rotorhead115

Hello,
This may be a bit long. i just bought my first house and didn't notice that the converted garage into a family room did not get a proper floor. The contractor just laid sub-floor material over the garage's slab and called it good. Now I have a floor that slops to the front of the house (standard grade I think they call it) and the exposed concrete block footer is quite cold in the winter.

I like things done right and want to raise the floor above the block. This would entail hanging a ledger on 2 sides of the room and running joist the width of the room. I would also like to throw down some insulation to keep the room warmer.

My concerns are:

What size joists should I use? I was thinking 2X8's on 16's

What is the best way to attach the ledger to the block? I was thinking 1/4" X 3 1/2" Tapcons.

Using the tapcons, how many would I need?

Would pairs every 16" be enough?

Is there a particular code requirement I may need to be aware of?

Should I just contract this out?

Thanks for any advice,
Bruce

AtlanticWBConst.

This really depends on the area you are planning on working with. 2 baygarage area? single? extra area?...
Widths of floor joists are primarily determined by the span of the area they will be used in. You should use PT lumber since you are attaching to concrete.

Make sure that they are long enough. You can also use concrete lag screws.

If you are planning on pulling a permit, this may be effected by local requirements. That is the case in my area. This too is effected by the distance the joists are running off of the ledger that you are attaching to.... Either way - to play it safe: you could overkill by alternating them ^(up) and V (down) ..... every 6".

See above.

Check with your local building dept. Again, local area's requirements can vary. This would most likely fall under their guidelines for deck requirements, since the joist/floor designs are primarily the same.

Honestly, I think this is a perfect DIY project. just do your research. I strongly suggest that you sit down and draw out your structural joist design on paper....This will help you to give it fore-thought and to know exactly what you will need for lumber. If insulating the floor, I would suggest using Foam board.

(FWIW - This is actually a question for the Building and Construction section)

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Darylh

I hope this helps. 7 years ago I had to build a sub floor on a 20 x 20 concrete slab. Here is what the inspector wanted. Tar paper on concrete, 2x4 strapping 4 feet on center, 2x6 16" on center ( I needed 2x8 to match up with existing floor) , at least 5/8" t&g select ( i used 3/4") . I used a transit to find my level lines and put simns under the joists where they met the strapping. In your case the tap cons are there just to hold the outside joists against the block wall while you build the floor. I used hangers on each end to help keep the joists uprights and to prevent twisting. There was a post and beam solarium put on this and the solarium contractor was amazed that he only had to cut one post 1/8" and that was it. It passed with flying colors and in fact the inspector was amazed on how solid the floor felt.
Just thought I might mention this, hope it helps.

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AtlanticWBConst.

Good layout.

.. Only thing I would also suggest is that you could put bridging in the middle of the joists, depending on the span.
We actually prefer to use Advantech flooring, instead of T&G plywood. We feel that it is a superior product for floor sheathing that is cost comparative to normal floor sheathing.

(Question - I may be ignorant, but what the heck are you referring to as simns????)

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Darylh

(Question - I may be ignorant, but what the heck are you referring to as simns????). Oops, that was to be "shims."

Because the Joists where toe nailed every 4 feet didn't think it would be necessary and the Inspector said nothing about it that I can remember anyway.
In my project I used Fiberglass Insulation that was kept off the concrete 2 Inches with spacer blocks I made up. They where put every 16" so the Insulation would not fall and block the venting. The house had venting so I just needed to figure a way to vent this so I used a 2 inch soffitt vent at the bottom of the joist running the whole width of the floor with flashing above and then boxed in with 2x6 on the top and 2x2 at the bottom and a cedar facia. This is a vented floor not totally boxed in. I just realized its been 8 1/2 years not 7.

rotorhead115

Thanks all,
As a follow-up, this was a single car garage that spans about 9'. Should I use a vapor barrier?

I think the foam insulation will be the easiest to work with.

Does anyone know where I could research the code requirements?

How much bridging on a 9' span? I was thinking 2 per?

Will I weaken the integrity of the block with Tapcons every 6"?

The ledger is going to contact the floor at one end and be about 2" off the floor at the other. Should I place supports under the 2" side for add security?

Thanks again,
Bruce

jproffer

Maybe this isn't the way to do it in heaven, but in the real world, unless I was actually raising a floor...completely off the slab, I wouldn't worry much about a ledger. Sure ya gotta attach it to the house, but it is, after all, going to be sitting on the slab and I think tapcons in pairs every 6" is kinda overkill, but to each his own. My order of operations would be this:

- Tar paper over slab.
- Frame floor on slab.
- Raise outer end until level.
- Fill every couple feet under each joist...or...bolt 2x blocking, pushed down hard to slab, to both sides of each joist every couple feet.
- Attach to house with expansion bolts every 3 feet, staggering from top to bottom.
- Insulate as desired.
- Plywood or Advantech. (time to think about your finished floor...ceramic may need 2 layers).
- Concrete board if needed.
- Finished Floor.
- Sweep.
- Leave.

Any lumber touching concrete should be treated. Bolts going into concrete should be stainless.

AtlanticWBConst.

Ok...thanks for clearing that up, I was starting to think that you Canadians have some standard construction item (simns) that we don't know about...

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