Your questions are difficult to understand probably because you have assumed plywood is T&G and OSB is not. Both are available with T&G.

In my experience, the need for tongue and groove or edge clips is determined by the thickness of the roof sheathing and the spacing of the rafters. For 5/8" or thicker roof sheathing on 16" o.c. rafters it shouldn't be an issue. Some use clips as convenient spacers.

I don't think clips are required by code except for thin sheathing on wide spaced rafters which is something to avoid.

Actually, OSB is more stable than plywood. Reason? Plywood is layers of wood glued together in alternating directions. OSB(not chipboard or MDF) is made with pieces of wood in layers and bonded together rather than glue. In fact, an OSB made with waterproof bonding is made(costs more and is much heavier). It is excellent for subflooring.

The T&G or clips installation are more a requirement for local codes and the types of roofing to be installed. Our local building codes call for clips and a space between roofing sheathing panels because of high humidity. T&G roof sheathing can cause bulging or warping and traps humid air.

So, locally, insurance companies replace roof sheathing according to codes.

When shear and/or diaphragm construction is required, then one must evaluate ply and OSB based on their individual ratings based on thickness and construction grade, choosing one which will meet the design requirements of the project. As for normal floor, wall and roof sheathing either will work if properly chosen. I believe the greater use of OSB these days is often due to cost and availability.

I have never used OSB on roofs or as subfloor for the reasons detailed by building scientist Paul Fissette here. OSB is virtually never seen on high-end homes in our greater metropolitan area except as sheathing. A business partner of mine had the pleasure of falling two storeys through a rain soaked OSB roof once. Fortunately, the basement floor hadn't been poured and the site was clean.

JDS The T&G used on my roof is solid wood planks. Thats what im referring to. Not T&G plywood or anything else....

This entire thread would have looked completely different if you had provided that tidbit in the initial post.

sorry lol

That is a problem all of us experience. We know what we mean, but often leave out seemingly small details we do not realize are important.

In this case, the missing info was so important, leaving it out means all the info given is not applicable.

Using the new info, it is up to the insurance company and the policy as far as replacement. If the policy states replace in kind(using what was damaged) and that material is acceptable under local codes, then replacement of the original type material should be done. That means the boards will be replaced as originally installed, regardless of butt spacing or T&G type.

However, if there is no specific wording, repairs are generally done according to local building codes, with the actual selection of materials done by cost.

Another difference is material thickness. As a rule, solid wood boards were 3/4" thick. Plywood is not an actual 3/4"(or 1/2", 5/8", etc.) thick. And OSB can be thinner or thicker than the nominal thickness. That means mixing types of materials is not a good practice.

Testing has proven, using dimensional(solid) wood boards installed on the oblique to the support framing for roof sheathing or subfloor construction is the most stable and strongest material commonly used. The down side is that method is also the most expensive and labor intensive (meaning more expensive) method.

Plywood was less expensive to buy and install. And OSB was cheaper than plywood.

Then there are climate conditions. As reported in the link provided by worthy, OSB is subject to edge swelling, which can only get worse with age and exposure to moisture. There are water proof versions of OSB, they are about half to 2/3 heavier than conventional types and MUCH more expensive. To the point is is not worth using, since other less expensive materials are available.

I've seen tests where the waterproof variety sat under water for 6 months and was completely undamaged. It was, sadly, too heavy and expensive to use as subfloor material and would be way too heavy for roof sheathing.

Plywood can delaminate and solid wood swell when exposed to moisture. Once that moisture is gone, both types can return to near original dimensions and strength. Even delaminated plywood can have near new strength.

All the types of sheathing will be eventually weakened by continual exposure to water/moisture. That is why techniques to prevent moisture/water intrusion are as important as the type of material chosen.

I think this continues to reinforce the fact that homeowners are NOT over reacting when their under construction home / build materials are exposed to a lot of rain / moisture, etc and proper steps are not taken to cover / protect them. And yet... standard practices are not that conscientious.

This post proves, once again, that a little bit of information counts for a long way...!

I was engaged in a discussion on another site where someone brought up a question regarding the origins of LDS (Church of the Later Day Saints). A member of the discussion responded with an extensive treatise on LSD (Lysergic acid diethylamide) exposing his first hand knowledge on the topic. Everyone else thought it was funny.

The reason no one thought T&G referred to lumber roof sheathing is that plywood and OSB structural panel sheathing are both so far superior in stability and lateral force resistance.

Clips simply allow:

3/8" sheathing to span 24" instead of 20"

1/2" sheathing to span 32" instead of 28"

5/8" sheathing to span 40" instead of 32"

3/4" sheathing to span 48" instead of 36"

None of these options should be used for the design of a roof in any climate so clips are essentially optional panel spacers.

Plywood and OSB are superior to my solid wood boards i have?

Im getting conflicting information on this forum. lol

I'd venture to say not many folks here have ever worked on a plank sheathed roof. Most of us have experience with plywood and even OSB sheathing. My own experience comes from helping build HfH homes. Both ply and OSB were used and both had less desirable problems. Most of which came from water/moisture exposure.

I solved the deck(subfloor) moisture problem by using the donated paint(which we did not use on walls) to paint the subfloors. That effectively prevented any moisture problems until the structure could be dried in(walls/roof).

Those moisture problems continued with the trusses and roof sheathing, since they sometimes got rained on multiple times.

I worked on one house with a plank sheathed roof when the owner wanted to add a room and the best way was to restructure the roof line. The framing in the house was 2" by 4" white oak(actual 2x4) and the roof planking was 8" by 3/4"(actual dimensions)wide white oak planks.

We used 3/4" CDX plywood on 24" centers since we did not have to match the thickness as we added roofing.

I looked back at your original posts and noticed that you referred to "T&G decking". That material is a nominal 2, 3 or 4 inches thick spanning 6 to 16+ feet which is something no sheathing can do so I have to confess I don't understand your questions.