Canberra custom KDR

So, now that we're (finally) underway with our KDR in an established Canberra suburb, I should probably get around to documenting our build, if only for our own reference.

It hasn’t been a smooth journey (including a builder bankruptcy, errors in the law, negotiations with neighbours, bank issues), but we’re here now. I'm intending to fill in more of the backstory as I go along, to hopefully serve as learning points for others.

Anyway, the design:






There's also a separate large garage to the north, connected to the house via a covered breezeway.

The design is my own (the culmination of nearly 18 months of iterative design and a LOT of learning), designed to meet a combination of our own requirements and the specific site features. It’s intended as a forever home, designed for flexibility, including the option of being adapted to multi-generational living in the future.

The two-storey design was chosen to maximise garden space and to take advantage of the views - the house is at the top of a ridgeline, with good views in almost all directions (but especially North and West/Southwest) once you get above ground level. Externally it's designed to reduce the visual impact of the two-storey design by blending in with the surrounding suburb and the reserve it backs onto, and references the traditional Australian country farmhouses that can still be seen around the region.

Although we’re (comparatively!) young and all in good shape at the moment, as a forever home we wanted to allow for ageing in place (and contingency options should something unfortunate happen in the meantime). The design generally meets at least the Silver standard of the accessibility housing guidelines as-is, and is also designed to be readily upgradeable to the Platinum standard in the future (if required, fingers crossed!).

It’s a passive solar design - natural light, comfort and energy efficiency are all very important to us – with insulated foam cladding and double-glazed UPVC windows. We're definitely not chasing the Passivehaus standard, but we have paid attention to a reasonable level of airtightness. The design and orientation meant that despite being a larger house (larger than we were aiming for - part of the backstory to come) and some of the compromises in the design (more on those later), it still achieved a basic NATHERS rating of 7.4 stars with no effort; the final design incorporates higher-rated windows, upgraded wall and roof insulation, and added slab insulation, compared to what was used for the rating, so the actual ‘as built’ rating will be much higher. IF we can be bothered, we’ll get it re-rated, but we’ve got what we need to build, so aren’t bothering with it now (and NATHERS isn't necessarily that good as a rating system anyway once you get to this level).

As of writing: the site scrape happened last Friday, plumbing (drainage) went in on Monday, and currently the slab forrmwork is being assembled for inspection (both the builder's certifier and our independent inspector) tomorrow (Thursday) afternoon, with the slab pour scheduled for Friday morning. There's rain (and possible thunderstorms) forecast, though, so we'll see how we go...

Well, the slab pour didn't happen today (as expected) - it's been rescheduled for next Thursday (with pre-pour inspection moved to the day before) - but looking at the week ahead forecast, there might be rain then, too. We'll see how we go.

At this stage further delays to the slab pour aren't the biggest issue we face - it was only last Wednesday we got the phone call telling us that our selected frame manufacturer had closed their doors (Statewide Frames and Trusses). Our builder has been particularly hard hit by the sudden and unexpected closure - it's hit his entire schedule, and he's certainly a bit stressed at the moment. The hardest part is finding suitable quality carpenters who can start before next year - our original schedule had the frames completed and roof on (after wrapping) before Christmas, but that's not going to happen anymore. Just when we were thinking that there wouldn't be any more issues - oh, well, all part of the experience.

Following, very interested in your passive solar design. We put a lot of thought into that for our design too, but unfortunately still had issues with NATHERS due to the shape of the house.

Congratulations on the beginning - it can be a long road to get there!
Plans look great, and very sorry to hear about the frame supplier. Stressed builders are not fun.
Hope it gets sorted quickly and am looking forward to following your progress.

Very interested to hear of your build and watch as it progresses. Congratulations on the first parts of the build happening! Must be exciting after so much planning.

We too have been designing our “forever home” for about 12 months, similar to you, lots of learning and changing! Have read the yourhome gov site many times over!!

Can you tell me what insulated foam cladding you are using? And did you actually do those drawings or have a draftie do them ?

All the best with the build, hope the framing issue is resolved without too much fuss...

