Building a floor deck
Commonly used methods
Method 1: Ledger and J-bolts installed before the pour, joists after
Method 2: Blocks installed before the pour make concrete pockets for joists
Method 3: Joists inserted directly into foam pockets before the pour
Pieter VanderWerf- Building Works
Before using any floor construction that will put the joists in direct contact with the concrete, it is important to check with your engineer or local building department before ordering materials and preparing to build an early floor. Many have concerns that the joists in contact with concrete need special measures, including:
- only pressure-treated wood for joists
- a coating to prevent rotting (for wood joists) or corrosion (for steel)
- anchors into the concrete to insure the joist ends cannot pull out
- a �fire cut� on the wall end of each joist so that, in case fire takes out the support for the other ends, they can fall out of the wall without putting undue stress on the wall
- some play around steel joists so that the constant flex of loads on them does not cause them to break from metal fatigue at the point where they enter the concrete.
Mark Hollingsworth- C&F Homes
Some companies make joist hangers that are put in place before the pour, then the concrete locks them into place. This is just like Method 2 but without the wood. These hangers have worked pretty well for me. I put a screw through the bottom to keep the hanger level during the pour. I also put rebar through the hangers to hold them securely in the concrete.
Ron Budgell - Halifax Builders Co-op Ltd.
We've used a modified version of method 1 to install ledgers - it'll take a bit more time, but I think it'll give a better job in the long term. We cut 2" pipe into 4" lengths, cut a disc out of the back of the ledger with a hole saw the same diameter as the pipe and about an inch deep and install the pipe into that hole. Tack it in place with a couple of nails, then drill for the anchor bolt through the hole saw pilot hole. Install on the block face and pour. Our objective here is to increase the bearing surface resisting vertical shear. If you add up the bearing area of all the bolts at 16"oc holding up a ledger you come up with a total pretty close to SFA with a normal installation. This method came out of a long argumentative discussion withthe engineer supervising the first substantial ICF job I did. We were both happy with it.
Pieter VanderWerf- Building Works
"Method 3" in the list of alternatives appears to have a lot going for it. Contractors who have done it usually use steel joists, but I think you could do it with wood, too. You attach the horizontal railing stud along the wall so its top is where the bottom of the floor joists should be. Then cut a pocket for the joists ( a "C" for steel joists, a rectangle for wood) and slide the joists in. They rest mostly on the rail. You may have to put vertical studs below the rail to support it--otherwise the weight of the floor above could compress the foam and skew the wall. You can true up the wall with kickers just as you normally would. Then build the rest of the floor deck and pour the wall from on top of the deck. You don't need scaffolding--just put the top blocks on from a ladder. It saves material and scaffolding, and the weight of the floor holds the wall down so you don't have to worry about lifting.