Here's how I've done the board-on-board cladding on the gable ends of the house.
Traditionally (i.e., in recent architectural fashion) board-on-board cladding has been done with fairly durable softwood which is left untreated to weather to a nice grey colour. It's expensive though and doesn't always weather uniformly, particularly if there's any shading, so I'm a bit sceptical.
Instead, I decided to use the same sort of idea but with cheap treated softwood which would need painting for any sort of longevity and also for looks. For now I've just painted it with brown fence paint so that both the externally facing surfaces and those to the 50mm ventilated cavity on the inside are covered. Later I'll paint it with something a bit more suitable for the house's style: black for the outside boards and white for the boards in the porch/greenhouse.
The boards are 150x22 mm and 4200 mm long. I decided, rather arbitrarily, to overlap them by 30 mm so each pair of boards (back board and adjoining front one) effectively covers 240 mm.
I was dithering between putting the battens on 600 or 900 mm centres so decided to use 700 mm as that divides into 4200 mm nicely. Obviously the top and bottom battens don't go quite on the nominal centres but it's simpler to start with the nominal spacing then move those in a bit. More discussion of this when I talk about the east gable.
Here's the west-gable story in pictures. As usual, click for larger versions.
Openings in the walls need to be surrounded by firestop to slow down the spread of fire in either direction between inside the house and the outside surface. I'm using these 1.2m “sausages” of mineral wool in plastic wrapping which get stapled to the wall. Here, round the main entrance. The bit across the bottom will be filled in when the porch/greenhouse floor is added.
The colour in the plastic covering disappears pretty quickly on exposure to light so I covered them with DPC to protect them and also protect the corners of the openings a bit.
Similary, firestop up the side to slow down spread of flames from the gable cladding into the structure of the porch/greenhouse roof. There'll be separate firestop on the edge of the main roof for protection between it and the porch/greenhouse as a whole.
Similarly covered with DPC.
A virtual milestone for my van. A few weeks later it failed its MoT fairly spectacularly: a brake pipe burst during the test. Tester was a bit grumpy about that but got it fixed and through the test a few days later though I suspect it's on its last year.
Doing a small area to begin with, battening on the north side of the entrance.
Set up inside for painting the boards, which is pretty time consuming but at least can be done on days which are not suitable for working outside. Battens across the study to support boards being painted. Painted boards stacked on the floor of the shower room. Next “batch” of boards waiting to be painted stacked to surface dry on the north (left) side of the battens.
First set of “back” boards nailed up.
Then front boards nailed on top.
Firestop for roof of porch/greenhouse…
…and down the south side with DPC.
Area of gable blocked off for services to come through. Primarily the inlet and exhaust pipes for the heat-recovery ventilation but also the cables for the PV and other electrics.
Nails banged through in each of the five corners to show where to drill on the inside when the time comes.
Looking up inside to see one just sticking through the OSB for now.
Wider view with DPC covering.
Somewhat overexposed shot of many of the back boards in place. I had the camera in the wrong mode and took a while to notice.
Board with 150 mm spacing of boards marked together with the 30 mm overlaps clamped (“spreadered”) up against the bottom of the bottom boards to make nailing the top boards easier. From the scaffold tower I could hold the top of the boards and position the bottoms easily looking down, nail the tops of the boards then make my way down keeping them lined up nicely.
Extra batten below the south purlin to support the tops of the boards below that.
General view with all of the back boards and most of the front boards.
Perhaps a clearer view of another (slightly shorter) bottom-spacing board for the last front board below the south purlin.
Awkward shaped front board up the side of the north purlin.
Another awkard-width back board up the right hand (south) side of the entrance.
Done, except for a small bit of board right on the south side.
I've got some rolls of fibreglass mesh to close off the tops and bottoms of the ventilated cavities. I just haven't decided quite how I'm going to deal with the “lumps” of the board on board, yet.