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Board on board cladding - fixing advice / critique


markocosic
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I'm trying to choose how to fix our cladding on 'the practice cabin' and would appreciate some advice / critique / war stories please. ?

 

 

Specifically:

 

- Which screws should I use? (wide head or narrow head)

- How wide can I space them? (70 mm or 90 mm)

- It is insane to use regular (gold) screws if we're painting over the top with arcylic wood paint?

 

- Can you improve on the general detail? (other than not doing this!)

 

 

I like this: (painted board on board facade with "rukki roof" standing seam steel)

 

lato-119-julk.thumb.jpg.a450f4bb86f6c2828a8ec41632943d37.jpg

 

 

She likes this: (weathered board on board facade AND roof - rukki roof is perceived as too common out here

 

image.thumb.jpg.762d9ccf31fbbbb196714ed78799ac46.jpg

 

 

So in the spirit of happy wife happy life we're going to do painted board on board for both walls AND roof:

 

c4b373dc6349c28ced89a838a8b5eefd.jpeg.58623ebe4f85017c4ab0832fcb6faa25.jpeg

 

 

I'm fully aware that this is a daft roof covering but at this point I'm committed to giving it a go with the promise that the cuteness / timelessness of it will be worth it.

 

 

Labour: 

 

Me. Can lift >10kg. Can cut straight. Will climb roofs. Has no sense of style but likes to build things rather than bodging them where practical.

Her. Can lift <10 kg. Can paint straight. Won't climb roofs. Knows what enduring styles vs instagram fads are but has no sense of built vs bodged.

 

Tools are basic DIY. LIDL chopsaw, pair of makita circ saws, einhell cordless drill driver / impact, plus a monster trend router and worktop jig that we were given.

 

Neither of us are joiners and we like nothing more than dismantling everything we've just put together because we forgot a layer / fitted something backwards / changed our minds etc. Anything "you get one shot then you're wrecking it back out" is a risk. (pouring concrete, laying tiles, plastering walls, etc)

 

So much as I'd like an excuse for a compressor and a nailgun etc I don't think we want to nail or glue anything unless given a very good argument for it.

 

 

Areas to cover:

 

The design is a scaled up version of the grey cabin shown above.

 

Each "plane" of the roof is 4.6 diagonal x 16 metres

Each "side wall" height is 3.5 x 12.5 metres

The north gable end is 7 x 7 metres 

 

The south gable end (underneath a 3.5 metre roof extension much like the silver cabin) will be decking boards. We're leaving this and the deck until the sawmill has decking boards again. (everything is heading west at the moment)

 

Studs and rafters are 600 centres. There's 50 mm of mineral wool on the outside, then 25x100 furring strips to hold it in place, then a membrane (to give time to clad things / catch any rain that does come through), then 25x50 mm strings just to hold the membrane in place.

 

Roof pitch is 9:12 so readily walkable once you have horizontal battens. Currently there aren't any horizontal battens.

 

 

Cladding material:

 

The boards are ROUGH sawn and nominally 150x25 mm. 6 months ago €5/m2 would have got clean boards with  8 corners and 4 good edges. In the current climate...you get what you get and you're grateful. 

 

On paper it's a mix of pine / spruce. Looking at it I'd say mostly pine and I'd guess it's from logs trees no more than 300 mm diameter. (so some of the grain runs in interesting directions) Lengths ordered were 3.7m and 4.9m. Lengths supplied are anywhere from 4m to 6.5m and working out which is which is an exercise for the reader. (An "I can give you a delivery date for miscellaneous wood that's probably long enough; but it you want it graded and trimmed you're paying double or waiting until winter" type situation.)

 

Finished sizes are in the 140-150 x 20-25 mm range depending on how dry the board is now vs when it was sawn. Some are bone dry and almost look like planed wood. Others are possibly twice the weight and look like they were chainsawn into planks.

 

PXL_20210625_093940830.thumb.jpg.4f0d6d926ed33ce9c8129f6e85bd43b3.jpg

 

IMG-20210622-WA0004.thumb.jpeg.0ef6f7f2a099db415b92fe05683ba56d.jpeg

 

 

I'm busy grading / rough trimming / stacking these at the moment.

 

We have "good" boards with 4 edges along their length; no holes/bad knots; no major twist or bend or cupping. These are going to be the "outboard" boards.

