs anyone used a glass or mineral wool slab in a similar situation? Wood fibre is a candidate but it is pricey. I believe a vapour closed design has more risk in terms of trapping moisture within the buildup, however PIR insulation with its relatively high compressive strength lends its well to the warm batten design so this option is easier to spec material wise. After much reading I am satisfied that a gypsum plasterboard and finishing coat can provide a satisfactory degree of vapour permeability, hence their inclusion. Some will disagree (some who worship at the Lime Alter will be horrified) however there are studies that suggest that gypsum is more "breathable" than lime. I actually spoke to a tech/sales member of staff of a well known eco & natural BM and he (of his own accord) said he regards gypsum as entirely suitable in some IWI system build up, in fact they have it specified in some of their IWI solution on their website.

Exactly this. Sure the entire world is sitting on liquid molten material and its going nowhere (save a few earthquakes!)

10mm gap along both plywood to plywood junctions and the perimeter of the room. Plywood doesn't expand along the length or width of the sheet to any degree that requires consideration in this scenario. I used Hardwood faced ply as opposed to softwood faced shuttering ply. In the absence of the floor having any direct fixing to the underlying substrate, it is prudent to lay up the subfloor with materials that remain general flat rather than warp if you look at it sideways like shuttering ply The floors I was installing were generally all hardwood T&G flooring, secret nailed and occasionally may have some inlay work. And for that particular installation I would rate plywood above OSB. I feel plywood has a more robust surface for installation; nailing, marking out on etc.

I've installed hardwood timber floors in many houses using the floating floor method and it performs exceptionally well. I actually revisited a house over christmas where this was done in 2006 and the home owners reported the floors are as stable as the day the were installed, I believe 17/18 years is a sufficient test duration! I believe the buildup was: 18mm oak T&G boards 12mm hardwood ply (laid half bond at a 45 degree and screwed to the ply layer below) 12mm hardwood ply (laid half bond and loose over the PIR) 120 PIR Sheet DPM Concrete subfloor

Caberdek is sound for laying the tray on. The joints are susceptible to water damage, however looks like they have been jointed with PU glue so that largely negates that risk.

@jayc89 I'm back reading this thread and informative as it is still remain none the wiser and undecided regarding which IWI build up to use in my house refurb, with existing walls as yours. Did you complete the job yet? IIRC reading another thread you did opt for the warm batten/PIR and gypsum build up. If so can you let me know how you eventually settled on that particular build-up and how it is performing?

@Keeko Interested to know how you got on with the floor insulation job?

Project isn't a refurb it's a full strip out renovation and extension (cost~£250K), regardless the whole idea behind the thread is to use this software to do what a QS would. There isn't a builders merchant in the country that would spec and build out a quote for the job.

Ah come on we aren't in Venezuela economic territory yet! Regardless, professional Estimators face the same issue and it is simply handled with a % inflation factor built into the forecasts.

I just wanted to share/hear user experience of a pricing/estimating software I've found as I believe it could be very useful to members of the forum. A essex small builder I follow on youtube uploaded a video using it to price an extension and I was amazed by it. It's called Price a Job. Additional it can do structural calculations and other PM tasks but it is the estimating module that I find interesting. First off to say I have zero connection to the company. The company behind it may be connection to Canada, the developer may be east european, the website looks basic but the software is very good and wholley tailored to the UK. I don't yet have a subscription to use it but I think I will sign up for a month to put a cost plan together for my victorian renovation and extension. You basically model your building in the software similar to doing so in sketch up but it has a drop down menu to assign a material selection for each element and each material has a UK market rate cost assigned to it, I think prices are updated weekly. I don't know how that is done or how accurate the prices are but you can input your own rates if preferred. Similarly labour cost are calculated for the construction of each element. Once the model is completed so is the price estimate. Perhaps there are other companies that I am not aware off offering similar software but I wasn't aware of this until the youtube builder demonstrated it. I imagine it been developed for builders to put together quotations but I believe it may be a great way to price up a single project as there is no 12 month commitment. Interested to hear what other think of this software.

Thanks again for the feedback. Yes reducing the depth of the service cavity is certainly a strong possibility as the TF will comprise of an office and a bedroom, as such there will be fewer services to accommodate vs say a kitchen or bathrooms. Noted also regarding continuity of membrane at joist level. Although the set back of the band joist (aside, I would term rim joist) is not an arrangement I've seen previously. I guess the sheathing continues over the insulation at that point to ensure both the GF and 1st floor TF panels are tied together. I think lining the respective studs through and strapping with 1000mm galvanised straps would be required also.

@Iceverge I didn't initially realise that your pdf sample build-up was from an interactive tool and free to use. It's a great bit of software, I don't have German to understand some of the descriptions but thankfully numbers and values are same in both languages! I've played around with the buildup and came up with design that in separate components makes sense to me and I would be very comfortable delivering onsite but I'm not certain it works all together though. The 140mm mineral wool within the studwork makes up the bulk of the insulation, and, vs. PIR, ticks the box for breathable and acoustic performance. Overboarding studwork is 60mm PIR in large format boards tends itself well to be the insulation choice to be fixed uninterrupted over the studwork, and it also deals with cold bridging spots. (Perhaps this will be reduce to 50mm or 40mm thickness) This PIR layer could be tape and may be sufficient to provide a VCL but for the minor additional cost I've chosen to spec a sheet VCL 40mm service cavity internal to the wall construction proper (will likely be formed with 45mm battens) 11mm OSB behind the plasterboard to give a frimer wall finish, especially as I have the studwork @600mm c/c @Iceverge You assigned "Rear ventilated level (outside air)" to the cavity in your model; I have simply copied you in this. How did you know to assign that particular selection to the cavity, its illustrates battens in the model which I don't believe should be there in reality. Insulation_of_TF_1.pdf

