Looking for best way to install new brickmold.

 

Looks like you may have some bigger issues going on there with all that water damage.
The siding was installed wrong to begin with.
There should not have been j molding used at the bottom of the siding.
There's no Z molding under the siding and out over the top of the trim that's been removed.
Looks like the siding was installed without any house wrap, a big no no.
What's the distance from where the exposure line on the jamb should be to the brick?
Looks like more then the normal 2".

 

The distance is standad brick mold width. 1.5x2? Yes, no house wrap. Question is how should the replacement components be installed? Additional parts etc???

 

Joe is correct that a finish trim should have been used to start the siding... or maybe even starter trim could have been used instead the way it looks. But I can see that there *is* a z-flashing below the siding- maybe joe can't- it's white. So the problem was not caused by a lack of z-flashing... just the fact that ALL the water caught in the j-channel has to drain out the ENDS of the j-channel where it got behind the brick and brickmould, rotting it because there is no WRB. (Thanks a lot, right?) So how bad the rot is behind the brick is anyone's guess.

That being said, I'm not really sure what your question is. Best thing to use is pvc/vinyl brickmould (such as Azek) since it won't rot... screwing it on with long ceramic torx finish screws is a good way to do it. Not sure if you are asking about replacing the rotten osb sheathing or not, but that could be cut off and replaced if you wish... but you can only do the little strip between the brick and the jamb, which you would have to cut off with a sawzall or Fein Multimaster.

If you replace the osb, you would at a minimum want to cover it with housewrap, and shove a few inches behind the brick too. (Cut a strip twice as wide as you need, fold it in half over a 6" putty knife, then shove it behind the brick as far as you can... working it dow and pushing it behind the brick as you go... then cut off the excess. You could use a flashing tape but being thicker and sticky, it's impossible to tuck behind the brick very far. It also won't stick to any of that rotten crap.

Then you also would want to address the reason it leaked. If we are only talking about a little siding between the top of the door and the soffit, I'd take it down, make an end dam for your z-flashing (it's code in Canada to make an end dam, but very few in the USA have caught on to the reason why because a lot of us are slow that way... ) then throw away the j-channel and start the siding in a starter trim lIke i suspect it should have been in the first place .

 

If a starter strip is used, most likely the water will drain to the top of the brick mold and form droplets along the entire length making it basically a poratble shower and forming stains on it?? It was mentioned thatbthe z flashing should have bended end caps? Does this cause a backup water as well? Where would the water go? Should the j channel remail and drill some drain holes near the ends?
I understand that i need to cut out the rot and wrap with tape or vaopr barrier. I intend on using pvc molding and jambs.

 

First I would remove and replace all the rotted OSB on the sides, remove the siding up at least a couple of rows to check for more damage.
As mentioned depending on how much siding it above that area I might even take it all off so I could add the needed house wrap.
Since I own a brake I always trim out my garage doors with coil stock if there's already wooden jambs in place.
Idealy the jamb gets wrapped before the door seal goes on so the it covers up the exposed end toward the door.
Sides get wrapped first, then the top piece.
The metal should be bent so it extends right over the sides and behind the brick and at least 6" up the wall over the door, the house wrap is laid over the coil stock at the top of the door.
Now you have a water proof layer to install the trim over and all the exposed wood would be covered on the jambs.
Sounds complicated but to anyone that knows how to use a brake and a pair of seamer's it's a simple job that should only take a little over an hour.
Any real siding company could do it for you.

 

I would remove the siding, replace rotten osb, and install wrb behind it. No more stains. The stains are coming from the wet rotten wood. Once WRB is installed, the water will stay clean. Starter strip is what should have been used, not j-channel. Water should drip from the top of the drip edge (z-flashing) freely. As a side note, there should NEVER be any caulk between the top of the drip edge and the siding... it has to drain.

The end dam on the flashing forces water to drain out the FRONT like it should... preventing it from going behind the brick at the ends.

Holes in the j-channel might help a little, but when the j-channel is pressed up against the z-flashing there isnt much room and the sheer volume of water means they would not be enough to stop the problem. Unless this is changed, your whole wall will eventually be rotten. You won't be happy if the studs supporting your garage header rot.

 

Do not use drain holes in the J molding!
The J needs to go.
All the dirt what washes down the siding will be funneled out the holes and will stain anything below the hole.