dont we need to at least fireblock at top plate since we are framing and adding drywall. the drywall would be the concealed space? I was under impression that fireblock would stop a fire from behind wall from getting up into ceiling? but I am confused when it comes to open ceiling.

Yes, you would need to fire-block at the top plate horizontally along the perimeter of the exterior wall and vertically 10' on center. Are you doing this without permits? Because you need to submit the building department a drawing showing cross section detail.

Here is how it should be done.

yes we have submitted for permit and are awaiting it. we are planning on what you showed here but the inspecter said we need to add something to rim joists over the insulation, which is where we are confused. honestly with an open ceiling we might need something anyway to hide the insulation/roxul just sitting in the rim joists. I imagine u will see that from a distance?

do you know if the vertical fireblocking needs to be PT wood?

To hide the insulation all you have to do is install sheetrock or other material that can be painted since it will be visible. Maybe that what he wants to see there is solid blocking. That is the only thing I can think of. Ask him to clarify what he wants to see there.

As vertical fire-blocking goes, here is the code aproved materials.

R302.11.1 Fire-blocking materials. Except as provided in

Section R302.11, Item 4, fire-blocking shall consist of the

following materials.

1. Two-inch (51 mm) nominal lumber.

2. Two thicknesses of 1-inch (25.4 mm) nominal lumber

with broken lap joints.

3. One thickness of 23/32-inch (18.3 mm) wood structural

panels with joints backed by 23/32-inch (18.3

mm) wood structural panels.

4. One thickness of 3/4-inch (19.1 mm) particleboard

with joints backed by 3/4-inch (19.1 mm) particleboard.

5. One-half-inch (12.7 mm) gypsum board.

6. One-quarter-inch (6.4 mm) cement-based mill-board.

7. Batts or blankets of mineral wool or glass fiber or

other approved materials installed in such a manner

as to be securely retained in place.

8. Cellulose insulation installed as tested in accordance

with ASTM E119 or UL 263, for the specific application.

R302.11.1.1 Batts or blankets of mineral or glass

fiber. Batts or blankets of mineral or glass fiber or

other approved nonrigid materials shall be permitted

for compliance with the 10-foot (3048 mm) horizontal

fire-blocking in walls constructed using parallel rows of

studs or staggered studs.

R302.11.1.2 Unfaced fiberglass. Unfaced fiberglass

batt insulation used as fire-blocking shall fill the entire

cross section of the wall cavity to a height of not less

than 16 inches (406 mm) measured vertically. Where

piping, conduit or similar obstructions are encountered,

the insulation shall be packed tightly around the

obstruction.

thanks. I saw the list of approved fireblocking but am confused. if we need to use pt wood for bottom plate because it is in direct contact with concrete, why wouldn't we need the same thing for vertical fireblocking that is in direct contact with concrete walls? how is gypsum board an option....if there was any water exposure wouldn't it just crumble?

If you expect to have excessive moisture or water between your foundation and furred wall, PT plywood would be a way to go, in that case you should use PT for the walls as well because being in contact with masonry or not, they will have mold and they will deteriorate in no time if there is a moisture issue.

If there is a moisture issue, you have to take care of that first before you do your basement or you will have serious problems down the road having PT lumber or not.

we dont have moisture issue now, it was just not understanding why concrete floors and walls are different?

Because they're structural components, if they fail the structure will fail, not to mention it is very costly to replace them, so they want to make sure they're protected from failure and there to stay for the life of the structure.

Vertical fire-stop being this sheetrock, etc only the edge comes into contact with foundation and along the edge I always run a bead of fire rated caulk or foam, so the chance for that edge to fail are slim to none...

how would we install drywall etc at rim joists to cover insulation? toenail in some blocking between the joists in a horizontal manner to attach to? maybe easier to try and toenail in pieces of wood/osb over insulation that can be painted? that means we need to cut something to fit inside each rim joist? I cant really picture it.

and what about the wall that runs parallel to joists?

You have to install blocking and sheetrock over it so it's flush with the sheetrock on the wall and you tape the joint.

Something like this.

now I get it. thanks!!! Just found out permit was approved so we we will be starting soon!