Author Topic: Questions about removing a floor  (Read 5680 times)

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Offline Abbey

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Questions about removing a floor
« on: May 01, 2013, 06:11:05 AM »
I've been toying with the idea of building a new cabin but have been seriously considering just changing my current cabin to better suit what it is I want. This would require pretty much a total gut and refinish, but since I have a structure I can change it without having to start from scratch, which I'm thinking could save me some money in the long run.

Right now my cabin is 16' x 20' with a 10' x 12' addition on the back and it's balloon framed with a loft that has 20" knee walls. The cabin is on 3 runs of cinder blocks that are on an "Alaskan Slab" foundation giving me a crawl space. The sill plates are about 6" x 6" pressure treated beams so measuring from the slab to the top of the ground floor is 39”. There is minimal plumbing and wiring, which is something I also want to fix.

What I’m thinking about doing is raising the cabin to add 2 more cinder blocks to the foundation. I would put in radiant floor tubing that would be connected to hot water tanks heated by solar panels in the summer and a wood stove in the winter. I would run the radiant floor and domestic hot water would be from the same tanks. By making the slab the ground floor I could lower the loft floor by around 50” which would then give me almost a 6’ knee wall for the second floor making the entire loft area useable.

I know I’ll have to lower all of the windows, doors, and stairs to match the new floor.

Can I simply cut the floor joists at the sill, insulate the cavities, and then install another rim joist on the inside? Will doing this compromise the stability of the wall system?

Will I need to figure out a way to hold the cabin up to remove the floor and rim joists completely and then build a new sill plate for the wall sole plate?

Any thoughts or ideas would be greatly appreciated.

Offline Don_P

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Re: Questions about removing a floor
« Reply #1 on: May 02, 2013, 03:32:43 AM »
Quote
Can I simply cut the floor joists at the sill, insulate the cavities, and then install another rim joist on the inside? Will doing this compromise the stability of the wall system?

That would create a flexible unbraced, multi hinged wall. You will at best get it down to a single unbraced hinge at the top of your block wall to frame wall. The foundation wall has been laterally braced by the framed and sheathed floor. You are proposing removing that bracing... is the wall sufficiently strong without that floor bracing to withstand vertical and wind loads without buckling?  Lifting buildings and working under that deadfall trap... go carefully, many tons wants to be on the ground. Look at everything with your bug'e eye view, that is a big boot overhead.

Offline Abbey

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Re: Questions about removing a floor
« Reply #2 on: May 02, 2013, 05:25:42 AM »
That's what I was thinking with just cutting the floor joists. I was hoping there might be a simple way to get around removing the floor joists and rim joists. When I was doing my first round of work on the cabin I had wanted to add on to the walls to give more usable floor space in the loft. The carpenter I hired to help me didn’t want to and explained pretty much the same thing as you just did regarding the floor, I would have a hinged area where the two walls connect and this would always be a weak spot in the walls. The options he gave me were out of my price range at the time and created way more work than I had time to accomplish, so I stuck with a 20” knee wall.

The cabin is very well built and I've jacked it up several times and moved it once. In fact it was originally an old hunting camp and was on pressure treated beams on the ground when I bought it almost ten years ago. I jacked it up and placed it onto solid cement blocks stacked similar to a post and pear foundation which got it up off the ground a couple of feet. After a couple of years I had enough money to have the slab poured next to the cabin and moved it about 25 feet.

From my experiences I have no doubt the cabin can easily take jacking it up again, The interior is all wood so I don't have to worry about cracking dry wall, and since I'm going to replace most, if not all, of the windows I'm not too concerned if I happened to crack one or two. Truthfully since I'm actually looking at completely gutting the entire structure I'm not at all concerned with any cosmetic damage which I might cause. I'm concerned with structural integrity after I've got it back on the cinder block foundation wall and remove what is currently the ground floor. Now it’s looking like I’ll be removing the floor joists while it’s jacked up and then rebuilding proper sills and lowering the structure so the wall sills can be attached to the foundation sill plate.

I can do all of the cinder block work from outside the structure once I’ve gotten it lifted to where I can get one or two more runs of blocks.