Yes, I remember your design! NATHERS was always going to be an issue with your shape - it just makes the passive solar aspect all that more important to compensate (which I think you a aware of and were on track for). There are many limitations to NATHERS anyway, as we're well aware - it's a good "first cast", but if a house is well-designed it's energy usage and comfort can be well above what NATHERS indicates (which is our aim for this one too).

I did briefly consider a courtyard design, primarily for aesthetics (I've seen some really nice courtyards around here!), but decided against it for (amongst other reasons) the significantly increased ratio of external walls to interior volume (and hence reduced energy efficiency).

In the end, we achieved a "best of both worlds" approach by keeping the house itself as a simple closed structure, while separating the garage (which had the additional benefit of reducing the area needed for the driveway and leaving more space for garden). We've ended up with an "external courtyard" between the house, garage and breezeway (the lounge room - marked as "Media" on the plans - is the room that looks into this courtyard to the north). Most of the effect and none of the energy disadvantage - we we lucky that we were able to do this within the site.

Thanks!

The poor builder has basically had his whole business put on hold for a couple of months - he now can't progress his pre-framing builds until he can get replacements going, and due to the insurance limitations on the number of builds you can have going at once, that means he also has to hold off on signing up new clients until things get going again! He's also takes pride in his efficient scheduling, so having a whammy like this hits hard on his professional pride, too. We're a little disappointed that this has happened, but can easily cope - he's the one with all the stress, not us!

The company was Statewide Frames and Trusses - their sudden closure has affected a lot of builds and trades not just in Canberra, but in the surrounding regions as well. Our builder is putting in a lot of time and effort to sort out replacement frames and trades, and we're confident that we can get moving again soon.

Our builder is quite transparent on pricing, and he actually gave us the choice of three quotes from three different framing companies - we agreed with him that Statewide were the best quote, but if only we had a crystal ball! (of course, maybe the reason why they were the best quote is also the reason for their closure....).

Yes, yourhome.gov is a great resource!

We're using Dulux Exsulite as our cladding, which is an EPS foam product similar to many others on the market. With EPS cladding, the products themselves are all materially identical - what makes the difference is the installation systems. Exsulite has a good range of technical documentation and trade support behind it, and also (unlike many others) has a cavity system, which can be combined with a good building wrap to provide excellent moisture management and condensation protection.

There's been a few cases in the past year of EPS installations that haven't been done correctly and have allowed moisture to penetrate into the frame and/or the rest of the building. Naturally, that led to some articles saying "foam cladding is awful, don't use it" - funnily enough, if I were to build a brick wall without using mortar, nobody would be blaming the BRICKS for the resultant leaking Having a cavity system provides a solid second line of defence even if there's an issue with the outer waterproofing.

The drawings I posted were done by our builder's drafting company, but off plans that I'd originally done (they took my plans and and turned them into proper construction documents). It actually took a few goes back-and-forth to get them to copy EXACTLY what I had on the plans and not add their own "interpretations".

I did my original planning in Home Designer (by Chief Architect), and then managed to get my hands on a copy of Revit (Revit and Archicad are the two main pieces of software used by professional drafters in Australia), and had properly scaled, laid out, dimensioned etc. plans. It's possible that I could've gotten them up to construction standard myself, and I even considered doing a drafting course, but the time investment was too much for me (and most builders we spoke to were also - understandably! - wary about having contract and construction plans done by anyone other than a professional draftie - so we probably would've ended up paying for it anyway).

This was the situation on the weekend, just waiting for the concrete:




It looks much larger in the photo compared to real life!

The preparation looks pretty good to my (inexpert) eye. The reo is supported on chairs and evenly laid, overlapped as per the engineering drawings and neatly tied together at the overlaps. The corner reinforcement is in place and the pods themselves are largely true (a couple will need a slight straightening prior to pouring, which is not surprising).

Between the fairly level site and the smaller footprint enabled by going double-storey, the cut and fill was only about 15cm each way (the photo above was taken from the cut corner across to the fill corner). Like most of Canberra, soil class is M. No rocks were expected or encountered, and no piers were required. Upon completion, a 1m continuous concrete path around the entire house will help with slab protection (as well as termite defence, maintenance access, stormwater management, and just being a generally useful path).

