End Grain Splitting

[Chunky Monkey]

Hi All,

I've made these fluted covers to hide the frame work on my timber orangery, there's 8 in total, however 50% of them now have splits in the end grain.
Is there a way I can stop this? Is it down to poor design or poor choice of timber (Sapele) or is it simply inevitable? The panel is 27mm thick, the depth of the flute is 9mm, the Sapele has been air dried at the yard and then here for approx another 12months. (As an aside, I am finding the Sapele moves with moisture changes much more than I was expecting)

Thanks for any advice
Jon

 

[Cabinetman]

Hi Jon, sorry to say this but I think it’s purely down to the way you’ve screwed it to an immovable underframe, the timber is contracting or expanding depending on the weather and it hasn’t got anywhere to go except to split, I think those splits will grow much longer and go further up the planks yet. How to resolve it won’t be easy without a rethink. What exactly are those fluted boards covering pls?

 

[Doug71]

Wood always dries out quicker at the ends, I use end grain sealant on loads of things these days, I think it's really marketed as stopping water ingress but I presume it must also stop things drying out as well.

https://www.reddiseals.com/product/end-grain-sealant/

 

[Chunky Monkey]

What exactly are those fluted boards covering pls?

I tried to allow for movement, by using a 5mm pan headed screw in an 8mm hole but, having seen how much the Sapele moves, I now suspect this is not enough.

This is what the boards cover.

Jon

 

[eribaMotters]

It's a shame you cannot just have one central screw fixing. Whilst the end grain would still possibly split the panel could at least expand and contract and minimise the problem.
Other solution would be to use exterior mdf. I've used MR mdf with a t&g v groove detail on garage doors. 20 years later, no movement or damp issues and water based paint finish holding up well given a wash and single recoat every 4 years. Initial primer coat was however oil based aluminium primer.

Colin

 

[Adam W.]

Which direction are these windows facing ?

 

[Spectric]

Cabinetman I think is right, something is moving and your covers are fixed on both sides and so have spit at the weakest point(thinest due to flutes). I would have either fixed only in the centre or used just a decent adhesive/sealer like EBT.

 

[Adam W.]

Cabinetman I think is right, something is moving and your covers are fixed on both sides and so have spit at the weakest point(thinest due to flutes). I would have either fixed only in the centre or used just a decent adhesive/sealer like EBT.

That's about right. I was wondering if they were facing into the sun too.

 

[Chunky Monkey]

Which direction are these windows facing ?

They face South East so get the sun from sun rise through to around 5pm, great for the orangery but not so great for wood movement

I would have either fixed only in the centre or used just a decent adhesive/sealer like EBT.

I am considering the adhesive/sealer route, I used CT1 regularly but still only as sealer, I've never really explored its properties as an adhesive. Mike G has just built a greenhouse using Hippo 3 for it's long open time, and I believe CT1/Hippo3/EBT is all the same technology. Maybe it's time I tried it on a test piece

 

[Cabinetman]

Love CT1, saw a video of the guy sticking bricks together underwater with it, not sure why you would ever want to do that but still, it’s brilliant for all sorts of things, whether it would have enough give when the timber shrinks and expands I don’t honestly know, I hadn’t realised Jon that you had allowed for expansion with the screws – good try but obviously things are moving more than I would have imagined. Ian

 

[Sgian Dubh]

If plenty of allowance has been included for expansion and contraction with the fixings, i.e., as you describe, a 5 mm screw into an 8 mm hole, it seems there might be another possible cause. The splitting you show is at the end of the board, and coincides with the deepest part of the fluting, which may or may not be coincidental.

Is it possible that the split end comes from very close to the original end of the board prior to you machining it? End shakes are common in seasoned wood, and usual practice is to cut this off, plus an additional 50 mm or so. End shakes can extend further than the visible evidence of them in the raw board state, and can reveal themselves later when the wood is in service. South east facing exterior location might equal significant drying potential which could also reveal any previously unseen end shakes.

Of course, I could be completely wrong, but I thought I'd mention it for your consideration. I've obviously no knowledge of how you selected and processed the material. Slainte.

 

[recipio]

Can you take them off and clamp the splits closed with a waterproof glue. ? Then reinsert with a sealer on the end grain.

 

[smackie]

I’d always been taught to nail fascia boards to allow for movement. I’ve seen wide facia boards nailed in a zigzag (i.e. wide left and right nailing but not directly level) to avoid creating tension straight across the grain. External wood fascias move a lot more than you’d think and the fluted bottoms are a stress point - if I was remaking them, I’d match the fluting to the top and leave a section at the bottom full thickness...