SBMS

Not sure it’d work if you cut it in half and then cut back insulation you’ll have less than 50mm on each piece? What’s your cavity size? I think once piece is designed for up to 100mm, not to be cut in half to do 2x 50mm

Thanks @craigbut i think the drainage channel has a built in dpc that sits under the threshold (the bit that is shown on right of their drawing above). I don’t know if I’m overthinking it but wouldn’t the track be butt up against the top part of the R47?

@MJNewton can I ask how far set back your doors are from the front brick face? I am worried that the drainage holes for ours would sit on the brickwork, rather than ‘overhang’ and drain into a threshold drain if you know what I mean? How did you get around this, as I believe the track should be set back from the front face of the brick a little?

Following on from some really useful advice from @Dan F, @MJNewton and @craig I am wanting to use the Aquabocci R47 flush threshold on our sliding doors. I am struggling a bit with the detailing with our Raynaer's CP130s.. Basically, this is the profile for the R47: There is 26mm from top of the threshold to the side entry point. This is my track profile for my Raynaers CP130s: The Raynaer's low profile track has a front drainage system that I've indicated on the attached profile, but from the top of the track profile to the bottom of the drainage holes is about 22.5mm. If the top of the R47 was level with the top red line (top of the track), then the front drainage holes would sit higher than the side entry for the R47. Am I missing something really obvious, or is this flush threshold not compatible with my track? Thanks in advance

You’ll want a site surveyor who will come and survey the site (usually using a GPS gizmo to be accurate to within few cm) and then they’ll set out using stakes for the corners for your groundworker. Our groundworker then sprayed his dig channels on the ground between setting out engineers posts to get the corners. Often with planning there will have been a site surveyor at the beginning who would have surveyed and generated a site layout plan for the planning application?

Completely agree. They also haven’t got a clue how much it costs to build so don’t ask them. They were nearly 100% off our actual build cost with their estimate.

My experience of a couple of architects: they won’t design something that is cost effective to build and there will often be points on the build where the contractor scratches their head because the drawings don’t make sense. Case in point: architect designed our open eaves and didn’t think about clearance for windows on top floor. They hit the eaves (timbers now being cut down). Structural engineers will design things that are hugely over engineered to cover themselves, and aren’t specialists in things like trussed roofs so will design things using traditional steels and loose rafters rather than an engineered product. Case in point: our SE designed loose lay rafters with a chamber floor and about 12 steels for our attic room. They said attic trusses wouldn’t work. Builder got a truss roof manufacturer to design attic trusses - it passed engineers calcs and saved 11 steels and £7k in our pockets. If I knew now what I know I would try and ensure the architect and SE were designing a house that was economical as possible to build. We were so excited to design the floor plan and we didn’t know to pause and make sure the thing was as economical to build as possible. My view would be try and minimise on site labour for things like roofs, minimise steels, and maybe liaise with your builder at the design stage to point out any complex or expensive bits in the build that could be designed out.

As a domestic client, the health and safety responsibilities pass to the contractor (or principal contractor). https://www.hse.gov.uk/construction/areyou/client.htm

Fair enough @ETC. I didn’t advise the OP not to use a contract (I have a simple set of terms and conditions with ours) but was trying to impress the importance of prioritising and developing trust and finding a good builder over relying on a set of contracts. Especially if your contractor is more a one more band as appears the case of the OP. I always question the usefulness of a contract in the event of dispute - and having worked developing commercial contract agreements for a couple of decades can speak to the fragility of any contract when a dispute does arise, and the expense of enforcement, litigation, justifying limitation of liability levels, proving damages etc. On a self build scale, understanding the terms and conditions of a third party contract - even with a helpful QS - I’d still question.

Have you discussed with a solicitor what the cost of an indemnity to protect against this limitation for any future potential buyer would cost? They could get a quote to alleviate your concerns that it could be covered and wouldn’t be extortionate…

I’m not sure if I completely understand your detailing but thought I would add that I asked my BCO (and combined warranty auditor) about this today, as we are building a level threshold for our patio and 8m of sliding doors on rear of our build. His response was that the 150mm below DPC was not relevant for a door aperture and that an acceptable detailing of a slot drain abutting the doors would be written up in his report as satisfactory. He did however say that it wasn’t his call as to whether the warranty provider imposed a restriction on the policy - though he’s not aware of ours doing so as it is a common detailing. He said with his building regs hat on he was more than happy signing this detailing off. I asked what would we do if there was a limitation imposed with a future house sale and he said it’d be relatively cheap to get an indemnity to cover this as it is now such a common detailing.

If it makes you feel more comfortable I don’t think it’s bad advice, im just not sure how useful they are in the event of a dispute. Especially a third party contract where both parties fundamentally weren’t involve in its terms and authoring and at the end of the day need to consult a solicitor to interpret. If you’re a major construction project (see the ‘who uses us’ section of NEC) NEC model contracts are a great starting point but are they suitable for the lay self builder and lay contractor (that’s not rhetorical, I genuinely don’t know!)