 

We have "ok" boards with 4 corners at the bottom end and 2 edges; no holes/bad knots in the centre; some twist or bend or cupping allowed. These are going to be the "inboard" boards. (2 good edges upwards and 4 good corners downwards so that from the ground you see good ends and the bad edges are turned inwards/bad ends hide inside the eaves/ridge)

 

We have "good but short" boards that are going to go above/below doors and windows, and be gut down into "fillers" for the eaves

 

And we have "bad" boards. Some are straight but have holes in them. Some have splits in them. Some have twist/cupping in them. My plan was to rip these into the "25x75 mm" horizontal battens that will support the cladding.

 

This photo gives an idea of how bad the upper ends of the "ok" boards are.

 

IMG-20210622-WA0000.thumb.jpeg.578e40f904612d14ed0e9d1a151cf4b2.jpeg

 

We're expecting to have lots to choose from (the order was for 150% of nominal requirement ignoring the door/window holes) and cut many of the "poor" roof boards into "better" wall boards or even  "great" battens. I've added some extra spacers in that stack and ratchet strapped it tight whilst it dries some more. Perhaps they'll decide they like their new shape. For fixing purposes let's assume that I'm trying to tame these boards though!

 

 

Layup / Weatherproofing

 

The house is broadly weathertight / airtight as-is. The membrane is NOT a UV proof type but as long as we hide it from the sun I'm not overly concerned about water making it through the cladding. 

 

The house is on ground screws so you've got ~500 mm fresh air under the whole thing. There's an accidental "25 x 500 mm" cavity between membrane and the mineral wool thanks to how the insulation was fitted. (less at roof level where it droops to guide rain away from the battens) Then there's a 25 x 550 mm fully drained cavity formed by those retaining battens on top of the membrane. (more at roof level where the membrane droops)

 

I propose using "25 x 75 mm" horizontal battens spaced every 450 or 600 mm. This increases the effective cavity to 50 x 550 mm except where those battens are. I don't propose cutting an angle on top of them. These will be dead straight and aligned so that fasteners above the tops of windows/doors can match fasteners on the rest of the wall.

 

I propose assuming a nominal 140 mm board width and 30 mm overlaps. This will add lots of 80 x 25 mm vertical cavities outboard of the horizontal battens.

 

I propose cutting 8 mm wide and 8 (?) mm deep weathergrooves within these overlaps to "improve drying of the overlapping area" and form a capillary break / internal gutter especially for the roof. This is what I mean by weathergrooves:

 

bb15er.thumb.jpeg.44b985fbe19ded4854c3a18e0f05b240.jpeg

 

 

Router-ing 5 km of that would be epic but it isn't *too* laborious (cuts at walking pace) using this wide kerf blade of doom on the circular saw:

 

PXL_20210617_182025579.thumb.jpg.3015a59bd4c23446ae9c7ff0cdabd2e1.jpg

 

 

The eaves and verges will be sealed by sticking short "filler pieces" in like in that black example with the white windows. The route for breathing is base of wall (500 mm off the ground), vertical channels to the eaves/soffits (which form a box section linking the tops of the wall channels / bottoms of the roof channes), then sloping channels up to the ridgeline.

 

The ridgeline will be the limiting factor. This is to have a /\ shaped metal ridge capping leaving 80x25 mm gaps along its entire length. I'd guess 360 x 25 mm per metre either side of the ridge. 1 mm insect mesh there. 1 mm insect mesh at ground level.

 

 

 

These are getting painted with a "15 year" acrylic. (more flexible than alkyd albeit not as sticky / longer lived than sludge paint albeit not as easily refinished)

 

https://www.senukai.lt/p/gruntas-medienai-pentacolor-wood-primer-balta-10-l/4ke7

https://www.senukai.lt/p/emulsiniai-dazai-pentacolor-villa-novus-antracitas-10-l/5ulv

 

Rough sawn + quick 80-grit to remove splinters + quick brush to remove dust then primer (white) to crate a good base. Then one topcoat (anthracite) before fitting and probably a second topcoat (black) before fitting. Then the final coat in-situ and on top of all the fixings. (maybe important later)

 

Black is the wrong colour. We know. It'll probably be +70C in summer and -20C in winter seasonal swing. Or +70C during the day and 20C at night daily swing in summer. Red or grey would be more sensible (maybe as low as 50C in summer?) but this cladding is just going to have to suffer for fashion.

 

Winters here (baltics) are very dry though; so I don't think we're going to add too much humidity change added on top of the temperature swings. Airtightness is expected to be ok and vapour from inside minimal. The moisture will come from outside air at night.

