| Author |
Message |
Liz O'Sullivan
Senior Member
Username: liz_osullivan
Post Number: 24
Registered: 10-2011
| | Posted on Monday, February 06, 2012 - 04:48 pm: |    |
I'm a bit lost on an issue. I'm working on specs for an addition/renovation. Renovation part includes existing asphalt "slab" with no vapor retarder underneath, and paint on top (existing indoor tennis court). We're designing for artificial turf (with deep infill) to be installed on top of existing asphalt. Some questions: 1. I can't find anything in the IBC that prohibits asphalt in buildings, but it seems like a questionable plan, even though it's existing. Any thoughts? 2. Do you think the asphalt (or the paint) could be acting as a vapor retarder? The paint is in good condition, so I think maybe the asphalt is acting as a vapor retarder. 3. If it's not, any thoughts on getting a vapor retarder in there, without putting a concrete topping slab on top of the asphalt? We'll need some adhesive in spots on the underside of the turf assembly, and I don't want water vapor to wreck the adhesive. But I'm not sure we want adhesive on the paint, or on the asphalt, or on a sheet vapor retarder. The project architect feels like a vapor retarder is required by code, but I'm not so sure, since we aren't putting a new concrete slab here. Sheet vapor retarders are all tested for under-concrete-slab anyway. I'm just lost here. |
Nathan Woods, CSI, CCCA, LEED AP
Senior Member
Username: nwoods
Post Number: 413
Registered: 08-2005
| | Posted on Monday, February 06, 2012 - 04:56 pm: | |
Is it an air conditioned space? The environmental controls have a significant role in the considerations of vapor drive. If you aren't doing much to affect dew point or humidity other than straight ventilation, the entire discussion may be unnecessary. |
Liz O'Sullivan
Senior Member
Username: liz_osullivan
Post Number: 25
Registered: 10-2011
| | Posted on Monday, February 06, 2012 - 05:47 pm: | |
The space is to be heated and cooled. I will find out of it has been previously. |
Mark Gilligan SE,
Senior Member
Username: mark_gilligan
Post Number: 451
Registered: 10-2007
| | Posted on Monday, February 06, 2012 - 11:34 pm: | |
In unventilated confined space I would expect new asphalt to off gas fumes from the petroleum products used in making the asphalt. This could be a concern if you have to patch some of the asphalt. You may want to consult with an expert.
If you are using the same type of paint as used on exterior tennis courts would suggest the vapor flow was not a problem. To be verified with your paint expert.
Last time I looked the vapor retarder test methods were not dependent on concrete.
Would expect that good ventilation would compensate for any vapor flow into the conditioned space. Verify your mechanical engineer will consider this.
Regarding the code issue, Section 1805 of the 2009 IBC would require dampproofing as a minimum exception “of those spaces containing other that residential and institutional where such omission is not detrimental to the building or occupancy.” I would suggest that an indoor swimming pool is a bigger problem than a tennis court. |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 156
Registered: 12-2006
| | Posted on Tuesday, February 07, 2012 - 09:52 am: | |
Considering we build vapor retarders on roof decks using asphalt and felts, my gut feeling is that you have a vapor retarder in place presuming the asphalt hasn't failed. Have you tried conducting a calcium chloride test? That should tell you whether or not you have some vapor drive.
As to Code required underslab vapor retarders, the Code references ACI who, for concrete slabs, requires a minimum 10 mil polyethylene vapor retarder. I presume that's what Liz was referring to.
Liz, if you need to somehow reinforce your existing condition before installing your turf system, you may be able to use something like a cold-process latex-asphalt emulsion product. There are some water-based products available if you don't want to use a high-solvent content indoors. It may be sticky after application.
Another option may be to torch-down a layer of mod bit roofing. I don't know how much off-gassing you would need to worry about afterwards but perhaps flushing the space would take care of that issue. |
J. Peter Jordan (Unregistered Guest)
Unregistered guest
| | Posted on Tuesday, February 07, 2012 - 11:13 am: | |
You have to verify the condition of the existing asphalt construction. Most of these are considered to be flexible paving, but over time, the ashpalt will oxidize (will take a long time for an interior installation such as yours), become rigid, and develop cracking. Because of this, I would never assume that this material would be a "permanent" material such as concrete. I am assuming that you do not have this condition, but it could develop over a long period of time. In that case, even if the asphalt could function as a vapor retarder, it would cease to do so. You might want to see if anyone knows if this was placed over a concrete slab (which might have a vapor retarder).
If there are still VOCs in the construction, these may cause bonding problems or work to degrade the turf system. This is a much more immediate problem.
You may need a topping, but not not necessarily a "full thickness" topping (think something like Ardex). This would provide an opportunity to isolate the asphalt from the artificial turf system. At this point you could think about installing any of a number of solutions; even consider a surface-applied moisture mitigation system. |
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre
Post Number: 1243
Registered: 07-2002
| | Posted on Tuesday, February 07, 2012 - 02:25 pm: | |
... and considering (as you said) that no vapor barrier exists below the asphalt now -- and assuming you're not going to magically install one below the asphalt, I think you need to treat the asphalt as the subgrade. Put a vapor barrier in there, and then treat the assembly the same way as if there were no asphalt in the first place. that might mean some topping slab; some other product to stabilize the turf, or whatever assembly the turf guy recommends. Peter said this a little better, I think. |
Mark Gilligan SE,
Senior Member
Username: mark_gilligan
Post Number: 452
Registered: 10-2007
| | Posted on Tuesday, February 07, 2012 - 05:42 pm: | |
I believe that the reference to ACI requirement for vapour barrier is ACI 302 which is not referenced in the code, thus it is not a mandatory requirement.
The trick is to step beyond rote doctrine that you always need a vapor barrier you need to ask why do you need a membrane in this condition.
Why do you need a membrane? |
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