Another vote for the reolink. A client had one on his project and it was a great piece of kit. I've started my own project now and will buy a reolink myself. That £4p/m sim was a great deal pity its no longer available. Still the O2 sim at £50 p/a ain't too bad I suppose

Hi Iceverage, ATM my target u-value is TBC. Rightly or wrongly, I had in my head to get the structural arrangement figured out and then size insulation thicknesses/type accordingly to meet the confirmed u-value target. My project is chiefly a renovation of a victorian semi-d with an 2 storey TF extension; the ground floor will be an office and a bedroom will be above on the 1st floor. As such it is a relatively small extension, there are only 4no windows so I can easily design them to opening either inwards or outwards. I have actually flicked over that pdf before, I think you had it attached to a previous comment in another thread. I had discounted its design (omission of vcl) as it added more choice/questions/queries all which lead me away from making a decision. I suffering badly from analysis paralysis, and I will never get the thing built if I continue this way! I note that the internal finish is lime-gypsum plaster. Is that an actual product? Lime makes sense as it provide good breathable characteristics required in that design; in contrast to gypsum so that's a little confusing. Also is there doesn't appear to be a service cavity? Appreciate that there isn't a vcl to protect but I have always liked that the service cavity provides some manner of containment for cabling. You make good points about PIR from an acoustics performance perspective, and that PIR foil faces introduce additional (potentially moisture trapping) layers. I have specific concern about that in my initial design.

Yeah I previously used 11mm osb but had read 9mm as being sufficient and commonly used, irrespective of that I probably will still use 11mm as the extra cost of 11mm vs 9mm on a TF of this scale is minimal. Again, on my previously built TF I too kept all insulation within the studding & service cavity, however my research over the past day has pointed toward adding insulation external side of the breathable membrane and osb, commonly termed "cavity wrap" The rationale is that insulation in this position is not interrupted by studwork therefore, continuous and goes some way to reducing cold bridging. It makes sense to me, although there must be a specific wall tie required to tie the TF to the brickwork, I'm yet to look or find it. Why do you use osb internally, certainly it would create a very solid wall but it adds a significant chunk to labour and material cost, are there other benefits? Given the service cavity would internal side of that osb layer it doesn't provide patressing either, at least not in my build-up arrangement.

Hi all, I'm at building reg design phase for my planning permission granted victorian refurb and extension. For context I am a carpenter and I have done a couple of stick frames previously but not in the past decade, therefore I would appreciate critique of my preliminary TF design before I sit down with my SE and Architect. From external to internal: 100mm brick external leaf 50mm cavity 25mm-50mm PIR insulation (Thickness selection TBC to achieve yet to be determined target U-value) Breathable membrane 9mm osb sheathing 140mm timber studwork 140mm PIR insulation with studwork VCL 50mm x50mm battens (to provide service cavity) Plasterboard and Skim coat finish Queries: Is a 50mm cavity sufficiently wide? Will placing PIR insulation cold-side of the breathable membrane create a interstitial condensation risk? I have seen the VCL positioned internal side of the service cavity, however I believe the VCL is better positioned external side of the service cavity Any options or thought are appreciated

I'm working out a foundation design for similar cellar excavation, and its a struggle to get much detail online. Two tibbits perhaps of interest to you The SE design needs to perform under 2 conditions. First during the construction phase and then during the final condition post-construction. Obviously subject to soil types, structural bearings and the difference between external GFL and internal FFL (existing and proposed). The general rule of thumb allows general cellar excavate (In contrast to "hit and miss" 1 metre sq pits when undermining/underpinning) is to permit ground excavated above a 30deg angle away from the base of foundation, (I recall some sketch suggesting as deep as 45 deg).

My house has a cellar which I am considering converting to a habitable space. Currently headroom is only ~1.8m, to achieved sufficient headroom and compliant floor build-up I would need to excavate the floor sub-level to ~400mm below the base of exsisting footings. Typically that would mean underpinning the footings however I think there is an alternative method where a concrete ring beam is cast at the base of the footings. This onits the need for underpinning works albeit at the cost of floor space. Is anyone familiar with this method and if so can you point me in the direct of a technical resource outlining the method?

Hi Simon, Great that Design Guide sounds exactly like the kind of resource I'm looking for, that's evening reading sorted for the next few weeks! Thanks for the other points also. Did you solely design your system or did you both design and install it as well, and if so did you weld the manifolds up yourself? I guess the key is to pressure test what you install. I think the manifold system also facilitates this as you can isolate testing and potential leak points a little easier

Hi Tony thanks for the response. The house is 1870's semi, currently no wall insulation. I can't do EWI as it would cover my attractive brickwork and I'm against IWI on solid walls due to the risk of interstitial condensation As such I believe heat pump is may not have the sufficient high temp output for a building fabric with such relatively poor thermal efficiency. Gas fired CH seems to be the best option AFAIK. The plan is the located the plant room in the cellar, and I have some flexibilty which part of the cellar the plant room will be located in, so have scope for a centrally located vertical riser.

Thanks Jimbo, that's helpful. Keeping the runs <6m isn't so easy in even a moderately sized house, certainly points towards having the plantroom or (manifold at least) centrally located if possible. I've a cellar so that gives me a bit of flexibility on where to locate all that gear on the floor plan.

Anyone at all able to chip in with any kind of advice on my post above?

Just to add further description of the property: Semi detached Victorian Floor area ~216 m sq /2325 ft sq. Laid out on Cellar, Ground and First floor 4 ensuite bathrooms (no main bathroom) 1 cloakroom wc