Saturday 28 November 2015

raising our walls

The crew :)
Today was a massive day - we've raised our walls! Whoop whoop! We've finally made the step from 2D to 3D and the tiny house is starting to feel pretty real now! Check out this timelapse of (almost) the whole framing process, including insulating the subfloor with sheep wool.

Big thanks to our great helpers Selene, Tabea, Pippa and Jamie! Couldn't have done it without you :)

The first corner is up
Decision-making was a truely communal process. We managed to get all walls
more or less level and square with combined brain and muscle power.
Even a broken wrist didn't stop Selene from helping us!
Done for the day

frames and walls

We've spent the last week framing our walls and it's been a huge learning curve. The second-hand nail gun made things a lot easier than nailing frames together by hand. 

We used H2 MGP10, 90x35mm pine at
a 450mm stud spacing for almost all of
our frame parts
Our timber delivery arrived - and
got rained on straight away. 

We've bought a second-hand framing gun and it's the bomb!
Our first two frames still felt a little wobbly after adding the noggins. A builder at a little local hardware shop recommended the type 17 bugle batten screws. We've become a huge fan of them!! They improved the integrity of our frames significantly, so we went on by pinning the frames together with the nail gun and then adding some bugle screws. 

Skew-screwing a bugle screw
into a noggin

A type 17, self drilling bugle screw

We also used double sided stud ties on some of the studs to account for uplift forces that our tiny house might experience. After all, we are building our tiny house to (hopefully!) withstand high wind loads and earth-quake like conditions during moving.

Stud ties
Double-sided stud tie connecting
a stud to a bottom plate

A bushfire came a little too close for comfort 
Tabea is turning into a badass carpenter!
We divided the long sides into three seperate frames, for easier installation
We worked off the section cuts from our SketchUp model to build
each individual frame

Next, we will be putting the frames together and raising the walls!

Thursday 26 November 2015


The subfloor is finished and we thought we'd let you know how we went about it. 
We installed 120x35 H3 pine joists to support our floor and attached these with joist hangers directly to the trailer. We could have had steel joists welded in when we had the trailer made, but we wanted to reduce both costs as well as thermal bridges as far as we could, so opted for the timber joists for additional support.
Tabea installing a subfloor joist

We then attached 0.4mm galvanised sheets to support our insulation batts. Even though it was extremely awkward, we decided to install the sheets from underneath. This way we can access the subfloor from the outside, if we ever needed to for maintenance. The 0.4mm sheets were the thinnest we could get and while they do feel a bit wobbly, they are sturdy enough to do what we need them to. Working with the galvanised sheets was unpleasant and noisy and we're glad that we picked timber and not metal as our main building material!

Not very pleasant: 
Working with galvanised sheet 
metal in confined spaces

Very pleasant: 
Working with fluffy 
sheep wool insulation

We painted the plywood that we used for the subfloor with a borax solution before installing it. We read that this would deter termites, but hopefully they shouldn't find their way into our subfloor anyway, as everything below will be sealed and out of metal and H3 (external-grade) timber. We're also not sure how effective the borax solution would be long-term, but we had it sitting in the cupboard anyway and it's a natural product, so we thought we'd just do it. Luckily, the termites here are not as aggressive as up north, so we should be fine as long as we regularly check around and underneath the trailer. Fingers crossed.

Borax mixed with hot water
On the photos you might have noticed that our joists are not evenly spaced. This is because we needed extra support in spots where we'll be putting braces and and an internal wall. Other joists had to placed where the standard-sized plywood sheets for our subfloor would meet, so at just under 1.2m apart.

We left 2mm gaps between the plywood sheets to allow for expansion. In hindsight, we should have added those 2mm to the 1.2m joist spacing. 
We then sealed those expansion gaps with caulk, both to increase airtightness at a later stage and because we were worried about rain or bugs getting into the subfloor insulation during construction. Now that the subfloor is finished, we have a clean slate to build our tiny house on!

Cutting the plywood to size.

Sunday 15 November 2015

first day of building

We finally started our build yesterday. What a day! Temperatures reached 38°C (100° F) for the first time this summer and from about lunchtime the trailer was too hot to touch without gloves. A special thanks goes to our dear friend Tabea for giving us a hand!

Here is a time-lapse video of us fitting some 120x35 H3 subfloor joists with joist hangers and galvanised tek screws & type 17 timber screws:

By the end of the day we were a little worn out from both the excitement and heat but that didn't stop us having a little celebration to mark Day 1 once we got home. Things may have gotten slightly out of hand which led us to skipping today's plans. Instead we stocked up on more hardware and a big water jug to keep us hydrated.

Anyway, Tuesday we should be back at work receiving our timber delivery, which will give us plenty to do for the unforeseeable future!

Anz and Tabea are marking where to put the joists

Izzy getting ready for the very first cut!
Happy and exhausted after our first day on site!

Wednesday 11 November 2015

the trailer is here!

Our trailer arrived today! Hooray! It all went surprisingly smoothly and the trailer is so well balanced that we can still manoeuvre it by hand, if we put some weight on the back. We are really happy with the way the trailer turned out. Our trailer builder did an amazing job and everything from the welds to lights, breakaway device and wheels looks fantastic!
We'll clean up the site a bit more tomorrow, get it into the right spot, level it, and we will be ready to go. Exciting times ahead!

