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drewdin 09-10-2013 10:17 AM

Make a false floor
I wanted to open a hole in the floor, this would be a second access to the basement as when my deck was built (Before me) they placed the deck over the bulkhead.

What i wanted to do was build a 48" x 48" false floor access to the bulkhead. right now the floor joists are roughly 16" apart as they should be and the joists are 2x6.

I'm not sure where to start, im familiar enough with making a 2x8 48" rectangle box but as for any other stuff im not sure what to do.

The floor will be a 3/4" and some kind of bracing as i wanted to be able to walk on it when its down.

Any suggestions or pushes towards where to start? Thanks

bud16415 09-10-2013 12:02 PM

There are a few methods you could use. If I read correctly it’s a deck that’s over an outside bulkhead door you want access to. And you want to make a hole at that area with cover that lifts out or hinges up to access that door. And when down you can walk on it as if it was decking.

When you cut out the structure (joists) you have to replace the strength lost. One method is framing around the opening in such a way the load is carried around. The other method is add new footings and columns at the corners of the opening or where needed to carry the load. Is the deck free standing or does it connect to the house? How many joists will need to be cut? How high is the deck off the ground? What type of footings support the deck now?

nealtw 09-10-2013 06:01 PM

2x6 joists are likely overspanned already but, the standard for putting holes in structure like this is to double the full length joists on each side of the hole, a double of joist material at each end with a double hanger and the cut joist attach to that with hangers. I would build a door that locks in the straight up and down, You might want a hand rail on the inside and build a perm. ladder for going down. The trick will be stopping the door from warping.

drewdin 09-12-2013 07:47 AM

There would only be 2 joists cut, I was guessing that the door would not be on hinges but have handles that it can be pulled out if necessary. The deck is about 2-3 feet off the ground. One side is connected to the house while the other side is resting on cinderblock foundation.

Ill try to snap a few pictures later today and post them as it would help understand what I am trying to do. How would the door itself support the weight of someone walking on it? I am guessing that I would double the joists and then have the sides of the door laying on that lip alog with some type of bracing under it but i was unsure if this was enough/correct. Thanks

nealtw 09-12-2013 05:39 PM

Build the door with 2x3 for joists if the door is 4ft or shorter and line the hole with 2x3 down 2 1/2" from the top of the 2x6 joist and you will have what looks like a door jam.

drewdin 09-13-2013 11:10 AM

3 Attachment(s)
here is the room where I want the door along with the bulkhead below for reference.

nealtw 09-13-2013 05:12 PM

So where exactly would you have the door and stairs or ladder.And just so you know, that shinny thing in the center of the first photo is not a joist hanger.

drewdin 09-14-2013 02:52 PM

i wasn't planning on having any more stairs other than the ones shown. I wanted to use it as a second exit/entry only if necessary for large items and emergencies. I wanted to open right above the bulkhead.

I know its not a joist hanger, The previous owner built it and he was a complete hack.

nealtw 09-15-2013 01:33 AM

If you intend to use this as an egress, the hole must start above the nose of the step that is 80 inches below the floor joists. Then it would have to be as long as need to gain access to the top step from above. I would continue the stairs to the deck. If you are cuting 2 floor joist, I would run 2 new floor joists on each side of the hole nailed together like a beam Place temp. supports under the joists to be cut and cut the joist 3" back from what would be the ends of the hole then add a double header at each end to support the cut joists.
I would only make the opening 36" wide and add the double floor joist to each side for strength. I see you suggest 48" wide in that case you might just add one new joist along side the old ones.
Either way you want double joists on each side and a double joist, beam, or header on each end, and install the end peices with double hangers pick up the cut joist with single hanges. If the floor is a little bouncy after that you could add a post in the center of the span under the double joist as you do have a concrete floor.

drewdin 09-15-2013 06:02 PM

thanks for the info, i appreciate it.

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