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    RF (radio frequency) coax building penetration

    RF (radio frequency) coax building penetration

    New postby hwelch2171 on Fri Jul 24, 2009 10:19 pm

    The company I work for does state level law enforcement radios for Florida. At times I'm required to install a "control station". Essentially a car radio that is mounted in a metal chassis with a power supply and running a piece of coax to an antenna mounted to the outside of the building. What I'm wondering is are there specific building codes for the state of Florida dealing with wall penetrations? Currently what I've been doing is using flange with a thick rubber sleeve and insert in which is factory made to seal around the particular coax I'm using. I mount that to the exterior wall with metal concrete anchors (for block or brick walls) or wood screws (for wood walls). For sealing the flange to the wall I use a combination of vapor-wrap (a soft rubber substance similar to duct seal but won't let go) and expanding foam inside of the hole I drill through the wall. I've attempted to look on county building code websites for specific counties but I am not able to make heads or tails of the information.

    Thank you,
    Harris Welch
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    Re: RF (radio frequency) coax building penetration

    New postby Jerry Peck - Codeman on Fri Jul 24, 2009 11:49 pm

    Hi Harris,

    The only code section which would apply specifically would be the energy code for air infiltration and exfiltration and the weather resistance of the wall cladding (the brick, masonry, wood, stucco, etc.).

    The energy code is easy to address on masonry, stucco, wood, HardiePlank and similar claddings (siding) as you should be able to seal the penetration to resist air infiltration and exfiltration with a good quality sealant.

    On brick veneer, though, the air barrier is actually back inside the wall behind the brick where you cannot access it. The brick is approximately 4 inches thick, there is at least a 1 inch air space between the brick and the wall - at least that is required to be there, making the water-resistive barrier (WRB) back at least 5 inches from the face of the brick. About your only hope of sealing that would be if the rubber sleeve you are using is at least 6 inches long, coat the inboard end with sealant, slide the rubber sleeve into place, and before the outer flange its home against the brick is to seal the back of the flange where it meets the brick and push the rubber sleeve home to meet the face of the brick.

    Keep in mind that there will not be any way of knowing how well sealed the actually air barrier (vapor retarder, really) is to the rubber sleeve, but there is only one other choice (unfortunately it is a common choice) and that is to do it like the phone company, cable company, and satellite dish companies do it ... drill the holes and ignore any real attempt at sealing things back up. NOT GOOD but is unfortunately all too common for the "care less", it's-not-my-house-so-I-don't-care, installers.

    Now, with regards to leaking and weather protection of the exterior cladding, masonry, wood, HardiePlank, and similar claddings (sidings) will be the same as for the energy code and sealing to protect against air infiltration and exfiltration.

    The same problem will occur with brick veneer for weather protection too.

    Stucco on frame (masonry and stucco on masonry are the same, this is stucco on frame) creates a different headed monster as the house has the same or similar WRB as for brick veneer, except that where brick veneer has a minimum 1 inch air space where water penetrating through the brick and mortar will drain down the back face of the brick (when the brick is laid up properly), the stucco will have the WRB as that drainage plane, right up against the sheathing which is behind the WRB.

    To complicate matter even more, the stucco has a paper backed metal lath fastened over the WRB with the stucco applied directly to that paper backed metal lath. There is minimal space between the paper backing of the lath and the WRB. The paper backing on the lath serves as a bond breaker to keep the stucco from adhering to the WRB and to create that every-so-slight drainage plane.

    Here is the problem with stucco on frame: When you drill that hole through the wall you are drilling that hole through the drainage plane and have no way to seal at the drainage plane without sealing everything else up. You have just create a potential leak through the stucco on frame wall system. Again, and unfortunately, phone, cable, and satellite dish installers drill those holes and have no regard for what they are doing, slap some sealant on it and then they walk away to their next installation to repeat the same problem all over again.

    The problem comes about because water DOES GO THROUGH STUCCO, and it does drain down that drainage plane of the WRB, and you are now dealing with trying to keep that water (granted, not a lot of water, but it is there) from entering through the hole you drilled and getting behind the WRB where you do not want that water.