This is it!
An old rusty pole belonging to an obsolete clothesline
had to be moved to make way for the trailer. 
Almost in the right spot! We may have to prune back the tree a little
but we'll appreciate every inch of shade we can get over the next few months.

Monday 9 November 2015

getting excited

We had a call from our trailer manufacturer today and they will deliver our trailer later this week - things are getting serious!

Sunday 8 November 2015

making it up as we go

As we might have mentioned before, we didn't give ourselves a long planning head start before starting the build. This is forcing us to use the plan-as-we-go method a little more often than comfortable :)

We have been putting together our first timber order and getting quotes from local suppliers. This was hard because it required setting a lot of constructional details into stone and decision time is serious time. Also because some details affect other decisions and details, and so on. One example: 

Our initial wall build up from outside to inside was going to be this:
- Weatherboard (maybe western red cedar)
- Airgap with marine ply battens (the 'rain screen')
- House wrap (planning for Proctorwrap Enviroseal Commercial)
- Bracing plywood (AS1684.2 states that 7mm F11 provides enough strength)
- Timber frame with mineral wool insulation
- Tongue and Groove interior lining

Nice and easy. As seen on many Tiny House blogs. The only problem is building science. Once you start reading about vapour retarders and air barriers it becomes apparent that there could potentially be moisture problems in a small space with an inherently air-leaky surface such as T&G boards and with having the  most vapour impermeable surface, the plywood, on the outside of the building. Could there be a situation in winter, where moist air from the inside saturates our plywood by condensation (adsorption)? A dew point could possibly form on its surface when temperatures outside are a lot colder than inside. Are we overthinking this? Is Perth's climate forgiving enough not to have to worry about vapour retarders and airtightness? Will we even live in Perth with this house for the longest time, because Albany's climate, for example, could pose different challenges on the house?

First of all, reading up on this issue made us aware that air transported moisture is supposedly a much greater concern than diffusion through wall materials. The sheer volume of water penetrating into wall cavities in a normal house by air leaks compared to vapour diffusion is apparently massively larger. 

Secondly, reading up on websites like and, especially helpful, made us a little less nervous about the need for vapour "barriers" in this part of the world, but certainly increased the concern for airtightness of our walls. 

As soon as you start discussing airtightness of buildings, many people seem to argue that it must be unhealthy to live in a hermetically sealed space that "cannot breathe". Others, like those following ideas of the PassivHaus design, rave about airtightness to achieve energy savings. Personally, we like energy savings and natural, healthy spaces, and think that these don't have to be exclusive of each other. Airtightness in buildings is however such a huge topic that we can't do it any justice discussing it here in a little blog post, but what we arrived at for the moment is this: 

We like our walls to breathe in the sense that we like our walls to be able to dry out before they start to rot. Unintended air leaks however are not so great, as they not only increase energy needs for cooling and heating in a tiny house with little thermal mass, but also introduce moisture related problems. 

If you have a leaky house, as is the case with many older, traditional houses, moisture can easily move through the walls via cracks in walls and gaps around windows and doors, electricity plugs, light switches - you name it! The house we currently live in is so leaky that you can feel an actual draft in winter and it gets ridiculously cold, considering winters aren't even that harsh here in Perth. Then again, those old houses get crazy hot in summer! 
What we are after is definitely not a vapour barrier (think living in a plastic bag) but to allow for vapour permeability on the inside and outside of our wall. 
As most of the steam and moisture that could potentially enter the walls will be created on the inside of the building (cooking, showering, breathing,...), we want to achieve a fairly high level of airtightness on the inside of our walls, to stop this moisture getting into our walls in the first place.
We will try to relax and not worry too much about diffusion through wall materials and we'll just rely on the moisture-transporting properties of our timber and housewrap. 

How are we achieving this? Well, we really wish you could tell us! As we can't use the tried and tested drywall in our build as a vapour permeable air barrier, we are currently considering options like using a modern smart vapour retarder and airtight layer (Intello Plus or similar) on the inside behind our wall lining or just plain old thin plywood, which is fairly air tight (if meticulously installed!) and has smart vapour retarding properties as well. Another option we have seen would be to put the outside plywood sheathing onto the inside, which could address a lot of our concerns. However, we are both not really comfortable with relying on house wrap alone for protecting our walls from the elements, without having some sort of plywood behind it as a "back up" in case any rain does find its way behind the cladding and through a puncture or leaky seal in the housewrap. We will share our new wall layout later, once we are sure about it. Hopefully that will be soon, as we are expecting our trailer and first timber within the next week! AAH!

While we were considering all this, another idea came up and is really growing on us: Ditching a lot of the T&G lining boards and using wallpaper-covered plywood on some surfaces inside. We'll see.....

Another quick detail that we would like to share: In hindsight, it may have been more practical to order our trailer like this:
This detail shows the outermost steel beam and the subfloor and wall on top of it. The difference to our trailer is that the steel angle is welded onto the outside instead of the inside. The revised detail would allow for easy access to bolts, even after the whole floor has been insulated.

Unfortunately it's too late for us as our trailer is almost finished, but maybe someone else can learn from this :)

Let us know what you think about airtightness and vapour barriers/retarders in tiny homes - any experience or advice will be much appreciated!