Which way round for T&G

[Argonaut]

I am cladding horizontal ceiling with t&g softwood.
it has v-profile on both sides, so can be fitted either way up.

The board will want to cup in the direction of downwards facing growth rings, so is it best to fit with growth rings upwards so edges pull tighter against the next board, or growth rings downwards to try and pull edges up when you fix

I recall reading there is a right way for T&G but can't remember.


Simplistic sketch attached

 

[Phil Pascoe]

It cups away from the pith.

 

[Argonaut]

It cups away from the pith.

Not sure what than means .... I put a straight edge on the boards just delivered they have a very minor 0.25mm cup as per diagram.
Just wondering do I fit growth rings facing up or down

 

[Sachakins]

The pitch is the middle of the growth rings.
How long have you had the boards.
If only just I'd lay them in the room your going to use them in, with sticks between them to acclimatise and see how they look in 3 or 4 days.
Then I'd fit with cup up to ceiling.

How are you fitting them?
Hidden pins through the groove, or pinned through face and filler then sand and stain or sand and paint?

 

[Tony392]

T and G Male section is upright on a horizontal plane it allows water to escape

 

[Argonaut]

T and G Male section is upright on a horizontal plane it allows water to escape

As per OP - these are being fitted to a horizontal ceiling, I can understand your response if it were on a vertical wall.

 

[Argonaut]

The pitch is the middle of the growth rings.
How long have you had the boards.
If only just I'd lay them in the room your going to use them in, with sticks between them to acclimatise and see how they look in 3 or 4 days.
Then I'd fit with cup up to ceiling.

How are you fitting them?
Hidden pins through the groove, or pinned through face and filler then sand and stain or sand and pa

Boards arrived today - special order to get clear treated boards.
This is going to outside open sided building - so no walls. hence no room to put it inm, to acclimatise.
It's putting a ceiling on the structure in the pic.
The intent is to glue line on rafter using Polymer glue and hidden nail through the tongue. As long as that feels solid enough.
Finish will be clear stain, so the fewer filled holes the better.

 

[Sachakins]

If the glue is going to be your primary securing method and pins to hold in place as glue dries, then I'd change and go cup down. Since cup up could leave gaps along glue line.

 

[Jones]

If the treatment was water based I'd give it at least a fortnight drying before fixing. If it's solvent based ( you'll be able to smell) then it'll still need a few days. I would fix cup up if it's noticable but the main criteria for selection would be best face.

 

[Argonaut]

If the glue is going to be your primary securing method and pins to hold in place as glue dries, then I'd change and go cup down. Since cup up could leave gaps along glue line.

I was just going to pin, was advised add a bead of polymer glue to each joist will be worthwhile, then screw nail through tongu.
I have bought stainless steel pins for the fixing

 

[Sachakins]

I was just going to pin, was advised add a bead of polymer glue to each joist will be worthwhile, then screw nail through tongu.
I have bought stainless steel pins for the fixing

It will easier to skew nail if cup face up, with cup face down more likely to cause a split, as there could be a gap between joist and cladding.

 

[Argonaut]

It will easier to skew nail if cup face up, with cup face down more likely to cause a split, as there could be a gap between joist and cladding.

Thank you

 

[trvlr]

erm konphused.... what exactly is the "cup" o T& G boards?

 

[Argonaut]

Boards are cut flat .... but within Hrs all boards start to cup, Cupping is a wood floor’s natural reaction to moisture. T&G tries to retrain this by interlocking of the boards. Wood warping - Wikipedia

 

[LeeAkeroyd]

Not sure what than means .... I put a straight edge on the boards just delivered they have a very minor 0.25mm cup as per diagram.
Just wondering do I fit growth rings facing up or down

The boards will usually cup in the opposite direction to the picture which you originally uploaded.

 

[paulrbarnard]

If the glue is going to be your primary securing method and pins to hold in place as glue dries, then I'd change and go cup down. Since cup up could leave gaps along glue line.

While your answer is good based on what the OP aside I think it is the wrong approach for the project.

Cup down will always look wrong as you get harsh transitions between the boards, rather like a saw tooth with the sharp edge facing out from the boards. Cup up results in more of a wave effect that looks less like a mistake.

Personally I would not use glue in this situation and just Use the pins.

 

[Doug71]

The direction of cup depends if the board is taking on or losing moisture. If it's losing moisture/drying out the growth rings shorten and it cups away from the pith. If it's taking on moisture the growth rings lengthen and it will cup towards the pith.

 

[Sachakins]

While your answer is good based on what the OP aside I think it is the wrong approach for the project.

Cup down will always look wrong as you get harsh transitions between the boards, rather like a saw tooth with the sharp edge facing out from the boards. Cup up results in more of a wave effect that looks less like a mistake.

Personally I would not use glue in this situation and just Use the pins.

I agree, that was my initial advice.

 

[L M Joinery]

I also agree to not use glue.

 

[Argonaut]

The boards will usually cup in the opposite direction to the picture which you originally uploaded.

It's just a sketch to indictate that cupping occurs, I took the direction of an off-cut of the T&G timber just receoved ... looking for an answer whether you fit 'radial' rings upwards or downwards.