wire mesh codes

radmix

I just looked at a project with approximately 5000 sq ft of slab radiant.  I was informed that there will not be wire mesh in the slab due to the code that states the wire mesh had to be grounded because of interference with communication wiring in house. They will be using fiber concrete instead. The problem is that all of the tubing has to be stapled down to the insulation increasing the labor on the project. Has anyone else ran into this?

Jamie Hall

I haven't seen this

as a code issue, but it is certainly an issue with regard to any radio electronics, such as wi-fi, wireless telephones, and like contraptions.  The same thing applies to wire mesh type lath for plaster -- not that that's common anymore.  Both wire mesh floor reinforcement and the lath will reduce the range of things like wi-fi drastically -- in some cases, prevent transmission or reception beyond one room completely.

Tim P._3

building code?

I don't know of any building code that dictates this.  Perhaps there is a TIA/EIA standard that says you shouldn't use steel in buildings intended for certain uses.



Why not just bond the mats.  If they are tied together with tie wire you would just have to bond them to the GES (unless the standard they are following dictates otherwise).



I doubt this is something enforced by the building department; more likely the designer.

Jamie Hall

Trouble is...

what you are making with the mats is what is known, technically, as a "Faraday Cage"; the effectiveness of the cage is related to the wavelength of the radio emissions in use and the dimensions of the cage.  Unfortunately, most wire mesh reinforcing has dimensions which are astonishingly well suited to shielding against most of the radio frequencies used in homes today.  This is wonderful if that is what you are trying to do -- such as keeping your wi-fi or 'phone from being eavesdropped -- but not so great if you really want to use it around the place.



Worse yet, the better it is bonded or grounded, the more effective it is... as a shield.



I might note, as a sort of aside, that wire mesh is used for exactly this purpose in some high-security installations!



As I said earlier, I don't think this is in a code anywhere, but if there is a concern about possible use of wireless devices in a structure, it is better to avoid wire mesh.  Fibre reinforcement doesn't have the same problem at all, and is recommended.

radmix

Codes

I spoke with the GC today and it turns out that this is a code in NY. All of the re-bar in the slab and walls need to be grounded as well.

martin

Tubing without mesh

If you have foam board down, hopefully styrofoam get yourself one of those tubing staplers for foamboard. They work slick and the tubing goes down fast and secure, and you can do it from and upright position a matter of some concern to some of us

Tim P._3

NY or NYC?

If this is outside of NYC, I'd like to know that code section.



I guess it doesn't matter either way; if that's what they want, that's what you gotta give them.