dnoble

Board-on-board or "hit and miss" cladding

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I'm thinking of doing this. Usually with vertical cladding one needs vertical counter battens. This site suggests you don't for board-onboard because there's a void at the front. BUT the battens need to be angled forwards.

My question is, where can I get cheap treated battens which have a 15deg angle machined in or would I have to get them specially made (which will probably negate the benefit of not needing vertical counter battens)

https://www.tdca.org.uk/timber-cladding/cladding-design-detail/vertical-cladding-new-buildings/

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I think a counter batten is beneficial in more ways than just moisture, plenty of airflow to dry out the boarding 

for the cost and time it takes to fit a counter batten I can’t see it being much cheaper to find chamfered battens

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Agree with Russell, but if your determined to go the other way then just cut a 150mm sarking board with whatever angle you like down the middle  to create aprox 73-74mm battens. Did this for my shed and it worked really well. 

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Thanks

Those are both good points. 

Sarking board cut down middle is a good idea (though extra work as I'll need loads, plus they'll need treating on cut edge)

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How much water is actually going to pool on top of the batten if it wasn't angled? I would just use normal square batten and have done in the past for exactly the same build up. Angled could be argued as being better but I think it's very marginal with overlapped boards. 

 

More importantly is to lay the top boards so that they 'cup' inwards and clamp on to the base board for a snug fit, with sawn wet boards at least. 

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I used 25mm vertical counter battens- my site is exposed and wet so I didn't want to cut any corners. I also laid my breather membrane in vertical strips, so each joint was overlapped at a batten to hold it down securely.

TRADA suggest a minimum of 12mm for roofing counter battens, so I presume you could use the same gap on a wall buildup. Perhaps just a packer of 12mm WBP/OSB at each batten fixing point? The downside is that there is no continuous batten pinning down your breather membrane onto the sheathing.

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Posted (edited)

Re ventilation of rain screen cladding on framed buildings, the guidance in BS5250:2011 is that you have at least 500sq.mm of ventilation to the outside per linear metre of wall.

Edited by Ian

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Roofing battens are cheap and super treated. I agree with @Miek no water is going to pool for any time behind overlapped board especially if you have counter battens which imo is a must.

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On 16/04/2018 at 19:39, Miek said:

More importantly is to lay the top boards so that they 'cup' inwards and clamp on to the base board for a snug fit, with sawn wet boards at least. 

 

Hi Miek

 

Thanks for this advice. What's the trick to making sure they "cup" inwards. Presumably it's to do with the orientation of the grain?

 

The advice from the cladding site is that counter battens not needed with board on board (though it does suggest using angled battens). 

Is the feeling here that I'll need to counter batten if using normal square battens? It's going to be a fairly sheltered site with trees and overhangs providing extra rain screening etc.

(I want to keep things simple/cheap if possible)

 

 

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2 hours ago, dnoble said:

 

Hi Miek

 

Thanks for this advice. What's the trick to making sure they "cup" inwards. Presumably it's to do with the orientation of the grain?

 

The advice from the cladding site is that counter battens not needed with board on board (though it does suggest using angled battens). 

Is the feeling here that I'll need to counter batten if using normal square battens? It's going to be a fairly sheltered site with trees and overhangs providing extra rain screening etc.

(I want to keep things simple/cheap if possible)

 

 

Yes it's about grain orientation. You want the first layer to curl away from the wall, and the second layer to cup towards the wall, so the two lock together. Although I've found in practise there isn't a whole lot of movement anyway, and a lot of my boards came quarter sawn so it was six and two threes.

The other thing, if you're wanting to be a perfectionist, is to look carefully at the angle of the knots. Sometimes they are completely perpendicular, but often you will find that the knot runs at an angle, and you want that angle to be pointing downwards. The idea is that if the knot ever falls out, it will leave a hole that sheds water away from the building, rather than one that funnels it in behind the cladding.

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Thanks for the replies

 

I'm cladding it with larch from a local sawmill just over the bridge in south wales.

I was surprised to discover that hit + miss boarding was about half the cost of milled shiplap, and quite a lot less than plain square or Waney Edge boards.

thanks for the info about grain orientation. Hadn't realised it also applied to the lower layer, but this makes sense

The boards are 150mm for the lower and 100mm for the upper layer with a 25mm overlap on each side (150mm boards being 50m apart)

It'll be interesting to see if I can ascertain the curve of the grain in pieces this small.

 

Sounds as if  counter battening with roofing battens is the way forward, and you're right they are pretty cheap. 

what's the difference between the blue and red ones.

I'm assuming it's for boy and girl roofers?

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“I think”Both blue and red are just dyed to show that they have been graded for use on a roof, (health and safety)  and cost far more than bog standard roofing battens. I would just use the standard treated batten as its going to last just as long. You will need to have everything ready to go when it comes to cladding as the spring / summer is not the best time to be using fresh cut larch, it will start to warp and change shape fairly quickly if its hot dry weather, you may be ok with using narrower boards but i was using up to 350mm waney edged larch in really long sections.....  it all went well and its such a lovely wood to work with. I painted mine as i wanted a cleaner looking  finish. Use the biggest ss ring-shank nails you can manage as anthything less will pull. @Crofter and others will probably have more relevant advice as they have done the same style.  

558C3524-43C7-45D3-9A72-1299BE9E049A.jpeg

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Posted (edited)

Think from memory I used 63mm ring shank nails in the nail gun...not too long or you'll puncture the vcl. Counter battens at 2x25 plus the thickness of the board and your fine.

 

Edited by Tennentslager

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9 minutes ago, Tennentslager said:

Very nice hut you got there @Cpd😋

Thanks, love building stuff....... 

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I've noticed very little curling of the boards, either in storage or after installation. But mine are only 100x20mm, maybe wider boards are more susceptible.

I did eventually start pilot drilling and hand nailing anything within six inches of the end of a board, it's massively slower but I was getting a few splits along the grain. An added bonus on the second layer is that having the first two nails poking out helps locate the board into the gap.

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4 minutes ago, Crofter said:

 

I did eventually start pilot drillin

Yes i drilled all the holes and hand nailed everything as i dont have a nail gun, only one line of nails per board in my case to prevent splitting as the timber dried. 

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I nailgunned everything! My boards were 150x 15 but very moist. Nails one inch from the edge at a 45/50° angle in towards the centre of the board.

Once you've done a few you get a feel for the wood and read the knots and grain....too near a knot and move or miss it out. Battens at 400 or 600 spacing means loads of nails per board.

Practice on the under board as it's all getting covered anyway. Use all the damaged edge stuff underneath too.

Mix the colours up randomly.

Keep the best boards with good grain for corners.

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The red and blue battens are a grading system so it is easy to tell they comply with a certain British standard, you can still buy plain tanalised green battens, which will be fine for what you need and will be even cheaper. 

 

 

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My local BM stopped doing normal battens and now only does blue ones- so I had to use them even on internal work. Annoying, cos the blue stuff comes off on your hands, and I found them very prone to splitting compared to regular ones.

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