Hi all,

I've been lurking and asking the odd question here for a while now, so first of all a big thank you to everyone who's helped us so far, especially @craig @Owain1602 , @Nickfromwales , @JohnnyB , @Nick Laslett and @zzPaulzz . The knowledge and generosity on this forum have been invaluable.

A bit of background on why we're doing this. Honestly, if it were just us, we'd be very happy staying in our little 4-bed semi for the rest of our lives. The only reason we're on this self-build journey is our disabled daughter. We want her to become as independent as possible while staying close by, so the house is designed around a self-contained annexe for her and her carer(S), attached to the main family home.

We're now at the point where we'd really welcome some fresh eyes on our plans (attached). We're building on a plot near Ipswich, with a total floor area of around 350m², including the annexe. Planning hasn't been submitted yet, so this is a good time to catch anything we've missed. Any comments, observations or "I wouldn't do it that way" are all very welcome.

Structure
We're leaning towards a timber frame with I-joist walls and roof cassettes. The main reason is natural insulation (wood fibre, cellulose or hemp), for its decrement delay and to help prevent summer overheating, which matters as much to us as winter heat loss. Speed of construction is a big plus too. We're targeting U-values of 0.13 for the walls and 0.11 for the roof and floor, with a brick outer leaf and some Millboard cladding, plus a standing seam roof (Catnic Urban) with a small flat roof section.

Foundations
Our preference is an insulated raft, but we haven't ruled out traditional trench fill with something like Marmox Thermoblock to minimise thermal bridging at the wall-floor junction. The site is sand and gravel/crag.

M&E

• Full MVHR for the house and annexe

• ASHP with underfloor heating on the ground floor; we're still deciding how best to heat and cool upstairs

• Solar PV with battery storage (AC coupled with safety the priority given the timber frame)

I'll start separate threads on specific topics (foundations, frame choice, cavity barriers and so on) and link them back here, so this thread can stay as an overview.

Thanks in advance,
Jeremy

PW1629-PL03revC Proposed Floor Plans and Elevs.pdf PW1629-PL02revC Proposed Site Plan.pdf

Edited 2 hours ago2 hr by Jeremyw
Forgot to tag someone!

Welcome.

Had a quick look and two things sprung to mind when looking at your plans:

1. Maybe worth considering a separate door into the accessible bathroom. Obviously not sure on the particular situation your daughter is in but just seems to me that navigating from the living room to the bathroom through multiple doors in a wheelchair is suboptimal and a more direct access from the living space might be a good idea.

2. I notice you appear to have the main staircase to your upstairs through your living area. I believe this triggers extra fire safety measures that can add a lot of cost and possibly ongoing maintenance (sprinklers/misting systems). Worth considering if that is worth it vs an alternate design that avoids the need.

48 minutes ago, -rick- said:

Welcome.

Had a quick look and two things sprung to mind when looking at your plans:

1. Maybe worth considering a separate door into the accessible bathroom. Obviously not sure on the particular situation your daughter is in but just seems to me that navigating from the living room to the bathroom through multiple doors in a wheelchair is suboptimal and a more direct access from the living space might be a good idea.

2. I notice you appear to have the main staircase to your upstairs through your living area. I believe this triggers extra fire safety measures that can add a lot of cost and possibly ongoing maintenance (sprinklers/misting systems). Worth considering if that is worth it vs an alternate design that avoids the need.

Thanks Rick, really appreciate you taking the time to look.

Great minds! We went through exactly that with the architect yesterday. A direct door from the living space into Jessica's bathroom is going into the next revision, so she won't have to go through multiple doors to get there.

Good shout to flag it. My understanding of Approved Document B is that sprinklers or misting, or a fully protected stair, only come into play when there's a floor more than 4.5m above ground, i.e. three storeys or more. For a two-storey house, an open stair rising from the living area is allowed as long as:

• every first-floor habitable room has a compliant escape window (min 0.33m² clear opening, 450mm min width and height, sill no higher than 1100mm)

So I think we're OK on that one, but I'll double-check and keep an eye on the escape windows to the bedrooms. Happy to be corrected if anyone's had a different experience!

3 minutes ago, Jeremyw said:

Thanks Rick, really appreciate you taking the time to look.

No problem. I find it good practice to work through other peoples designs as a way of helping guide my own thoughts on my future project (still a long way away).

3 minutes ago, Jeremyw said:

Great minds! We went through exactly that with the architect yesterday. A direct door from the living space into Jessica's bathroom is going into the next revision, so she won't have to go through multiple doors to get there.

Great!

3 minutes ago, Jeremyw said:

Good shout to flag it. My understanding of Approved Document B is that sprinklers or misting, or a fully protected stair, only come into play when there's a floor more than 4.5m above ground, i.e. three storeys or more. For a two-storey house, an open stair rising from the living area is allowed as long as:

• every first-floor habitable room has a compliant escape window (min 0.33m² clear opening, 450mm min width and height, sill no higher than 1100mm)

I believe the issue is introduced when you have a kitchen within that living area. If you could seal off the kitchen from the rest of the space I think it would be ok.

41 minutes ago, -rick- said:

No problem. I find it good practice to work through other peoples designs as a way of helping guide my own thoughts on my future project (still a long way away).

Great!

I believe the issue is introduced when you have a kitchen within that living area. If you could seal off the kitchen from the rest of the space I think it would be ok.

Thanks Rick. I think the kitchen separation comes from the three-storey open-plan option, where you need the kitchen enclosed plus sprinklers. For two storeys, ADB just asks for a heat alarm in the kitchen where it isn't separated from the stair, along with the escape windows upstairs. Our architect is obviously comfortable with the layout.

22 minutes ago, Jeremyw said:

Thanks Rick. I think the kitchen separation comes from the three-storey open-plan option, where you need the kitchen enclosed plus sprinklers. For two storeys, ADB just asks for a heat alarm in the kitchen where it isn't separated from the stair, along with the escape windows upstairs. Our architect is obviously comfortable with the layout.

Ok, I've gone back and double checked and I think you are probably right. It's been a while since I looked at the regs and this was a specific area that I was interested in for my own plans. So no kitchen in same room as stairs (even with upstairs escape windows) was fairly firmly etched in my memory. Not sure where I've gone wrong in the past and I'm still half thinking there's a reason it's so firmly in my mind. Curious.