How to measure tongue and groove width?

[Adam78]

How do i measure tongue and groove width?

Is it measured from end to end including the tongue or just the exposed/coverage area?

I need to order a piece to replace some rotted wood where the width is 90mm end to end including the tongue and thickness is 9mm. Are the online t&g widths measured in this way or is the width only the exposed area?

I can't even seem to find any merchants that have the above size?

how do i measure up to order the correct size?

 

[ray.birch]

You'll often have the nominal size (e.g. 25x150mm) which is the size before the product has been planed down.
Then the finished size, (e.g. 20x145mm).
On top of that, you may have a face size, which is the distance that each board effectively covers once the tongue has been inserted into the groove above.

Does that help?

 

[Gerrydelasel]

Are the online t&g widths measured in this way or is the width only the exposed area?

Usually it is the coverage, not including the tongue. But there's no guarantee. The building trade is basically s**t when it comes to specifications, so you have to enquire or examine everything. You're doing well when a timber/building supplier lists anything more detailed than:

Wood for sale.
Medium.

 

[big-all]

ex 4" is 88mm coverage 5" is about 112mm

 

[big-all]

they quote the width including the tongue