Expert: Dan Griffin - 10/15/2010

Question
Dear Mr. Griffin,

I have a pole house with parking spaces / storage underneath. I will close this area all around and install a sectional garage door.

Door width will be approx 4.2m so I purchased a second hand door really cheap and in very good condition, which is 5.4m wide. It will have to be cut, I researched all the issues to be taken into consideration. I am confident it can be done.

Question is: the existing concrete floor slopes from one post to the other by approx 150mm over the opening of 4.2m; One solution would be to cut the door to fit this slope, with one side being "smaller opening" and the other "higher". I could not find any info on the internet about something like this being done. One local garage door company quoted for a new door including a "slanted" panel for the bottom and they were not very worried about the situation, which means that it can be done, right?

I am also thinking not to cut a chase into the concrete (the local regulations are asking for 25mm rebate) but to install a threshold instead. Maybe a piece of steel angle line 30x30 with a piece of wood to the inside or possibly a piece of unistrut "upside down" (with the channel opening towards the concrete).

Any issues with this? Is it going to look extremely odd? I am aware about the inconvenience of having a threshold installed but for the last several days I drove into the garage over a piece of 4 x 2 and it is not a really huge inconvenience, you get used to it...

your opinion will be highly appreciated.

Regards,
Chris

Answer
Chris, this sounds like a hard one.  No matter what you do, it will be a visible compromise.

You've not said what the door is made of.  The concrete floor is sloping 6" in 12', that's about 1/2" per foot.  This is a substantial amount of fall.  If it is a raised panel type wood door, you will be limited by the bottom stile as to how much you can cut the door.  Cutting the door is probably not the best approach anyway, as the height of the doorway will be reduced by that amount and may become objectionable.  If this is a painted wooden door, I would consider adding a tapered wedge at the bottom.

I don't like the idea of cutting a slot in the concrete to allow the door to go down, it will only collect trash and be a nightmare.  It would also trap water and any freezing temperatures (I don't know if you have any) will destroy the concrete.  If there is no pavement outside now, you could cut the slab away the depth of the door and trim (usually about 4") and all the way top to bottom.  Pour the exterior concrete level into the recess, but this will leave a 6 to 7" jump at the high side of the doorway.

Perhaps a combination of cures would be best.  Consider raising a "threshold" condition to absorb about 1/2 of the change.  This would still be 3" which is double driving over that 2x4 and may lead to trapped water and debris inside the enclosed space.  I hope you are planning for some type of drainage to allow water out of the deepest portion of the enclosed space.  The other 1/2 could be absorbed by the slanted door bottom.  Surely this has been done by someone else in your greater neighborhood - you might drive around looking for something similar.   You could also ask the outfit that bid the door what they were planning to do at the bottom.

I would appreciate hearing what you decide.