    There is no easy answer for drilling holes through stucco on frame. The real solution is to properly flash in a sleeve during construction of the stucco on frame wall system as that is really the only way to keep the water out.

    Masonry, stucco on masonry, wood, HardiePlank, and similar claddings should be easy to deal with.

    Vinyl siding and aluminum siding not only have similar problem with the actual drainage plane being back behind the surface you are working with but also need attention to allow for expansion and contraction movements, which you penetration and antenna lead would restrict.

    Brick veneer, you can come close.

    Stucco on frame, you just have to do your best at trying to seal it all up all the way back along the sleeve and cross your fingers the penetration does not create a problem water intrusion-wise.

    Hopefully the information above is helpful in you trying to do the penetration the right way, or at least the best way possible.
    Jerry Peck - CodeMan
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    Re: RF (radio frequency) coax building penetration

    New postby hwelch2171 on Sat Jul 25, 2009 12:09 am

    Your answer is more appreciated than you can imagine, thank you very, very much. I've been scouring over websites for codes for 2 weeks and couldn't come up with anything remotely resembling what you took the time to type out. Again, thank you very much.

    Harris Welch
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    Re: RF (radio frequency) coax building penetration

    New postby Jerry Peck - Codeman on Sat Jul 25, 2009 9:51 am

    Hi Harris,

    Glad I could be of help.
    Jerry Peck - CodeMan
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    Re: RF (radio frequency) coax building penetration

    New postby Jerry Peck - Codeman on Sat Jul 25, 2009 6:46 pm

    Hi Harris,

    1) I forgot to mention another type of cladding (siding) which you might run into, that being EIFS (Exterior Insulation Finish System).

    Those are typically installed incorrect to start with and leak before you even get there to drill a hole through the EIFS.

    There are two types of EIFS: the older, and sometimes still used, "barrier" system in which the top coating and the pain ARE THE weather resisting surface. ANY nick, cut, scratch, or hole through the SURFACE COATING IS A LEAK. Of course, though, you understand what is going to happen when you drill a hole through that barrier coating. Not good.

    The other type is Drainable EIFS in that the manufacturers have recognized the faults of the barrier system and installed a drainage plane behind the back of the foam insulation panels. Treat this as you would stucco as in both the drainage plane is behind what you are working on and you cannot get to the drainage plane to properly seal it up.

    Usually the Drainable EIFS is combined with an attempt at a barrier system coating, meaning that the primary system is drainage with a secondary system of trying to create a barrier to keep any water or moisture from getting to the drainage plane. Again, kind of like painting stucco with elastomeric paints to keep the water out, the primary weather resisting surface is the WRB installed back where you cannot get to it.

    Keep in mind that most of these systems are installed incorrectly to start with and are likely leaking to various extents due to installation errors and that drilling a hole through them only provides another passage way for water/moisture to penetrate through past the barrier coating and past the WRB drainage plane.

    You will know EIFS when you see it as when tap on the surface the entire surface sounds hollow, like tapping on a foam ice chest with a layer of stucco-like material (sometimes actually stucco) covering it. Hold a piece of wood to the inside of a foam ice chest (to act like the sheathing on the wall) and tap on the foam, it will sound similar (although not exactly the same) as EIFS will sound.

    2) Then, as I just thought of it now, you may run into an ICF structure, although there are not a lot of them around. An ICF (Insulated Concrete Form) structure is where the walls are made of foam blocks similar to concrete blocks (except they are made of foam and have plastic grids inside them holding the two faces apart and together and are used to support the steel reinforcing placed in the walls. The open center of the ICF blocks are then filled with poured concrete.

    The ICF walls will then be stucco (usually stucco is applied over the ICF on the outside), foam, 6 inches to 8 inches of solid concrete, foam, then the interior drywall. Treat those as barrier systems as the stucco and its coating is acting as a barrier for water and moisture, then you have a concrete filled foam ice chest for the walls.

    I apologize for not having thought of this previously.

    By the way, EIFS and ICF will sound about the same when tapped on.
    Jerry Peck - CodeMan
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