You start the siding on the LOWEST part of the house in a starter strip... but rarely do you start anywhere else in a starter strip. Your deck is not the lowest course of siding. And that piece will probably not be a full piece.

Use a speed square to transfer a line around the corner post. That line will represent the bottom edge of one of the full pieces of siding that is around the corner. All your rows should line up in that corner post. You also don't want to be half a row off.

Measure the height of that piece... (it's highly unlikely it will be a full piece, you almost always have to rip the first piece above a deck) so you will start it in either a finish (undersill) trim, or in a utility j. You might need to shim out the finish trim, it just depends where the profile gets ripped) You can also put a finish trim inside of a j channel, but you will want to drill a bunch of 3/8" holes in the bottom of that j channel so that water can drain out along its length... every 12" or so.

And you might save yourself a headache by putting a piece of solid pvc trim directly under your door, to fill that gap.

 

Thank you for being so thorough with your advice. I basically understood most of what you explained except for the part of the undersill trim or utility j, and finish trim. So I would be using that instead of the colored j channel I have that matches the siding ? Or am I fitting it into the regular j channel ?
Also, are you saying to put finish trim inside the regular j channel, so the ripped piece has a backing?
I'm a little confused here, this is my first time doing a vinyl siding job on my own. The worker that I had worked one day and never showed again. I'm more skilled in wood siding than vinyl. Sorry for my confusion.

 

The house wrap at the window side should be behind the flashing . the wrap below the window should be behind the flashing, the flashing in the bottom should be behind the flange.
If water stops at the upper J trim and down the sides and where, behind the wrap?

 

TamlynWrap 6.3 Installation Guide.pdf

 

The house wrap at the window side should be behind the flashing . the wrap below the window should be behind the flashing, the flashing in the bottom should be behind the flange.
If water stops at the upper J trim and down the sides and where, behind the wrap?

Oh definitely, just wasn't quite there yet in that picture. I used tyvek tape on all windows and doors. Hope this is better.

The house wrap at the window side should be behind the flashing . the wrap below the window should be behind the flashing, the flashing in the bottom should be behind the flange.
If water stops at the upper J trim and down the sides and where, behind the wrap?

Oh definitely, just wasn't quite there yet in that picture. I used tyvek tape on all windows and doors. Hope this is better.

 

Oh definitely, just wasn't quite there yet in that picture. I used tyvek tape on all windows and doors. Hope this is better.
Oh definitely, just wasn't quite there yet in that picture. I used tyvek tape on all windows and doors. Hope this is better.

Can't tell what all you did there but if you are interested this is really close to what our code is here.
How To Install a Window | Top 10 Things You Should Do! (youtube.com)

We leave the bottom open to drain because of the saying about 2 types of windows, those that leak and those that have not leaked yet.

 

Don't feel bad, we are here to help. If you start with a lengthwise rip, the ripped side should usually go inside an undersill trim. The undersill trim caps the ripped edge so it lays flat and doesn't ripple. It's the same piece you would put under a window... hence the name "undersill". (But it's also used over the top of windows, doors, on your very top row at the soffit, etc.) Whether or not you put the finish trim (another name for an undersill trim) inside a j channel is up to you. Some guys do it because undersill doesn't always lay the flattest, it can get wavy, and it just makes it look a little better / more uniform.

But depending on where your rip is, you sometimes need to put your j channel on, put a thin 1 1/2" wide rip of 1/4" fanfold foam in the j channel, then put your undersill on top of that, in order to shim the bottom edge of your siding out the right amount... so that it lays nice and level with the rest of the siding.

Another option that works well is to use a utility j, which is just like a j channel with an undersill inside it, but with a utility J you have your choice of 2 slots to put the siding in... front slot or back slot. It makes using an undersill trim unnecessary... and typically you can skip the shimming if you pick the right slot. A utility j allows you to use just one piece instead of two. All these vinyl accessory pieces come in the same color as your siding.

 

I agree that under sill (finish trim, utility trim, hare-lip) is the way to go. I would flash the intersection, use under sill, and drop in a cut down panel so it is in the same clapboard plane as the adjacent walls. I would not use j-channel. It will collect dirt and silt and will look crappy in a year or two. It will also hold water and accumulated dirt will make it stay wet while moss grows.

 

Don't feel bad, we are here to help. If you start with a lengthwise rip, the ripped side should usually go inside an undersill trim. The undersill trim caps the ripped edge so it lays flat and doesn't ripple. It's the same piece you would put under a window... hence the name "undersill". (But it's also used over the top of windows, doors, on your very top row at the soffit, etc.) Whether or not you put the finish trim (another name for an undersill trim) inside a j channel is up to you. Some guys do it because undersill doesn't always lay the flattest, it can get wavy, and it just makes it look a little better / more uniform.

But depending on where your rip is, you sometimes need to put your j channel on, put a thin 1 1/2" wide rip of 1/4" fanfold foam in the j channel, then put your undersill on top of that, in order to shim the bottom edge of your siding out the right amount... so that it lays nice and level with the rest of the siding.

Another option that works well is to use a utility j, which is just like a j channel with an undersill inside it, but with a utility J you have your choice of 2 slots to put the siding in... front slot or back slot. It makes using an undersill trim unnecessary... and typically you can skip the shimming if you pick the right slot. A utility j allows you to use just one piece instead of two. All these vinyl accessory pieces come in the same color as your siding.

Don't feel bad, we are here to help. If you start with a lengthwise rip, the ripped side should usually go inside an undersill trim. The undersill trim caps the ripped edge so it lays flat and doesn't ripple. It's the same piece you would put under a window... hence the name "undersill". (But it's also used over the top of windows, doors, on your very top row at the soffit, etc.) Whether or not you put the finish trim (another name for an undersill trim) inside a j channel is up to you. Some guys do it because undersill doesn't always lay the flattest, it can get wavy, and it just makes it look a little better / more uniform.

But depending on where your rip is, you sometimes need to put your j channel on, put a thin 1 1/2" wide rip of 1/4" fanfold foam in the j channel, then put your undersill on top of that, in order to shim the bottom edge of your siding out the right amount... so that it lays nice and level with the rest of the siding.

Another option that works well is to use a utility j, which is just like a j channel with an undersill inside it, but with a utility J you have your choice of 2 slots to put the siding in... front slot or back slot. It makes using an undersill trim unnecessary... and typically you can skip the shimming if you pick the right slot. A utility j allows you to use just one piece instead of two. All these vinyl accessory pieces come in the same color as your siding.

Hello again, I will finally be able to tackle the job this week but I have a couple of questions for you. I had bought the finish trim/undersill trim you were telling me about, but haven't been able to find the utility j in HD, but i bet the lumberyard should have it. But I'll probably just go with the finish trim inside the j channel and drill some holes. Will I be drilling holes along the total length of the of the j channel along the deck ? Or just the length under a standard patio door where the finish/undersill trim is going to give backing for the ripped piece of siding ? And if I were to get the utility j, I'm not seeing the front and back slot that you've mentioned in a picture from a website online. I've posted a picture of the finish trim that I bought from HD, and also a picture of the utility j that I found online, and would like to make sure that it's the utility j you're talking about. Thank you so much

 

Finish trim, utility trim, undersill trim... all different names for the same thing.

A utility j channel is exactly what I described. A j channel with 2 slots. Not everyone may stock it, so don't be surprised if you aren't finding it.

Yes, drill holes in the horizontal j channel above your deck if that is what you will he using.

 

Thank you for all of your help and advice. I'll let you know how I make out.