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Rebuilding under new threshold

Joined
Jan 2, 2015
Messages
7
A previous owner of my home had converted our small 2-car garage into a second living area. He did it so poorly and the space was so awkward, that we went ahead and converted it back to a garage, and have been much happier being able to park our cars indoors for the last few months :-D

In this thread I need some help with the space directly under the new pre-hung interior/exterior door that we installed as part of the garage un-conversion. This would be the door that runs from the garage into our house. From here on I will just call this "the door".

The garage, as it was originally built, had a concrete tire stop built into it, as many garages do. Sometime later, a new divider wall was built right in front of the tire stop. For some reason the owner (at that time) chose to lay down treated 4x4 posts as the base for the new wall -- to bring it up in line with the rest of the house, I suppose. So this 4x4 base now defines the plane of division between the house and the garage. Our new door (THE door) is set into this wall.

It's a bit of a longer story involving some removal of extra homeowner-added concrete pads, but what we have NOW is a situation where the prehung door is anchored strongly into the studs on either side of it, but is not really resting on anything below. The reason things turned out this way is not important -- misunderstanding between myself and the contractor. But the point is, there is a "break" in the 4x4 post, right underneath this door. It is empty space in there, and the edges of this empty space are pretty ragged due to some concrete debris, a little decay on the edges of the 4x4s, and so on.

So the situation, basically, is that the aluminum threshold for new door has nothing under it. For the time being I have shoved in a couple of 2x6s under the threshold, and shimmed it suitably enough so that the threshold has temporary structural support.

There is also a small (~1/4") air gap between the bottom of the aluminum threshold, and the top of our in-house flooring, which drops off to the garage concrete floor, about an inch inside the threshold.

To fix this, I need to fill in this "gap" under the threshold with something strong that can be cleanly finished. I haven't done anything like this kind of work before, so I would love some suggestions. It is an irregularly-shaped space to fill, as I mentioned. My initial thought was concrete of course. But the only way to pour in concrete will be from the garage side. And the garage side will need to be closed off as part of the form work ... so I don't see that as an option.

Any other ideas would be appreciated! Thanks.


**I expect the description of my situation above is pretty hard to comprehend ... I will include some photos here later, if that's what's needed to get the point across.
 
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8man

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Oct 16, 2013
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630
Location
Bryan, Texas
I think it would be easier to re-hang the door and threshold properly and patch the sheetrock above.
 
OP
F
Joined
Jan 2, 2015
Messages
7
Thanks 8man, it may turn out you're right, but just wondering if there are other methods or mediums to consider filling in underneath.

This may help -- including some photos here:
https://goo.gl/photos/x2iRJhXAaQahF4jVA

I have shown the threshold from a couple of vantage points -- from inside the house and outside, of course. Under the threshold is the short stack of 2x6s that I mentioned earlier, with shims and a 1x board on top.

Meanwhile on either side of that short stack, you can see how ragged the underneath is. On the left side the end of the 4x4 is clearly visible -- the front is somewhat decayed or gunked up with residue from what used to be a homeowner-added concrete pad. On the right side it's a little less clear what exactly is going on. Definitely some residual concrete from that same concrete pad we removed ... also maybe seeing the front edge of that hidden tire stop.

In any case this should clarify what exactly I'm dealing with.
 
OP
F
Joined
Jan 2, 2015
Messages
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In the interest of knowing my full spread of options, perhaps I should also get some feedback on what should follow if I was to do this right, as 8man suggested. If I were to remove the prehung door entirely in order to properly rebuild the space under the threshold, what is it that should go there? Just a small pad of poured concrete, or something more particular?

Barring that option, I am considering just taking some treated 2x4s (and possibly 1x4s to finish) and milling them carefully so that when stacked, they fill in as much of that void as possible, and press up as evenly as possible against the underside of the aluminum threshold. Then I would take some form of expanding foam and aggressively fill in any gaps, to provide some additional support and stability in the nooks and crannies. Finally I might consider anchoring some kind of small stopper block, a finishing plate of some kind, on the garage-facing part of this stack -- either gluing to the floor or screwing into concrete anchors.

Thoughts on this approach? Or any others?

Thanks again.
 
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wssix99

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Mar 2, 2011
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5,162
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Chicago, IL
The thing about putting in concrete after the fact is that it shrinks and you'll be left with a small gap - no matter what. Anchoring cement will expand a little bit, but that could end up bowing the threshold. There are zero-expansion/contraction products out there by Ardex, etc. but they are $$$.

I have a similar issue under different circumstances and haven't decided what I'm going to do, yet...

In your situation, taking the door out, pouring a sill, and then re-hanging, will probably be the low cost/high quality option.
 

wssix99

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Mar 2, 2011
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5,162
Location
Chicago, IL
BTW - That curb is a gas fume curb. (Not for tires.) So, you'll want that step-up restored in to your new door.
 

DC73

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Dec 27, 2014
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1,627
Location
Lubbock TX
A brick mason could make short order of installing some concrete blocks or brick under that threshold. You could even cut some of the 4x4 away to create enough area for a lintel to span the width of the door if you want additional structural support.

DC
 

maxpower_hd

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Apr 17, 2015
Messages
2,230
Location
Massachusetts
In my area THE door is supposed to be a fire rated steel door. I had no curbing under mine due to contractor error. So I had to remove the door, pour the curbing, re-frame the opening, etc. I would remove the door and pour concrete under it. You can always shim up the bottom if it shrinks but you will end up with a flat, level surface to work from.
 
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