I believe the walls, cinder block and wood framed, are sufficiently strong enough to withstand vertical and wind loads.

Offline UK4X4

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Re: Questions about removing a floor
« Reply #3 on: May 02, 2013, 05:57:51 AM »

On your first post I did'nt understand- the last made things a little clearer, I think- see if I'm right here

So basicly you will build a brick wall to give you the height you want- all arround the cabin for example 3 ft high with the floor beneath

You would lift the cabin some how- remove the joists and edges

then lower the structure down so that the original sill plate now sits on the walls rather than the joists.

Where to lift from to me looks to be the most dificult part, as the sill plate would not be strong enough on its own to lift the structure - you may have to get creative !

if this is correct you take away the hinge effect Don mentioned- how to lift the building now becomes the main issue


Offline Abbey

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Re: Questions about removing a floor
« Reply #4 on: May 02, 2013, 07:40:38 AM »
UK,

I apologize, I should have loaded up some pictures and maybe done up some drawings to better get across what makes perfect sense in my imagination. Words can only go so far.

You’ve got it right, that's exactly what I'm talking about doing. By raising the cinder block wall another 8” to 16” I can remove the current ground floor, dropping it do the slab, and have enough room to lower the loft floor bringing the knee wall from 20" now to almost 6’ so the entire loft space is open and useable. What I want is to get the wall at least to 5' 9" which is how tall I am so that I can walk near the wall without having to tilt my head to avoid cracking it on the roof slope.

I was hoping I could do something simple like just cutting the floor joists flush with the interior wall and then putting a rim joist on the inside and covering it all up when I re-do the interior walls, but as Don_P pointed out it would create a weakness between the wood framed wall and the cinder block foundation wall. Instead of the wall being built directly on the sill plate like it should be it would have 16” on center 2” x 8” floor joist remnants the thickness of the wall.

This potential weakness was something I had been wondering about and knew someone here would either confirm my suspicions or tell me it would most likely work without too many issues.

So yeah, now what I have to do is try to figure out how I can hold the cabin up and remove the floor joists and rim joists so that I can lower the cabin back down and have the walls attached to the sill plate which will be attached to the foundation wall.

Offline flyingvan

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Re: Questions about removing a floor
« Reply #5 on: May 02, 2013, 09:45:41 AM »
  Would cutting and adding to the top of the first story walls accomplish what you want?  Adding on to the top plate sounds like a safer option
Find what you love and let it kill you.

Offline Abbey

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Re: Questions about removing a floor
« Reply #6 on: May 02, 2013, 10:15:04 AM »
flyingvan,

That’s kind of what I had planned on doing when I first bought the place. I hired a local carpenter and we put on a new roof and my thought was since I’ve got the roof down to rafters why not raise it four feet? My idea was to build a four foot wall complete with bottom and top sills and then attach this to the top of the existing wall top plate and raise the entire roof accordingly. He was talking about sister studs from the ground floor sill all the way up to the new wall height or removing the entire roof, second floor, and loft and then building a whole new second story. Like I said, what he was talking about was way more money and time, both of which I did not have then.

He said that if we did it my way the wall would always be weak where the 4 foot extension was attached to the original wall.

Now I’m in a situation where it’s not all that easy to raise a finished roof up four feet. As a result I’ve been thinking about going down because it just seems like it’ll be easier to remove a floor and lower a loft floor rather than lift a roof.

Since I’ve already got 39” from the slab to the top of the ground floor I probably don’t even need to add another run or two of blocks to increase the crawl space because adding the existing 39” to the 20” knee wall in the loft would give me a 59” knee wall, although I’ll lose some when I do the radiant floor I’m figuring I can still finish with a 50” to 55” knee wall. A little less than I’m hoping for, but way better than what I’ve been living with.

Offline Don_P

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Re: Questions about removing a floor
« Reply #7 on: May 02, 2013, 10:49:41 AM »
If you want to go up from the top, I don't see needing to sister to the ground floor, only to the second floor and extend up to desired height with a new pair of plates on that. Then reinstall the rafters and tie them in the lower third of roof height.

Going the jacking route, you can run a 2x12 around the structure attached to the studs well, a few kickers to the upper floor. Jack that and drop the floor off.