 

End grains get painted. Visible faces get painted. Overlaps get painted. 30 cm of backside gets painted (the drip edge). The rest of the backside doesn't get painted to aid drying into cavity and save on paint. This article suggests coating on all six sides but given that the building isn't a sieve dumping vapour from inside I think ok to leave the back unpainted:

 

https://www.buildingscience.com/documents/building-science-insights-newsletters/bsi-015-stress-relief

 

 

For mental notes paint is ~€6 per litre and anywhere form 6-12 m2 per litre (assume 6) and there's double the area to paint that the wood covers due to overlaps etc. Works out at about 600 m2 per coat. 100 litres per coat. €600 per coat. Ouchy.

 

 

Fixing...


Here's where I'm least sure about the least worst approach.

 

 

Some say nail softwood cladding. Nails are cheap. Nails are fast.

 

Some say use one nail per "inboard" board (in the centre) and two nails per "outboard" board (at 25% and 75% of width, so nominal 37.5 mm and 112.5 mm on a 150 mm board) in order to avoid splitting the wood as it expands and contracts.

 

 

I don't like nails. They're a bit permanent for my liking. It is difficult to drive them "flush" at the best of times and arguably you want to "over drive"t hem a little bit to keep tension on the wood as it expands and contracts. Any "over driven" nails on the roof are going to catch water. It's more difficult to pull twisted banana boards tight with nails. (you've got to push the board down then nail it whilst holding it down) And you need fatter battens to show the nail who is boss (the pull-out strength out of the batten wants to be much higher than for the thing you are attaching with it) which won't let me use 25x75 mm battens.

 

 

I think screws are better.

 

Which screws and where though?

 

Lengths need to be ~50-55 mm for the "inboard" boards and ~70-80mm for the "outboard" boards and for the horizontal supporting battens to the house.

 

 

Really I'd like to use two screws on the "inboard" boards as they are the bendiest ones that want persuading into place. If we say nominal 140 mm width and 25/75% then these are at 35 and 105 mm. (35 mm in from the sides, 70 mm width between screws). That's right on the edge of my 30 mm overlaps. Could I push it to 25 mm and 115 mm so that the screws are under the overlaps, or is that +20 mm to 90 mm width between screws going to make a material difference to splitting?

 

Is it worth adding a relief groove or two to the back of these boards? (run "weathergrooves" down the back of them to "break their back" and make it harder for them to cup) Or is that going to make them more prone to splitting rather than cupping?

 

 

Should the screws have little heads or big heads? Do I need to buy coated screws given that they might be underneath boards and/or painted over?

 

 

I can buy "decking screws" that have little heads:

https://online.depo-diy.lt/products/7872#5578

https://online.depo-diy.lt/products/7872#5585

(1.9 cents each in 55mm, 2.8 cents in 75mm - with ribs under head but without ribs on shank)

image.png.c9b856cef3ee5ae8879acbf30b1e210a.png

 

https://www.senukai.lt/p/medsraigciai-4-2-x-55-mm-ruspert-zali-tx20-200-vnt/d251

https://www.senukai.lt/p/medsraigciai-4-2-x-75-mm-ruspert-zali-tx20-200-vnt/d25k?mtd=search&pos=regular&src=searchnode

(3.3 cents each in 55mm, 3.8 cents in 75mm - with ribs under head and on shank to clear out the hole in cladding board)

image.png.8772d747c0b03d884e879761d568aa29.png

 

I can buy "outdoor wood screws" that have larger heads, self drill tips, and under head/on shank milling cutters:

https://online.depo-diy.lt/productItem/134739/0

(2.7 cents each in 55 mm, not currently available in 75 mm)

image.png.f5338f77371a98d05feb201b23057c6a.png

 

Or indeed "wood screws" with larger heads, self drill tips, and under head / on shank milling cutters:

https://online.depo-diy.lt/productItem/5569/0

https://online.depo-diy.lt/productItem/5571/0

(1.5 cents each in 50 mm, 2.1 cents each in 70 mm)

image.png.2b9b8bf973554dc8171d44b2e0fa12c8.png

 

Or "screws for OSB" that have small heads and are essentially decking screws without the coating for that matter:

https://online.depo-diy.lt/productItem/134716/0

https://online.depo-diy.lt/search/4.2 65#134714

(1.1 cents each in 55 mm, 2.2 cents each in 75 mm)

image.png.da7af9f6317ff263bc2bba0cef32d8e9.png

 

Or go totally the other way with pan heads through pre-drilled clearance holes with their heads proud of the cladding:

https://online.depo-diy.lt/productItem/5975/6718

https://online.depo-diy.lt/productItem/5975/6718

(1.7 cents in 50 mm and 2centre in 75 mm)

image.png.d83e3a67c4929e8a84b094e9a5d254d5.png

 

Here's some side by side.

