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Jeffrey Wilson CSI CCS (Unregistered Guest)
Unregistered guest
Posted on Friday, June 09, 2006 - 01:03 pm:   Edit PostDelete PostPrint Post

A contractor posed what seems like a good question: Should there be a sill-sealer gasket or similar separation where metal studs sit on concrete or masonry (as is typically used with wood-framed construction)?

I have never spec'd such a thing with cold-formed metal framing, and the project structural engineer also had not encountered this issue before.

Do any of you Forum participants have experience with this issue, or a suggested product that you typically specify for this condition?
Mark Gilligan SE, CSI
Senior Member
Username: markgilligan

Post Number: 84
Registered: 05-2005
Posted on Saturday, June 10, 2006 - 01:22 am:   Edit PostDelete PostPrint Post

Why is a sill-sealer used with wood walls? Once we answer this question we will likely know what to do with metal framing.
Ron Beard CCS
Senior Member
Username: rm_beard_ccs

Post Number: 133
Registered: 10-2002
Posted on Saturday, June 10, 2006 - 03:54 pm:   Edit PostDelete PostPrint Post

A sill-sealer gasket is traditionally used in wood construction, applied to the top of a concrete or block foundation wall for at least two reasons: (1) because the tops of foundation walls are generally not even, or have deviations in plane, which permit the passage of air; and (2) because of the proximity of the bottom of the sheathing to the plate which may not fully cover, or “seal off,” the junction between sheathing and plate. Wall framing, in platform framing, starts well above the junction between the plate and the bottom of the sheathing and is fully covered by the sheathing; hence, is theoretically sealed from outside air.

If the wall framing sets on a concrete slab-on-grade, either wood or metal, it should have a gasket. Further up the wall, there is appears to be no need.

Jeffrey Wilson CSI CCS (Unregistered Guest)
Unregistered guest
Posted on Saturday, June 10, 2006 - 03:14 pm:   Edit PostDelete PostPrint Post

In wood framing, I believe the use of a sill sealer is intended primarily to reduce air infiltration between wood sill members and foundation walls. Although this might also be a concern with metal framing, the question relates to isolation of the metal from contact with concrete.

Since the original posting, I found the answer to my question by referring to the current Masterspec section for cold-formed metal framing (my office master was not quite up to date). It lists closed-cell neoprene foam sealer gasket, installed to isolate the bottom track at foundation walls and slabs.
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre

Post Number: 351
Registered: 07-2002
Posted on Monday, June 12, 2006 - 12:05 pm:   Edit PostDelete PostPrint Post

and yes, I specify a sill sealer on every project, and all our stuff is metal framed. it does the same thing in metal as in wood, but its actually more useful in metal because it provides a better air/cold block.
Wayne Yancey
Senior Member
Username: wyancey

Post Number: 135
Registered: 05-2005
Posted on Monday, June 12, 2006 - 03:40 pm:   Edit PostDelete PostPrint Post

Anne's point about thermal bridging at exterior walls is right on.

In other regions I have seen 2 or 3 continuous beads of nonskinning, nonhardening, permanently flexible butyl rubber sealant; or 2 continuous strips of double sided adhesive foam sealant tape.

I detail and spec the butyl sealant or sealant tape to isolate exterior vertical steel studs against concrete or CMU and to close the gap from air infiltration/exfiltration. This technique also mitgates airborne sounds from the exterior from flanking the stud walls at openings or crevices at terminations. Acoustical sealant may also be used in these locations.


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