The slab edge insulation is also in place, although it's been cut a little roughly in places and will need further finishing on the top edge to be able to butt it flush to the cladding. Here's how it looked last Wednesday while it was being laid:



Learning point: thoroughly discuss and document (with diagrams) a slab insulation scheme (edges, base, joins) and how it interfaces with wall cladding and termite protection as part of the contract drawings. It's a lot more involved (and with more options and uncertainties) than you might think, and if you just say 'slab insulation' then you could end up with all kinds of outcomes, some much more useful than others....

In our case we knew about it early on but kept forgetting to bring it up at relevant times, and the details didn't make it into the contract documentation, leaving a lot of ambiguity. It worked out okay in the end, but there was a lot of unnecessary stress sorting it out in time (and a few hundred dollars for an engineering revision).

Due to the weather forecast, the slab pour on Thursday was cancelled in advance. Which was a pity, because as it turns out the rain held off for the whole morning, and when it did come in later in the day it would've been well-timed to help curing. Oh, well, you don't know these things in advance! Pour has been rescheduled to Monday.

The independent inspection went well with no major issues found, just identifying a couple of minor things to be finished off just before the pour.

Alternative framing supplies and trades have now been sourced, with one exception. I'd specified floor trusses for the upper floor (Posistruts) - but the truss manufacturers seem to be all booked out until next year. The builder is waiting to hear back from one more (based a couple of hundred ks away) - but unless they come through, we'll need to make the call: I-joists (hyJOIST) with a framing start in mid-late November, or hold out for trusses but delay framing start until at least late Jan.

I went with floor trusses over I-joists due to perceived vibration reduction advantages, although it's hard to find publicly-available solid scientific/engineering data on this. It's investigation time again... will I-joists be an acceptable alternative?

As background, the floor structure overall needs to be very solid and firm, because I'm unusually sensitive to floor bounce and vibration (and I mean really sensitive - I can even pick it in up in some heavily engineered structures such as shopping centres and multi-storey carparks). I went with floor trusses over I-joists due to claimed/perceived vibration reduction advantages.

I also specified the upper floor to live loading of 2.0kPa (above the 1.5kPa Australian single-building residential standard and in line with the Australian standards for multi-residential dwellings and hotel bedrooms). The Australian standards do seem a bit light-on for floor loading by comparison with other countries (e.g. in the US its 40psf live loading for residential living room floors, which is roughly equivalent to 2.0kpa - the US allows 30psf/~1.5kPa only for bedrooms and attics).

The upper flooring itself will be Hebel Powerfloor - multiple reasons, including insulation, acoustics, thermal mass, solid feel, no squeaking, and reduced vibration.

Hopefully either the last truss manufacturer will come through, or I can be satisfied that I-joists are an acceptable alternative (either on their own or in combination with the above factors). Otherwise I have a difficult call to make....

Sorry to hear that the slab pour was delayed - hope everything is all good for next week.
I think for me the aggravation factor'' would be the decider with the flooring. If the vibration will annoy you every day for as long as you live in the house, I'd wait for the right materials.

Pour complete!


Note the very expensive and high-tech wet-curing system that is very definitely not jury-rigged from various miscellaneous garden watering components

A warm sunny day with lots of wind was not ideal for a slab pour, especially when using N25 concrete (stronger than the standard N20), so we had to make sure that the slabs were properly wetted to prevent surface crazing (quite apart from the extra strength you get from wet-curing).

Unfortunately, some of the slab-edge insulation was dislodged when the formwork was removed, but it should be readily fixed back in place once the slab has cured.

And in the other big news of the day, the builder has managed to find replacement sources and trades for the frames and trusses, including the Posistrut floor trusses we wanted! Framing should now commence in three weeks' time (which conveniently works out to be a good length of time for the slabs to cure).

That's a great looking slab - well done. Did you get some rain overnight as well?
Good to hear that you can still get the framework you want as well.

About 5mm - another little bit of help for the curing!

The slab ended up turning out quite well - good enough for a polished concrete finish, despite not being spec'd as such (we're going with tiles, mostly for aesthetic reasons).