 

5x70 "outdoor wood screw" (5c each), 4.2x50 "outdoor wood screw" (2.7c each), 4.2x55 nice deck screw (3.3c each), 4.2x52 cheap deck screw (1.9 c each), 4.2x55 OSB screw (1.1c each)

 

PXL_20210627_182739559.thumb.jpg.839bfc075a77486eeb2cb9d32a769466.jpg

 

 

 

I have no experience here.

 

What's best for mauling recalcitrant softwood cladding into place without spitting it to pieces or pulling through the face? I've bought some to try but I can't recreate the weather cycles and some hard won lessons would be good!

 

Gut says painted deck screws or painted outdoor screws. The heads are VERY different sizes though.

 

 

Costs

 

I've added the costs for my own sanity as I'm going along here.

 

4.7 metre board supported every 450 mm with two screws is say 12x supports or 24x screws.

140 mm nominal width and 30 mm overlaps is 9 boards per metre is 216 screws.

16 metres of roof is 3500 screws. 2 sides to the roof is 7000 screws.

3.5 metre board every 450 mm is say 8x supports or 16x screws, 150 per linear metre. *26 is 4000 screws.

 

 

North gable call it 2000 screws.

Attaching battens to house call it 3000 screws.

Bad heads snapped dropped on the floor lost in the car or generally evaporated 1000 screws

 

Every cent on screw price is ~€170. I'm guessing <€600. Not the end of the world in any shape or form.

 

Paint €1800-2400.

 

Wood was €3000.

 

~10-15/m2 materials if I add blades and whatnot.

 

Labour.... ?

 

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Use your rough boards as the bottom layer, you won't see the edges when finished.  Use your good square boards for the top planks.

 

I used 150mm planks for the bottom layer and 100mm planks for the top layer.  Very little gap between bottom planks except where spacing between items makes it work by spacing a few planks to fit a particular gap.

 

I painted all my planks first coat before fitting then second coat once on, so if a top plank shrinks it will not expose bare wood.

 

Because they were being painted I used cheap 4mm by 50mm gold screws. You only see the screws on the top planks so space them nice and evenly and paint over them.

 

Only first wall done so far.

 

cladding_1.thumb.jpg.b3edda0ddeaac82069e891f10203ba0e.jpg

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Field update:

 

 

Screws

 

Painted fat screws all the way.

 

Decking screws are useless for persuading cupping softwood boards to meet their battens. They pull through the face before they pull the wood true.

 

Gold screws are useless for paint. Or, rather, all the good screws that have "milling ribs" under the head and on the shank (which you want to reduce splitting), are also waxed to ease installation. They don't take paint at all and removing it is a ball ache. Painted screws take acrylic paint no bother.

 

 

Paint

 

LOL at how decent primer and acrylic paint stick to rough sawn wood. 

If you rest two wet pieces on top of each other and after 24 hours they're as good as glued. The softwood tears before the paint peels; much the same as if you'd glued them together.

 

LOL at how well it sticks to the wife too. She appears to have turned into a Zebra... ?

 

Sand to remove fibrous material. Stiff brush. Prime. 2 hours. One thoroughly brushed topcoat of anthracite. (a cheaper off the shelf colour) 24 hours. Stack. Fit. Worry about how to do the final coat (with black) later.

 

Definitely brush this (stiff 4" fence brush) rather than trying to roller or spray it. You won't get good coverage on rough wood otherwise. If you're worried about acrylic hiding the texture of the wood don't be. It shows through nicely whilst softening some the rough sawn nature of it a little It's more visible in second coat black than in anthracite:

 

PXL_20210629_165704448.thumb.jpg.c6f3f35e3f6101fc9d5275f85eccd59c.jpg

 

We're painting ends to control the drying and hopefully reduce splitting. (a lot of the split ends you get are from the end drying faster than the middle of the board, and being unable to shrink far enough because the middle is still fat) They'll get re-trimmed and re-painted in situ but we figured it's worth painting the backs (for drip edge purposes) and ends (to control drying until they're cut and repainted)

 

 

Weathergrooves

 

Tedious but not as tedious as painting.

 

Buy a decent saw. (and go with the 1.6 kW 190 mm one not the 1 kW 165 mm one) Install your 8mm kerf blade of doom.