The unsupported hinge is still there between block and wall framing, with the floor rim in there you had a pair of hinges... the same foolishness as post and pier, not one hinge but hinged at both edges of the rim. You're better but not good, you're down to one hinge. The corners are good. I'd be tempted to drop a few pieces of 3" C channel through the sill into cores that are then filled, then sister the steel well to the wall studs and extend that up long, basically a few steel studs in the long field of the wall from bottom of the block to the underside of the upper floor, killing any potential for hinging.

Offline Abbey

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Re: Questions about removing a floor
« Reply #8 on: May 02, 2013, 11:22:34 AM »
It's balloon framed so there isn't a second floor, technically. I'll take some pictures tonight and post tomorrow so you all can see the loft floor and what I'm referencing.

What you're talking about is what I've been thinking. By attaching something along the walls that I can jack from it would leave the floor free for removal. As long as I add enough cross members to prevent any speading of the walls near the bottom after I take out the floor joists I should be ok. I was thinking about filling the top cinder blocks with cement and putting in some "J" bolts that I could anchor a proper sill plate to and after removing the rim joists and floor joists I can lower the cabin down and attach the wall sill to the new sill plate.

After I get some pictures you guys might have a better idea about what I'm trying to do.

Thanks for all of the help.

Offline Abbey

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Re: Questions about removing a floor
« Reply #9 on: May 03, 2013, 03:45:59 AM »
Sorry guys, I've tried over a dozen times to post pictures, and I've tried every possible combination of posting the link, I give up. Sorry, but thanks for the effort.

Offline flyingvan

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Re: Questions about removing a floor
« Reply #10 on: May 03, 2013, 04:10:21 AM »
Post pictures to Facebook or a blog, right click them, highlight 'properties', and paste that between the marks generated when you click on the little Mona Lisa portrait above
Find what you love and let it kill you.

Offline Abbey

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Re: Questions about removing a floor
« Reply #11 on: May 03, 2013, 04:31:34 AM »
I haven't given up, to tell the truth, I've posted pictures from PhotoBucket before and it worked fine, so I'm going to keep trying and maybe get some pictures loaded up. I'm a dipstick sometimes.

Offline Abbey

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Re: Questions about removing a floor
« Reply #12 on: May 03, 2013, 04:38:59 AM »
Ok, got it, I had to go back and read Mountain Don's post about inserting pictures again.

Apologies for the minor flip out earlier.

Here is a somewhat fuzzy picture showing the loft and knee wall. From the floor of the loft to the slope is 20".


Offline Abbey

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Re: Questions about removing a floor
« Reply #13 on: May 03, 2013, 04:41:07 AM »
This shows the 6" x 10" spruce beam that runs the 16' width of the cabin and the 4" x 6" hemlock cross beams. These are cut into the spruce like in timber framing.


Offline Abbey

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Re: Questions about removing a floor
« Reply #14 on: May 03, 2013, 04:42:51 AM »
This picture shows a larger section to give a better idea of how the beams all look together. I got the Waterford Stanely used, it was white enamel and I don't know why the lady stove blacked it, which is something I need to touch up this summer.


Offline Abbey

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Re: Questions about removing a floor
« Reply #15 on: May 03, 2013, 04:43:50 AM »
This again shows the beams taken from near the purple couch.


Offline Abbey

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Re: Questions about removing a floor
« Reply #16 on: May 03, 2013, 05:02:18 AM »
This gives another view of the beams. The large spruce beams are held up by a bunch of 2" x 4" rough cut studs that go to the floor so the entire beam is supported. I sistered studs on the gable end walls to hold up the hemlock beams in the same manner. This floor does not bounce at all when you're wlaking aorund in the loft.


Offline Abbey

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Re: Questions about removing a floor
« Reply #17 on: May 03, 2013, 05:08:34 AM »
If I add two more runs of blocks on the foundation wall like I'm thinking and remove the ground floor I will be able to lower the loft floor to almost the bottom of the windows. If my measurements are close to what Ill end up with the loft floor will be near the bottom of the lower window pane.

If I don't add any more blocks and use the crawl space as it is now the loft floor will be around the mid point of the top window pane.

