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yamsicle 09-24-2012 12:12 AM

New Construction - 32" Exterior Garge Door Install
I've been building a garage on weekends and am ready to install the exterior pre-hung man door. What I have done so far is frame the rough opening and then fold the house wrap from the exterior walls over the rough opening edges (not sure if that is recommended but it seemed like a good idea). I may peel that back and use blueskin or vycor underneath and than reapply the house wrap back over... tbd. Anyhow I have the following questions:

1. The door is pre-hung and I plan on installing on the concrete garage floor and seal with caulking. Not thinking about this before hand I did not account for perhaps putting a PT piece of wood underneath the threshold. I only accounted for 1/2 inch space at the top of the door. Can I install directly on the concrete? If not what is recommended?
2. I notice that from top to bottom the RO is slightly out by 1/4 of an inch (sorry I'm a DIY' er). Since the door has to be flush and plumb can I hide this imperfection by planing the back of the trim?
3. The metal threshold at the bottom of the door is hollow (about 2" x 32")and made of what looks like aluminum that juts out about 1inch. This doesn't seem very strong for people to step on. Since the door jam needs to be flush with the exterior wall can I just stick in a piece of 1x3 and trim it to the 2" width and 32" length for additional strength? And perhaps PL it to secure the wood? Any better ideas?

Not sure what to do next so any advice would be greatly appreciated. Finishing is way more difficult than framing in my mind. :(


joecaption 09-24-2012 12:24 AM

Really need to post a picture to make 100% sure the advice you get is right.

Most often the threshold is installed right on the slab with silicone caulking under it.
The rough framing should have had 1" clearance at the top and 2" larger then the width of the door. (the door not the jambs).
Under the threshold on the outside I like to use 3/4 X 6" vinyl lumber pushed up tight to the under side of the threshold as a support. If there's concrete behind it just use Tap -Con screws.
No wood of any kind added under the door.

Windows on Wash 09-24-2012 05:50 AM

You can install directly on the concrete and I see no issue with installing something in the threshold to stiffen it.

Only think I would recommend is something in the inorganic family like a PVC composite wood.

Gary in WA 09-24-2012 04:39 PM

I would use some weather-stripping foam tape at the inside edge, just behind the threshold support inside flange, add the Grace Vycor 12" up a jamb, across the width and 12" up the other jamb, covering the vinyl support edge outside and 1/4" down for water drain; Watch the folds, read the link.

Outside, you may need metal head flashing with closed ends to divert water away from the jambs where so many doors leak without them; pp. 2:

Don't use "composite" wood; wood dough (organic) and resin, it will mold when wet; WoW, BC- (before coffee)? Been there, done that...I'm still doing that, after coffee..LOL.

What type of siding? as to the door plumb...


Windows on Wash 09-24-2012 09:21 PM


I have pulled up Azek sills that have been down for years in moisture that show zero sign of moisture infiltration or mold.

You should realize that there is a PVC cap stock in most of these composite boards that shields the organic components from any moisture exposure. If you want to route or cut the boards, leave the cut side out of the water or concrete contact.

You can also use cellular PVC as there is no organic content to it.

yamsicle 09-24-2012 10:34 PM

Thanks for all the great suggestions. I will look into pan flashing at the bottom of the door since I wasn't even aware of that option. I assume I can use weather strip to create the dam and then use blueskin or whatever on the concrete floor to build the pan? Thanks for those links. Very useful. I googled until my fingers gave out and I never came across those documents. I guess my googling skills are out of practice! I've attached some images of the bottom of the exterior door and the rough opening to give you guys a picture.

I spoke to a guy at Home Depot just to see what he would say and he said for the threshold strength to just use sealing foam or rigid insulation in the hollow aluminum threshold. I seriously asked "are you sure about that?".

yamsicle 09-24-2012 10:36 PM

3 Attachment(s)
Accidentally hit send prematurely... got excited I guess... images attached. :)

yamsicle 09-24-2012 10:39 PM

To the question about the exterior wall finish I'm looking into stucco to match my house. A flatter finish of sorts. No siding unfortunately.

Gary in WA 09-25-2012 12:15 AM

WoW, I agree with PVC, but the composite could lead a DIY'er to use some decking (Trex; seen that mold, many times) in a location with water/moisture rising from a garage concrete slab (no plastic under) that could be like a big sponge, wicking water (good use of a sill-sealer under frame walls). Of course, since it's unheated, mute point anyway... I thought this was interesting; didn't know about the "Flood vents", the temp. ones have been out for many years- '80's?

Windows on Wash 09-25-2012 06:06 AM


Trex is complete crap in this application and I agree with you. Should have clarified my remarks better.

Trex mildews up on the deck for that matter.

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