Not that you can see in the photo, of course, but there's only three small hairline surface cracks in the entire slab. Not bad, especially for N25 concrete! (the slab looks a bit 'blotchy' in the photo due to residual damp spots from recent rain that hadn't fully dried out when the photo was taken).

In the bottom-left of the photo you can also see part of the hand-dug basic trenching system used to drain water away from a couple of spots near the slab that were subject to run-off pooling due to the fall of the land (one of those spots is visible in the bottom right of the photo). This was especially important during the wet-curing process, and given the weather forecast for the rest of the week will probably be just as important going forward!

The green 'fabric' around the edge of the slab is the termite protection - Termigreen, which was selected primarily because it's a physical barrier which doesn't form a thermal bridge through the insulation (unlike metal solutions, e.g. Termimesh - another advantage of not using a metal barrier is not having to worry about rusting). Termigreen is actually a combination defence (physical and chemical), with the pesticide being impregnated into the fabric; this means that (unlike many chemical barriers) it won't leach into the surrounding environment and doesn't require regular top-up treatments.

Thanks to the efforts of the builder, the schedule is now going full steam ahead, and we're aiming to have the framing completed and wrapped and the roof on before Christmas. It's by no means certain that this will be achieved - but it's now at least plausible, whereas a couple of weeks ago the odds of getting the roof on before the break were looking like zero.

Unfortunately, it's already looking like there's going to be more unscheduled delays - the carpenters are due on site tomorrow lunchtime to commence the framing work, but the weather forecast for the next three days is for a lot of rain and possible thunderstorms. We'll see how it goes...

In other site news, the resident apricot tree looks like it's preparing for a bumper crop this year!

As expected due to the rain, Thursday was a washout, as was Friday.

Then, today, this happened:






Ground floor frames are up! (Mostly, still a bit of finishing off to do).

They seem pretty good to our inexpert eyes - generally square and flush, noggins throughout, no timber that we could see with big holes or other visible defects. Without measuring anything, the floor plan looks pretty right on first glance.

It was an interesting experience walking around what feels like the first truly tangible signs of the house to be - the physical embodiment of the plans I'd spent so long working on and agonising over. For the first time I could see in full scale how the house works and how it interacts with the surroundings. I could check views from (future) windows, internal sight lines, distances and clearances, movement and flow in real life - fortunately, it's all working out well so far! (Not that that kept me from keeping on double-guessing the plan - should I have changed the window heights again? Should that display niche be deeper? etc. But on reflection and after the initial experience, I still think we've made the right calls).

Looking good.
It is a great feeling when you can see the house in the 'flesh' as it were.
Keeping my fingers crossed for your roof prior to Christmas.

As of yesterday - my precious Posistruts




Locked together with strongbacks, these should form a very solid base for the upper floor, much sturdier than typical Australian construction.




Here's an overview of the site, showing the garage in front of the house (the garage looks a lot larger in proportion due to the camera angle and foreshortening, it's not really that big!):




Mind you, there was a slight slip-up with the garage. We'd factored in the trees on our site, but it hadn't clicked that one of the neighbour's trees was overhanging the fence:



A bit of trimming will be required!

So, on Saturday the Hebel PowerFloor went on:





And then yesterday the upper frames went up:




The roof trusses have been craned up, but won't be installed until after the Proctorwrap (it gets wrapped over the top plate and then the trusses get placed on top.

We then had an official framing stage inspection today with the builder - a couple of minor things to do (which he was already aware of), but nothing major - the framing stage is essentially complete (and invoice issued).

It was a very wet afternoon, but fortunately we were able to see the views from upstairs before the rain set in - and it's as good as we hoped for! Getting up on ladders, flying camera drones, and estimating from what you could see on the ground is one thing - being able to finally see it directly in person is very different (and very reassuring, in our case). The existing trees provide privacy from our neighbours' yard (which was a concern for both us and them), and we've got excellent views all-round otherwise.

Looking good!
What function does the proctorwrap serve?

Being able to see the view instead of imagining it is a great feeling, and I'm glad that yours has met expectations. Hope the current rain doesn't slow things down for you too much.