Back entry door install

[Master Brian]

My back entry door is needing raised up about 3" to deal with poor drainage. The doorway is basically over a cement slab, so I will be pouring new cement over that to create the base. I have hung a dozen or more doors over the years, I feel 100% confident I can do this, but I will admit most have been in new construction and were pre-hung doors, so I do have a few questions.

I will be re-using my old door for now as I haven't found a new door that goes with my 1915 craftsman bungalow that I love, so I bought one of the PVC Vinyl jambs and have to cut it to fit my door. I hope the PVC is a good jamb, I went that way because the old jamb was rotting due to water damage, didn't want a repeat of this.....

So the questions are, when pouring the new concrete cap, is it a good idea to use quick setting concrete mix? I'd like to try and get as much of this done in a day as possible. I've never messed with the quick setting, so I don't know how it works and how quickly it sets up. The new base will be about 3" thick over the old slab, it will come out about 8"-10" to create a bit of a step and it will go down into the ground about 8" to provide a bit more structure to it and to help keep water from seeping under the "cap". I also plan to drop the "step" portion down about 1" to also aid in keeping any water from setting and seeping under the threshhold. I will drill and pin the "cap" to the old slab put a bit of mesh or steel in as well to help hold things together.

The jamb isn't pre-assembled and it is 36" wide, so I have to cut the jamb's header and a new threshold to fit my 32" door, that shouldn't be a big deal, but I do question if I should wait to install the threshold until the concrete cures. Or if I should try to install the jamb in the opening, then pour the concrete up to the base of the jamb and while the concrete is still wet, install the threshold and screws. Again, the threshold isn't part of the jamb and needs to be screwed down.

Anyone see a problem with this? I have included a pic to give an idea of what I'm doing, if it isn't clear. Tomorrow is supposed to be decent, so that's when I'm hoping to tackle this.
Thanks

[iminaquagmire]

I see no problem with your plan as far as the concrete work goes. Quick set is fine as long as you work fast enough. I don't think you'll need the mesh as long as you get some rebar in there and pin it to the existing slab.

As for the threshold, I'd let the concrete cure, then put your threshold in the opening. Before placing it, put a couple thick beads of silicone under the threshold and where the sides of it will meet. You can screw it down if you want using some tapcons.

[Master Brian]

I see no problem with your plan as far as the concrete work goes. Quick set is fine as long as you work fast enough. I don't think you'll need the mesh as long as you get some rebar in there and pin it to the existing slab.

As for the threshold, I'd let the concrete cure, then put your threshold in the opening. Before placing it, put a couple thick beads of silicone under the threshold and where the sides of it will meet. You can screw it down if you want using some tapcons.

Getting ready to do a bit of research on the quick set to see what working time is, but I'm starting leaning towards not needing it. Especially if I have to wait until the concrete is cured prior to setting the threshold. Is that the full 30days or just a few days to a week of curing before placing the threshold? I'll probably lightly silicone it in place after a day or so, just to stop drafts, etc.

I've been looking at several different thresholds on different houses, etc and my parents have one that is actually formed out of cement. I must admit I do like that, but wonder if I could get enough of a seal if I were to do that. I was planning on using a bottom sweap on the door and the threshold I bought has a nice rubber seal as well. Back to google I go...