Hello all,

My customer is convinced that decking--exterior decks and interior T&G car decking--should be installed exactly opposite of what I've always done and everyone I've ever worked with.

Which way up, and why?

And finally, when your customer emphatically knows that they are right and have done it that way since the dawn of time--and you've warned them why you don't put the wrong side up--do you bow to them when your name is on the finished product?

And what if the customer is your father?

By the way, I won't quote you. I'm just trying to rest my soul.

Thanks,
Zach

oh boy... I've heard and been convinced of both ways here. I still like to look at the end grain and think of it as an umbrella... in other words heart down.

Hi all,

Seems to me like everyone has his own idea...

Basic shrinkage as taken from Wood Handbook (Forest Laboratory) Sorry for that big image but it's important to know.


Below you can see two different options - heart down (left) and heart up (right).

If you install boards heart down you'll get a bowl full of water (whenever it rains) in every plank.

As I believe, the solution is to install planks heart up for two main reasons:

• flat planks - you can get rid of bowing by cutting grooves as shown
• strength - end grain has better abrasion resistance and will last much longer. And even more, using hard brush to remove sotf grain will make a great (nonslip) texture

Looking forward to see more in this discussion
Best,
Michal Zajic
TFDesign.cz

Heart down, the flooring will wear better and be far less splintery. An old carp told me when building bleachers and benches to put the heart side up for the visiting team side for an enhanced pine splinter experience. The FPL has a pamphlet on the subject.

Weathered cupping effects are more the result of moisture and solar heating of the exposed side than grain effects.

Thanks for your ideas.

I've been asking around outside the computer, too. Also been looking at installations, old and new.

I think everyone is right, at the right time. Here's my theories.

Michael hit it on the head for green lumber. It will cup like crazy as it dries out, even in this very wet climate. Not only will it cup and hold water, the decking has a built in see-saw for creaking and working fasteners.
Heart up is the only way for green wood, or heart out for fascia.

The other argument for heart up is when sapwood is present, which rots regardless of species.

Kiln-dried or air-dried, then milled seems to make a difference. Treated decking, which must be dried before dunking in major chemicals, actually cups the other way in our humidity.

As for splinters and shaking, the heart does in some species, treated yellow pine is the worst I've seen, and varies per lot.

As for car deck T&G overhead on ceilings, if it's dry or not, seems like heart up makes sense to avoid shaking and splintering on the visible side, the sap side.

Anyone else have any theories?

Zach

I have installed stair treads both ways and it always cups up. I have given up on following the diagram in Michal's post. Heart up does not wear as well. The key is to seal all sides of the wood, fasten it well and if using 2x stock, kerf the bottom. Cupping is definitely due to weathering on exterior stair treads. The sun dries the top and the bottoms stay damp. The treads on my shady north stair haven't moved, while the south ones I am going to go back and screw'em down and plug them.