 

PXL_20210628_114524917.thumb.jpg.c0f4db9e196bac6572b758ff77952b9d.jpg

 

Lose the standard saw guide and rig something altogether uglier. Yes they're self drilling screws through the aluminium baseplate. Yes you could make something prettier but no I didn't as frankly a €90 inc VAT saw is a consumable and three holes are unlikely to make it useless for other purposes.

 

PXL_20210628_114530067.thumb.jpg.404036e8e5ba6e9aefb4d7c1af15beda.jpg

 

Quick jig hung off the side of the proof-loaded eventually-to-be-naughtliy-tall-deck frame. Leave space between your "width stop" and your "end stop" for the chips to fall through (else you'll always be cleaning out the corner)

 

PXL_20210629_093818022.thumb.jpg.2810d1fec41d1504626b9b33c1019952.jpg

 

 

Eat sleep groove repeat. Productivity is ~0.6 km/hour. Suggest 45 boards at a time for health and safety (vibration white finger) purposes - that blade being can be shoved along as fast as 1.6 kW will go (motor power is a limit even with the 125 dia on the 190 mm machine) but it doesn't have many teeth and the chips are huge.

 

PXL_20210703_205638930.thumb.jpg.eef14d3672c553acc83b761a608f3cf9.jpg

 

 

 

Wood

 

 

There was a day not so long ago that "double cut" used to be a log sawn into boards and shipped. These days it's a log sawn into boards, graded, all the A/B grade removed for reprocessing, and the C grade shipped as double cut.

 

We knew this but...don't under-estimate the labour involved in sorting through random mixed length C grade to find the best bits for each location. (long enough, and either one good face with two edges or one good face with four edges) 

 

I'm a little worried about knots and check marks. May need to invest in some flexible sealant for these where they're on the roof. We'll see what it looks like after a few heating/cooling cycles in the anthracite base before deciding.

 

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Really interesting post, it’s a bit overwhelming and by the end of it I had forgotten what questions you asked at the beginning  ?

I am really not sure about the whole groove cutting process….. but it looks like your committed, will be interesting to see how this works in real life……. 
I live in a coastal area and the only screws that have not failed are stainless steel….. but I have not used painted screws before - maybe something I should look into. 
I fixed my cladding with a single line of ss ring shank nails and have had no problems, I have both ship lap and board on board but my top board on the board on board  is just 50mm wide as I like the look. 

 

A269C84D-603D-4B17-8CF5-E3CCB0D8AA6E.jpeg

530EB8B0-FED2-4A46-B17B-6B043D0F03E5.jpeg

0722E13D-B488-40D4-BA60-40A15E0303E2.jpeg

9A4E0CAA-B76D-4F35-8274-330D2BFA40A6.jpeg

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Thanks CPD. This is probably as much thinking out loud and a mental note to my future self as anything else!

 

Liking the rusty wall ornaments on your build! ?

 

 

Mechanically the batten-on-board is a bunch more sensible from a "stop things moving / splitting" perspective. Those "inner" boards are fully supported across their width AND the "outer" battens are almost fully supported across their width. I quite like batten on board in darker colours. She who seems to know what rents / sells prefers board on board so I won't argue!

 

Here I think the batten-on-board tends to get used on the agricultural buildings that are open air. Board-on-board is the local look for residential buildings. I suspect that although mechanically it's inferior (you have less support for the outer boards to prevent cupping) it is usually fitted over horizontal battens mounted directly to the walls; and relies on the fresh air between the outer boards and the inner boards (which is ~100 x 25 mm on these rather than the 10 x 25 mm of batten on board) as your ventilation for the walls / roof. The walls themselves would have been logs with air etc between them.

 

 

 

In hindsight, if we'd planned board on board from the outset rather than planning corrugated bitumen then changing our minds at the 11th hour, and I was brave, we could have fitted horizontal strapping to hold the external insulation in place, with a through-insulation batten at the top of the wall / bottom of the roof to carry the cladding weight, then mounted this cladding direct to that batten and the strapping; with a roofing membrane (if any) draped over the horizontal strapping given how step the roof is. 

 

As is we have a through-insulation batten at the top of the wall / bottom of the roof, then external insulation held in place with vertical strapping, a breather membrane (so that we could leave the frame up for a while whilst deciding what to do, and as belt/braces for the cladding), then vertical battens as spacers and more horizontal battens before this cladding goes on... (a photo will make more sense later during first installs) Messy but that's what you get for changing your mind. At least she likes the deep window look!

