Deck Board Stiffness
Obviously the boards with the grooves on left of pic will weigh less, but do the grooves make them stiffer in the long direction as well?
Anonymous
8/30/2025, 9:50:48 PM
No.2941916
>>2941915 (OP)
here let me search that for you since its so much more effort than making a thread with a stupid question instead of asking in the general
https://presearch.com/search?q=why%20are%20deck%20boards%20grooved
Anonymous
8/30/2025, 10:13:12 PM
No.2941919
>>2941986
Seems like all the results are about edge grooves, or minimal depth face grooves. Having a hard time finding info specifically about these deep grooves on hidden side. Maybe "grooves" is not the right term.
Anonymous
8/30/2025, 10:46:21 PM
No.2941926
>>2941944
>>2942034
>>2941915 (OP)
Stiffer than what? My dick? Lolno. Even at 50+ my dick mogs that board. But seriously, how is a board with material removed going to be stiffer than a board that's still complete? It may be almost as stiff, but weigh less, but it won't be any stiffer.
Anonymous
8/31/2025, 1:28:26 AM
No.2941944
>>2941966
>>2941926
Probably the same reason corrugated cardboard is more stiff and resistant to bending than solid card of the same weight. Or an I-beam is stiffer than a box tube of the same weight. It all depends on the forces involved and what angle/point they act on the material.
Anonymous
8/31/2025, 2:35:24 AM
No.2941953
>>2941968
none of them seem to be wood?
Anonymous
8/31/2025, 3:18:07 AM
No.2941966
>>2941944
Cardboard is already a corrugated material, that's like triple the variables, and an I beam is a totally different shape than a box tube. Be real here.
Anonymous
8/31/2025, 3:24:52 AM
No.2941968
>>2942328
>>2941915 (OP)
The solid ones will be stiffer in all directions, they're significantly heavier to get that stiffness, but they are stiffer.
>>2941953
Composite deck boards my dude. They're expensive, but they look nice, and last forever.
Anonymous
8/31/2025, 5:01:29 AM
No.2941986
>>2941995
>>2942442
>>2941919
>Maybe "grooves" is not the right term.
They call it "scalloping"
Anonymous
8/31/2025, 5:07:49 AM
No.2941988
>>2941915 (OP)
if everything else is the same, yes
Anonymous
8/31/2025, 2:59:20 PM
No.2942034
>>2941926
>It may be almost as stiff, but weigh less, but it won't be any stiffer.
I think this is correct, but only if the material is homogeneous.
If the skin/veneer is significantly stronger than the infill, it would be stiffer with the scalloping, since there is more of the strong material at the perimeter.
Anonymous
9/1/2025, 1:29:26 PM
No.2942211
just frame 12" on center and you won't have to give a shit.
Anonymous
9/1/2025, 5:32:13 PM
No.2942231
>>2941915 (OP)
Deck boards are made stiff by the joists underneath. Joist spacing is reduced if you're a cunt and want your deck boards laid out diagonally.
Anonymous
9/2/2025, 2:19:20 AM
No.2942328
>>2942343
>>2941968
they make the wood under them rot and the whole deck falls apart anyways
Anonymous
9/2/2025, 3:57:31 AM
No.2942343
>>2942328
Tape your deck joists, and seal your cuts.
Anonymous
9/2/2025, 3:56:23 PM
No.2942442
>>2941986
>Trex™
Green light! amazing
>TimberTech
WARNING WARNING air raid sirens
Anonymous
9/2/2025, 7:48:36 PM
No.2942473
>>2941915 (OP)
They are less stiff
This is a good thing, as it prevents breaking/shattering on impact
Anonymous
9/2/2025, 8:08:55 PM
No.2942479
When using composite decking you want 12" OC joist spacing. Treated wood decking is fine with 16" OC, but the composite stuff will flex with that joist spacing, especially when it's a hot day in direct sunlight.
As for your question about the grooves, if the boards are the same thickness, the grooves will lower their stiffness as the cross section has less area. But only marginally, really. The grooves on the underside are there solely to lower the manufacturing costs because it uses less material per board foot. It's why you only typically see it on the less expensive decking.