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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
Comments:
Pieter
VanderWerf- Building Works
Email: pvander@buildingworks.com
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
Email: hollingsworths@wbdet.com
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.
Email: mailto:reddiformn@aol.com
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
Email: pvander@buildingworks.com
"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.
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