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Screws or nails? I specify screws and then find the joiner is trying to provide his own nails or even nail gunning. NOOOOOH

The reason is obviously that nails are very much quicker and is what they are used to.

BUT good screws will cut a hole and reduce splitting, self countersink, adjust in our out, and come out again if necessary.

If a board cracks or distorts it can be adjusted or even removed without ripping the wall apart.

 

I only buy the ultra modern screws that do all these things. they seem expensive but there is no wastage, the slots can be used as often as necessary for in/out.

If  they have to come out again having hit a nail etc, then they are as good as new.

 

 I last bought Ulti-mate and they were almost a pleasure to use. Twice the price of the cheapies, but at 10p for an 80mm it is incredible engineering, and comes with a head that holds the screw at any angle.

 

Downside of a screw....the head is on show. 

 

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And re painting.

I have a house made of wood. It is painted white and needs repainting every 3 years, at least in part, when old layers spall off. I think there may be 12 layers there, and some were clearly paint onto dirt. Mostly it is heat or damp that causes the failure.

 

For a new building I would always prefer stain.

That said, the cheap brands take just as long to apply so I only use the big names.

 

For a neutral finish I choose 'oak' and it barely changes the colour of tanalised pine cladding. However there is a lovely sheen and the colour stays indefinitely.

I have often contrasted this with the 'almost black' brown, called dark palisander. In the shade it retains colour indefinitely, while in the sun it  benefits from a recoat in 10 years.

It never peels off.

 

Did you note that I have written tanalised not tantalised? I have added it to my dictionary to overcome spell-check.

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A wood clad roof!

 

I would not dream of this.

(There was one a few years ago, a school in the south-west, that won awards but, last I heard,  is  abandoned or demolished after a couple of years.)

 

It might be liked aesthetically, but would need a 'proper' roof underneath it to keep the weather out, then allow for replacing the timber every few years, or considering it a green roof.

 

On a wall we leave an air and ventilation gap behind for the inevitable leaks. On a roof the leaks will be greater in number and quantity. 

 

So if you must have wood 'cladding' on the roof, put a steel roof on first. 

 

Oh, and then don't bother putting on the timber.

 

Purely my opinion you understand, but I would politely decline to either design this or build it for a client.

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4 hours ago, saveasteading said:

So if you must have wood 'cladding' on the roof, put a steel roof on first. 

 

Oh, and then don't bother putting on the timber.

 

Purely my opinion you understand, but I would politely decline to either design this or build it for a client.


wise words I feel…… 

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22 hours ago, Cpd said:

Really interesting post, it’s a bit overwhelming and by the end of it I had forgotten what questions you asked at the beginning  ?

I am really not sure about the whole groove cutting process….. but it looks like your committed, will be interesting to see how this works in real life……. 
I live in a coastal area and the only screws that have not failed are stainless steel….. but I have not used painted screws before - maybe something I should look into. 
I fixed my cladding with a single line of ss ring shank nails and have had no problems, I have both ship lap and board on board but my top board on the board on board  is just 50mm wide as I like the look. 

 

 

 

 

9A4E0CAA-B76D-4F35-8274-330D2BFA40A6.jpeg

So how does that work?

 

Your single nail fixing by reckoning goes bang into the gap between the bottom layer boards?

 

So either you are trusting to luck a bit, or you used long nails to go through the top layer, through the (gap in the) bottom layer and into the battens?

 

Me, I have wider top boards fixed with pairs or screws that just screw into the bottom boards.

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It's a reasonably mad thing to do.

 

Less mad than a thatched roof. (those poor souls without trees)

 

Less mad than a horizontal deck. (what are people thinking)

 

 

Practically the membrane handles the rain fine. We had over two inches today (30C and clear skies the rest of the week...brutal) and it's bone dry below that membrane. 

 

It won't handle the UV in the long term though or the weight of the storks perching on it waiting to collect all the frogs after the rain stops etc.

 

That's what the wood is for (UV barrier and the mechanical protection). The paint / grooves are to then keep the wood decent for as long as possible. 

 

If it fails...whilst we still own the place...I'll chuck the usual rukki roof at it. ?

