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nutlog 11-06-2009 05:24 PM

Large metal "tabs" in openings cut in bi-level rim joist... What are they? Insulate?
While replacing the drop ceiling in my bi-level, I noticed openings cut into the rim joist... I see rounded metal "tabs" sticking through, what appears to be the back of our aluminum siding, and can feel lots of cold air around them. Pictures below.

The rim joists currently have no insulation. And our basement gets damn cold in the winter; could these openings be the main culprit? Should I 1) insulate fully, using thick, rigid foam blocks around the whole basement ceiling? 2) Regardless of that, at least fill in these openings with spray foam?

Of note is that we do have a gas furnace, dryer, and water heater all downstairs (utility room is one room away from the family room where I see these rim joist openings)... I read that if we seal "too" well it could cause airflow/combustion issues. Any concern there?

I just don't know enough about construction to know exactly what these openings and metal tabs are for (what are they?), and I'm sure one of you can look at the pics and know immediately what I'm talking about. :) Any advice would be much appreciated. Thanks!

Scuba_Dave 11-07-2009 04:28 PM

Do they appear strong enough to have listed part of the house into place?
Wondering of the house was built off-site in pieces & then trucked there & lifted into place

nap 11-07-2009 04:36 PM


Originally Posted by Scuba_Dave (Post 350280)
Do they appear strong enough to have listed part of the house into place?
Wondering of the house was built off-site in pieces & then trucked there & lifted into place


panelized basement walls. They are set in place with a crane or large lift of some sort.

SULTINI 11-07-2009 05:23 PM

Maybe the house is a Modular house and the openings are where the slings were placed and removed after setting the unit on the foundation.

Just a guess I have seen this process several times.

RobQuillin 11-07-2009 07:42 PM

My guess is panalized basement walls. It looks to me that the builder wasn't able to remove the crane loops so he bent them down and notched the floor rim to bury it in the wall. I personally would have just cut them off, but it looks like that wasn't something that he wanted to do. I would just cut some extruded foam and fill the hole and then insulate the rim. I would say to just use great stuff but it might push your siding out.

As far as it being unsafe to insulate the rim, that is more of a concern if the house is very air tight. Judging by the photos, I am pretty sure that you don't have a house that is too air tight. I would just make sure that the exhaust pipes for your funace and hot water heater are in good condition and then try to seal up the rim of your house. :thumbsup:

SULTINI 11-08-2009 07:53 AM

NAP Not here to dispute you however as my post states I have seen many modulars lifted this way.

Yes they arrive on site on a metal framed trailer ready for pick up.

There are large slings with spreader bars that run under the bottom plate cutouts, when the half of house is lifted the crane is lowered and the slings are removed and the 2x6 (yes 2x6) pieces of bottom plate are placed back.

Then the other half is placed and pulled together with binders.

Then all the other stages are completed.

Now I am not disagreeing the issues of cast placement I am just giving Modular information.

I actually think they are for lifting cast because Modular cutouts would be neat and almost perfect the cuts in the picture appear to be sloppy.

tpolk 11-08-2009 02:32 PM

please check with your gas company to make sure you have adequate air for gas appliances after you insolate. flame will seek out air if it is not at burner

Maintenance 6 11-09-2009 07:01 AM

To the OP, I would get a can of low expansion foam and fill those voids. That will stop the air infiltration.

nutlog 11-09-2009 03:13 PM

Thanks for the replies. I had already picked up a can of Great Stuff, but hadn't thought about the possibility of it expanding and pushing the siding out. I'll go exchange it for the door/window stuff, which doesn't expand.

Lack of airflow is not a problem, at least right now... the ground level of the house (not a basement; the lower level is fully above ground) is still a good 10-15 degrees colder than upstairs. It's really poorly insulated, air leaks around doors, and of course these big holes in the rim we just found. So as long as it's safe to insulate the rim, I'll stick some 2" rigid foam around, on top of those spray foamed holes.

For reference, when insulating the rim, do I need to just do the 2 opposing sides (small blocks where all the joists meet the rim)? Or also the wall perpendicular to those, which is also an outside wall, that runs parallel to the joists (with a long rectangle block)? Thanks!

Maintenance 6 11-09-2009 03:19 PM

Do everything that has an outside exposure. If you cut your rigid stuff ahead of time, you can use the low ex stuff as an adhesive to keep it in place.

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