Of course this also depends on what I do regarding the sills and joists.

Offline Don_P

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Re: Questions about removing a floor
« Reply #18 on: May 03, 2013, 09:33:53 AM »
What about cutting the kneewall off at top of upper floor, nail a 2x plate to that. Build a wall full height or one that allows you to put ceiling joists across the rafters above head height but in the lower third of roof height. This is in AK? You're greener outside than us.

Offline Abbey

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Re: Questions about removing a floor
« Reply #19 on: May 03, 2013, 10:24:32 AM »
These pictures are from last fall. I had snow on the ground up until a couple of weeks ago. Here are a few pictures of what it looked like on April 4th. There was still about 6" on the ground, some places a little more, others a little less.

When I had the carpenter helping me when I first bought the place I asked him if we could put a double sill on the tops of the studs and then build a wall extension to bring the knee wall up higher and he said it would create a weakness at the sill plates where the two walls met. He explained that the wall extension would be like a short, separate wall and would not gain any stability from the wall below. I then asked if we could cut the studs flush with the loft floor and then build a new wall from that point. He said that wouldn't work because it's balloon framed. Like I said, all he wanted to do was sister studs from the floor to the new height that I wanted which would have meant buying 16’ to 18’ 2” x 4” studs, and a lot of them.

Now I’m in the situation where I’ve got the roof all insulated with dense packed cello and I’m not too thrilled with the prospect of raising the roof around 4’ to build up the knee wall. I don’t know, maybe in the long run that is the easier way to go. Perhaps it's easier to lift a complete roof rather than holding up the entire cabin to remove the floor joists, rim joists, and then build all new sill plates for the walls.

If I just added to the top of the walls, as I had originally thought, would putting in diagonal cross braces give it enough stability?






Offline Abbey

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Re: Questions about removing a floor
« Reply #20 on: May 03, 2013, 10:26:09 AM »
Don_P,

Not AK, central VT.

Offline Don_P

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Re: Questions about removing a floor
« Reply #21 on: May 03, 2013, 05:40:11 PM »
Ahh, I had you misplaced, eastern hemlock and red spruce, I'm close to the southern end of its range, we have small stranded colonies on the highest peaks, leftover from the last ice age.
I sure think it would be easier and cheaper to pop the top than gut and lift the whole thing... even if you lose the old roof. If there is another reason for going down instead of up then that would factor into the decision.

My understanding is that the summer beam is pocketed into each eave wall. The beam is supported on built up posts as are the joists. If the upper floor diapragm (rigid horizontal plane) is firmly attached to the studs, which are sheathed to form braced wall panels (rigid vertical planes) then you have a rigid box. If you cut off the kneewalls at the top of the floor and put a plate on them, then frame and sheath a wall from that rigid base, it is not going to act any different than a platform framed house. No you cannot build a cripple wall on top of the kneewall. If you can get a small crane in, I'd set the roof off on a prepared level base of cribbing on the ground, frame and sheath the walls, and then he comes back and puts the lid on the box. From what I understand, that is how I would do it, but I'm not there seeing everything. Although my day is complete, I have seen a purple couch  :).

Offline Abbey

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Re: Questions about removing a floor
« Reply #22 on: May 04, 2013, 06:13:24 AM »
Don,

You might have gotten tripped up when I said I have an Alaskan Slab Foundation.

I doubt I could get a crane in here because of too many trees and too little money. One major reason for going down is my initial thought that this would be the simpler of the two options for increasing the useable floor space in the loft, i.e. raising the roof or making the crawl space into the first floor and lowering the loft floor.

Having considered what others have posted on this thread, as well as my continued research, it's beginning to look like the simpler option is to jack the roof, cut the wall studs flush with the loft floor, add a sill plate, build new walls to the height that I want, and then re-attach the roof.

Having lived in this cabin for almost 10 years there are several major changes I want to make to get it closer to what suits my lifestyle and needs. This can all be accomplished without removing the first floor and I can still run radiant floor tubes under the existing first floor in the crawl space so I can have toasty warm feet in the winter.

I love my purple couch.

Thanks to everybody for all of the advice.

 

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