 

 

The Swedes can't make their minds up which way the grooves go (groove up to stop water going onto lower boards or groove down to create a bigger capillary break). My cutter is square so have done with groove down. (Google translate works well)

https://www.traguiden.se/konstruktion/konstruktionsexempel/tak/underlag-av-trapanel/faltak/principlosning/

 

MTS have some plausible sounding guidance:

http://www.woodcomponents.ie/wp-content/uploads/2016/03/MTS-Cladding-Detail-and-Design.pdf

 

The Kiwis make a point of one fixing per board only.

https://www.renovate.org.nz/1970s/walls-and-cladding/wall-cladding-original-details/timber-cladding/

https://www.buildmagazine.org.nz/index.php/articles/show/vertical-board-cladding

 

 

@ProDave you're supposed to fix to the battens to allow the boards to move. Timber expands and contracts a lot across the grain. If you fix the boards to the battens then each board can expand and contract independently (sliding a little). If you fix the boards to each other they don't have anywhere to go when they expand and contract. Something has to compress/buckle or stretch/split. One fixing per board (rather than two) reduces the tendency to split even further. This single fixing doesn't work for wide boards on the top though.

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As above, the boards need to be independent to move as needed, it’s pretty easy to pre drill a hole in the centre of the top batten so that your nail has the best chance of going through the joint in the boards below, should it miss it will only go through the very edge of the lower boards and any spitting due to expansion and contraction will be hidden behind the top batten. I have done the back of my cabin like this and it’s been up for over six years without any boards spitting, the same with my shiplap single line nailing, totally stable after 6 years with absolutely no splitting. All the holes on both the shiplap and vertical cladding are pre drilled, the shiplap are oversized by a mm to allow a tiny bit of movement. I have seen lots of board on board with spitting and cupping and that’s why I use this system - it works and has not failed me yet and I like the look. 

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On 05/07/2021 at 21:33, Cpd said:

I have not used painted screws before - maybe something I should look into. 

 

It works. In fixing steel roofs the best bet is an integrated nylon head the same colour as the roof. Plastic caps fall off.

 

Once though had a very large roof that was a special colour. Hilti dipped all the screws (and washers) in the right colour of paint. I expected it to come off in the tek gun or over a couple of years but it didn't. Presumably they knew what paint to use.

 

For timber screws I have simply primed and painted over screws, and it usually works. It shouldn't show from any distance. Yellowish screws on pine. silver on white and it may not need paint... not sure with brown or black.

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Doesn't work if screws as waxed sadly. Might get away with it with Toolstation / Screwfix silver/gold screws but everything I find here is waxed by default for installation purposes.

 

Except black phosphated plasterboard screws or silver sheet steel screws. Don't want those though! (high strength and easy to paint the heads but brittle and rust within the wood in the case of plasterboard screws)

 

 

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Ruddy 2021...if you see half a dozen screws...then try half a dozen screws...don't expect the same half a dozen screws to be in stock the next week or ever again! Have sourced another two screws to try. Cheapie goldscrews hopefully without wax this time. Fancy C3 rated torx screws that will definitely work but haven't found in 70 mm yet.

 

 

Need to think how to get these up on the roof AND paint them. it's a 9:12 pitch (37 degrees) and I wouldn't want to walk that / would rather avoid smashing freshly painted boards with a ladder laid on it if possible.

 

 

I think order of operations (critique welcome) should be:

 

- Fix 25x70 battens to roof using some 'standard' waxed screws that don't need pilots

- Pre-cut the ends of all roof boards square. Pre-drill all the roof boards using a jig.

- Pre-mark the battens for width (where the every board should go)

- Roof monkey at the ridge, Ladder monkey on the ground, and throw a rope with a noose to hoik the board up onto the roof

- One string at the eaves to line up the ends of all the roof boards for "height"

(maybe make that an "end stop" so that the boards just slide down the roof into position and we need only get the width right?)

- Ladder monkey at eaves lines up the width AND the "height" and pops a screw into a pre-drilled hole

- Roof monkey at the ridge lines up for width and pops a screw into a pre-drilled hole

- Rinse and repeat x150

- Roof monkey pops in the rest of the 4.5 x 50s or 5x50s holding these boards on through pre-drilled holes

- Roof monkey can still climb up and down the 9:12 roof using the ~90 mm gaps between boards and the battens

- Roof monkey does second / final coat of black on these "inside" roof boards; on the top face including screws AND the weathergrooves

 

- Predrill AND pre-paint the "outside" roof boards

- Definitely fit an "end stop"

- Noose the "outside" roof boards the same way but stack them somehow? (four boards in a gap, every 4th gap?)

- Roof monkey takes their time fitting all the screws AND painting each screw with a dab of paint after it's installed (to paint the screw and seal it to the wood as much as is possible)

- The roof largely remains climbable even though all the boards are up there

- I can tie a ladder to an "overhang" for when we get to the ends. There is an area of roof at the end (gable overhanging the deck) we are not boarding until later (when we source the deck materials and the underside of the roof materials - not for some time yet)

 

 

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The postage to Lithuania would be a bit much ? 

