# Forum Home Renovation Stairs, Steps and Ramps  ext hwd stair tread cupping/growth rings

## russ34

which way do i align the end grain growth rings on the treads to minimise cuooing that will collect rainwater? like a rainbow or an upside down rainbow?

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## journeyman Mick

Like an upside down rainbow. 
Mick

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## Honorary Bloke

> Like an upside down rainbow. 
> Mick

  Are you sure, Mick?  :Confused:

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## Metung

Remember Bob that your a northern hemisphere bloke where even the water goes down the plug hole the wrong way. :Wink 1:

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## journeyman Mick

> Are you sure, Mick?

  99.9999% sure.  :Smilie: 
From memory timber cups away from the centre, therefore fixing the treads "upside down rainbow-wise" has the centre at the top of the tread and the cupping at the bottom. Mind you, it's been a few years since I've done that type of work and the last few years have been pretty stressful, so I might be mis-remembering things. :Rolleyes:  
Mick

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## Honorary Bloke

> 99.9999% sure. 
> From memory timber cups away from the centre, therefore fixing the treads "upside down rainbow-wise" has the centre at the top of the tread and the cupping at the bottom. Mind you, it's been a few years since I've done that type of work and the last few years have been pretty stressful, so I might be mis-remembering things. 
> Mick

  OK, that's what I meant. To me, an "upside down" rainbow would be one with the centre at the bottom, as rainbows naturally have their centre at the top, at least here in North America.  :Rolleyes:  :Rolleyes:  :Biggrin:   We are in agreement with the method, just not the semantics.  :Smilie:

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## Bleedin Thumb

I always thought that timber cupped "towards" the centre. :Confused:  Are you sure Mick?

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## Vernonv

Mick's talking about the center of the timber (well, the log it came from) and you're talking about the center point of the rainbow ... c'mon HB, get your head out of the clouds :Biggrin:

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## chrisp

It's an interesting problem.  I think Mick and others are correct in regard to the question posted by the OP.  However, I've heard (secondhand, so I could be wrong) that old timber bridge builders would place the timber the other way (rainbow up) as it was common of the centre (of the log) to rot out (and collect water) if placed upside-down rainbow.  I'm not sure which is correct as rainbow-up will result in a concaved top that will collect water as the timber dries out!

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## glock40sw

> I always thought that timber cupped "towards" the centre. Are you sure Mick?

  Correct.
For Hardwood treads, The smallest ring should be facing down ie: on the bottom.

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## Honorary Bloke

> Correct.
> For Hardwood treads, The smallest ring should be facing down ie: on the bottom.

  Whether this represents rainbow up or down, this is what I meant to convey. Thanks Glock.  :Smilie:

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