My personal view is get clarity on the spec of what your builder will be doing, and develop a payment plan where you pay in arrears at the end of a stage. You might have to put a deposit down up front to get them going, but most of the materials they purchase and their costs will be on 30 day terms. I believe you should be looking at finding someone you trust to a high degree, and a contract is less necessary. If your builder breached it, would you really sue them? If they are a limited company they’ll have indemnity insurance that will pay defence costs anyway - could you afford to? If they’re not limited then how successful would you be and how could you prove a breach for example? Im not sure a contract is all that useful. Having really well understood responsibilities and payment terms - perhaps linked to BCO sign off is the way we went, and it’s paid off. If I was wanting to tie my build up into contracts I’d probably start wondering about how much trust I’ve built with my builder. Building is such a stressful, complex thing that in the event of a dispute you need to know you can talk and resolve amicably. Just my opinion!

I’m afraid you are miles out really. There was a thread a while back which was ballpark costs for a 300m2 build which I shared a lot of breakdown of our costs on: We are just getting watertight and are roughly coming in on the original budget - so our original was £1650 per sqm which is managed by a primary contractor so we are doing really well! We secured all prices beginning of year and it’d probably be nearer 2k per sqm now. Which is still reasonable. And ours is a square chocolate box brick and block, so relatively easy to build (be your aspirational pic which has more complex detailing I think)

Hi @ProDave yes - it was on the diagram as the Red line (150mm between rafters), then green line is 35mm over the rafters. Our rafters are 175mm so we have a 25mm air gap/felt sag, but we are using a breathable membrane (and have MVHR) so building control are happy with that setup.

Thanks @ProDave. Unfortunately roof is battened and tiling has begun so can't switch to warm roof. We were incredibly tight with ridge height due to planning requirements so would have been a push anyway. Do you have a view on the internal insulation of the room (yellow and pink bits on my dreadful diagram) for the MVHR?

Would you put rockwall in the dwarf walls (sound insulation) again? I might be missing the point here, so if we did insulate the floor and dwarf walls, would the eaves space not end up cold? Trying to work out what the actual difference between cold and unheated is... I guess eventually the heat from floor below and the attic room would end up migrating into the eaves space anyway?

Hi On our build the top floor has attic trusses and is a fully habitable room. The MVHR ducting runs within this eaves space. There are two options from the MVHR supplier for the ducting in the eaves - make the eaves a 'warm space' (lagging just the intake and exhaust with a 50mm isosleeve), or keep the eaves cold (lagging all the supply and extract that are in the eaves): Our current plan is to insulate between the rafters with 150mm PIR, with a 35mm cross batten of PIR. We were then going to insulate just the 'room' on the top floor with insulated plasterboard, and leave the eaves cold, but are now wondering whether we should not put the insulated plasterboard on and allow the eaves to be heated from the room? I've included a colour coded view of our options - the red and green bits (rafter insulation) is fixed: So we have 3 options (plus a fourth option where we don't make the eaves warm): 1. Insulate the room on top floor with insulated plasterboard, but leave the floor space of the eaves uninsulated, so heat rising from floor below keeps it warm 2. Don't insulate the room on top floor with insulated plasterboard, but insulate the floor space of the eaves so heat from the top room keeps it warm 3. Don't insulate the room on top floor with insulated plasterboard OR the floor space of the eaves, so heat from the floor below and the top room keeps it warm 4. Insulate the room on top floor with insulated plasterboard and the floor space of the eaves, and lag the MVHR ducting with ISO sleeve (i.e. make the eaves cold) We've pretty much been left to it ourselves (MVHR company won't make the call, SAP guys won't either). Our roof UValue for SAP Calcs is provided by the 150mm PIR + 35mm cross batten so it's more a design choice for ourselves.. Any thoughts? MVHR Plan (all ducting is in the eaves space):

Thanks @MJNewton for this, that's great.

Thanks Craig 👍

Thanks Craig - this has been incredibly useful. I was just going to say that it seems the aquabocci system referenced earlier looks like it would work. But is also crazy expensive! Have you a link to the metal one you've posted? I've struggled to find anything that permits side entry from the door and drainage from the pavers.

Yep, am getting that now! Tbh, we're sorted inside. as that's just about internal floor levels. It's the external bit we've struggled with. So if we put a slot drain in front of the track, I assume that the top of the slot needs to be lower than the top of the track profile, for the water to be able to leave? I'm not sure how the drain could be totally flush with the top of the track (my pink dotted line on diagram below), unless the drain took water from the side, rather than the top? (crude drawing below):

So just to be 100% - no cill required at all? Track directly onto outer blockwork with an acro channel/slot drain/aquabocci directly in front of it?Just got a bit confused as you mentioned Raynaers do a flush cill (which I can't, now, see the point of)

OK, least I'm not going mad. Is a different type of cill required, or do you put something like the Aquabocci directly in front to take the water from the track? (or both?)

Is it just me then, or is the cill pointless? Or is it just catching the water flowing out of the track at the front and directing it away?