 

No milling heads or shanks on those so they'd be as liable to split the timber as regular goldscrews too.

 

I think my wife has sorted a supply of the 70 mm ones without going to the 8 cents a screw place ?

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  • 2 weeks later...

And here we go...

 

After much head scratching forget about trying to line up roof and wall boards. Unless you designed the openings to site your cladding pitch you're never going to get them to like up and an uneven roof is obvious from a mile away.

 

Make a jig to space say five boards at a time. Fit every 5 the one, checking from a datum every 25th. Go back and fit the others.

 

Fit them roughly in position up/down wise only left right matters. You sort endd when she.

 

Fixing centres 45 and 95 on a board that's 140ish mm wide and has a 30 mm overlap works for undoing cupping and twist.

 

5*50 mm screws for these boards. Battens are 25*70 mm (reject cladding slit into two) use cordless drill not an impact for setting the screws.

 

And if you've got good shoes (e.g. hiking boots / vibram sole then rough sawn timber is walkable at 9:12 pitch (37deg) which was a surprise. 

 

PXL_20210717_182814976.jpg

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On 06/07/2021 at 21:34, markocosic said:

 

The Swedes can't make their minds up which way the grooves go (groove up to stop water going onto lower boards or groove down to create a bigger capillary break). My cutter is square so have done with groove down. (Google translate works well)

https://www.traguiden.se/konstruktion/konstruktionsexempel/tak/underlag-av-trapanel/faltak/principlosning/

 

Kind of... grooves up are the traditional way, grooves down are an alternative, but the important detail is in which to use depending on the cupping of the boards once they're installed. If installed so the top board cups out, meaning water will run towards the edge, then the groove is outwards. If installed so that cupping is prevented, the groove goes to the inside to prevent capillary action under the boards.

 

Personally, I do wonder about the obsession with screws. Nails are, believe it or not, absolutely fine - tried and tested.

 

It's a great site for details, a lot of it builders here in the UK could learn from for timber frame detailing.

Edited by SimonD
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Thanks - good to know there's logic to groove up vs down.

 

On screw Vs nail:

 

If we'd planned to have board on board cladding from there outset I'd have had 195*45 mm studs filled with mineral wool, then 45*45 horizontal battens every 600 with mineral wool fill, and a 95*45 at the top of the wall, then membrane, then 25*50 horizontal battens on top of the 45*45s. This would give 70 mm depth to nail into. 90 mm nails would then work a treat. Having seen board on board of have no issue with the battens being horizontal and the only breathing being in the ~80*22 mm space between the boards.

 

 

As it is we planned to have lightweight cladding (wriggly bitumen) so the structure wasn't built for it (it has just a 45*45 at the base to take weight then 25*100 vertical strapping to retain insulation so is being adapted. 

 

The wood is awful too thanks to their yanks buying up everything this season. (all sapwood, lots of knots, only one "good" face, with cupping the least of your worries vs splitting, twisting and bending, insect damage, etc)

 

So I'm using the "bad"  cladding slit into two 25*70 mm pieces as my battens (you can manhandle a 25*70 into shape as you screw it to the building). This isn't thick enough to take nails.

 

Then we're manhandling the 25*140 pieces into a straight line and planar shape as we go. Foot in 80 mm gap. Twist to un-bend plank across 140 mm width. Shove 5mm screw in to pull it tight against the batten.

 

Very little chance of getting it all held in a reluctant position AND gunning a nail in before it moves / in a vaguely straight line.

 

 For DIY folks you can take your sweet time with screws, undo it easily if you make a boo boo, and you only need the 25 mm batten not the 45 mm you'd want for nails.

 

 

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23 hours ago, SimonD said:

 

Personally, I do wonder about the obsession with screws. Nails are, believe it or not, absolutely fine - tried and tested.

But using just 25mm battens and counter battens, they are too bouncy to nail into, hence screws being preferable.

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On 19/07/2021 at 10:51, ProDave said:

But using just 25mm battens and counter battens, they are too bouncy to nail into, hence screws being preferable.

Yeah, you see I've not had a problem with that. I've just fitted about 116 m2 of cladding all nailed on 25 x 50 battens. This install did have 47 x 47 battens behind, but I don't think it's any different from clouting slate tiles onto 25mm battens on a roof.

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