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Community and Q&A

Tuff N’ Dri with XPS

Peter Mariano | Posted in General Questions on

My concrete contractor is telling me that I can not (voids warranty) apply 2″ XPS against the sprayed Tuff N Dri foundation walls. She is recommending using Warm N Dri. Claiming that even when dry the sprayed waterproofing membrane will degrade the XPS.
Contractor is also saying that even with taped seams the water will get behind the rigid board and cause problems. Tuff n Dri sells a product called Warm n Dri which is vaguely described as a “rigid foam board with drainage capabilities.” What if there were no Warm N Dri, the water would be contacting the membrane then? What is the difference if it has 2″ XPS against it?
Is this a case of the manufacturer dangling a carrot “warranty” in order to get you buy more of their product.
I would use UGL Drylock and apply myself but as the temps here in CT have not climbed above very cold for a couple of weeks, I think this product is ruled out. Tuff N Dri can be sprayed on in 20 degree weather.

Side Note: Great job on this site, been reading every “green,” book, magazine, conference for years. You have all the experts in one place. Keep up the good work.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Peter,
    Your contractor is correct that XPS with taped seams is not a waterproof layer for below-grade foundation walls. Water can certainly get behind the XPS.

    As to whether XPS is incompatible with Tuff-N-Dri: I'm not sure. I have placed an inquiry with a Tremco Barrier Solutions rep, and am awaiting a call back with a reply to my question.

  2. Peter Mariano | | #2

    Thank you Martin. I agree that the foam is not a waterproofed. That is what the Tuff n Dri is for. I don't see how water behind XPS or water in backfilled material, against the Tuff N Dri are any different.
    Thanks again.

  3. Riversong | | #3

    Warm-n-Dri is an Owens Corning high-density fiberglass foundation insulation/drain board that offers about R-4 per inch.

    I would not mix XPS with an asphaltic emulsion waterproofing, since it would likely be incompatible with the foam. I'm afraid you're stuck with a limited selection if you use Tuff-n-Dri or something similar - either fiberglass or rockwool.

  4. GBA Editor
    Martin Holladay | | #4

    Robert,
    I'm not certain about waterproofing systems, nor Tuf-N-Dri specifically, but I do know that XPS is compatible with most asphaltic dampproofing systems. We already established than in a previous thread on the topic:
    https://www.greenbuildingadvisor.com/community/forum/gba-pro-help/18791/how-problematic-xps-foam-board-applied-against-asphalt-based-foun

  5. Expert Member
    Michael Maines | | #5

    Peter, the rigid fiberglass board (Warm-n-dri) reduces or eliminates hydrostatic pressure against the foundation, directing ground water to footing drains. It's asphalt-based (http://www.tremcobarriersolutions.com/fileshare/MSDS/TBS370%20TNDH8%20MSDS.pdf).

    I don't see how a product can insulate if water is flowing through it but that's the concept. I would consider using a dimple membrane (Delta or similar) over the Tremco sealant on the outside, with rigid foam on the inside of the foundation wall, if that's an option for you. There are good reasons to insulate the outside of the foundation but there are also good reasons to insulate the inside.

  6. Riversong | | #6

    We already established than in a previous thread on the topic

    The Royal WE? You established nothing. You linked to an Owens Corning webpage which, while suggesting that XPS can be applied to asphaltic emulsions after curing, also specifically stated:

    "Polystyrene may be damaged by solvent base materials. This caution is not necessary with water based emulsions."

    This is hardly the kind of objective verification that's necessary to establish compatibility.

    All we can legitimately conclude from their statement is that XPS is NOT compatible with solvents, but is compatible with water-based waterproofing.

  7. Riversong | | #7

    I don't see how a product can insulate if water is flowing through it

    Well, perhaps it does so by moving all that wet coldness down to the footing drain ;-)

    Actually, I'm only half joking. By reducing the hydraulic contact with the foundation wall, it would reduce the thermal conduction into the soil.

  8. Avi Elbaz | | #8

    I'm with Michael Maines on this one, never understood how something can have water flow through it and still provide insulation. On my recent project, I did Tuff n Dri and used Delta Drain (dimpled membrane with a bonded geotextile) and insulated on the inside of the foundation. About applying XPS over Tuff n Dri, maybe you can do something along the line of Tuff n Dri, then use a thin layer of fiberglass/rockwool etc. as a separation, then apply the XPS.

  9. Riversong | | #9

    never understood how something can have water flow through it and still provide insulation

    It can't insulate only if all voids are full of water, which should never be the case unless there are no roof overhangs, no gutters, and reverse grading. Trickles of water that are directed downward will not saturate the entire insulation board, but be like a slow drip. Most of the voids, most of the time should be air-filled and hence insulative.

    Will it insulate as well as the same thickness of foam board? No. But it does double duty as both insulation and drainage mat.

    And, unless you're in termite country, it's always advantageous to insulate a thermal mass wall on the outside.

  10. Expert Member
    Michael Maines | | #10

    By reducing the hydraulic contact with the foundation wall, it would reduce the thermal conduction into the soil.

    Good point. Do you think there is any air movement within the insulation? Probably very little as it's pretty dense. Which leaves radiation as a heat transfer mechanism. Finally, a place to use that foil-faced bubble wrap....

    (I'll keep editing until I figure out this blockquote thing)

  11. Expert Member
    Michael Maines | | #11

    Trickles of water that are directed downward will not saturate the entire insulation board, but be like a slow drip.

    But that water is absorbing heat from the trapped air on its way down. I know it's all micro-scale but even a slow drip will take heat with it.

    unless you're in termite country, it's always advantageous to insulate a thermal mass wall on the outside.

    Which is now most of the northeast. It looks like they haven't crossed the MA border yet http://www.termiteinstitute.com/content/map-of-hot-zones.asp but watch out, they're on their way to get you too.

  12. Riversong | | #12

    But that water is absorbing heat from the trapped air on its way down. I know it's all micro-scale but even a slow drip will take heat with it.

    Because the specific heat, volumetric heat capacity, thermal conductivity and thermal effusivity (propensity to give up heat) for air is negligible, it will not lose significant heat to drips of water. After a certain level of surface saturation, fiberglass will lose most of its insulating capacity, but these drainage mats are supposed to have fibers oriented vertically to encourage gravity drainage rather than saturation (at least that's the theory - I've never used the stuff).

  13. Peter Mariano | | #13

    Trying to figure out what the R-value of water slowly dripping off a termites back. Robert and Michael, you guys got very technical there. I do appreciate all the discussion but it is not getting any warmer and I need to make a decision and move forward toward framing.
    Would 6 mil poly be sufficient to cover the Tuff n' Dri and then install XPS? What type of damage are we talking about occurring to the foam board, total disintegration or some slight breakdown?
    Looking into the dimple mats.
    Thanks everyone.

  14. Riversong | | #14

    Great reason for not doing a foundation this time of year. If it's only 20° out, it might take weeks for the asphalt to cure. Poly would probably protect the XPS, but how are you going to attach the poly to the wall and the XPS to the poly?

    I doubt that the Warm-n-Dri is any more expensive than XPS. Why not just stick with their system?

  15. Michael Chandler | | #15

    Would your foundation contractor allow you to drape the sprayed walls with six mil poly or the dimple mats like Michael Maines recommends and then place the XPS or warm and dry between that and your fill?

  16. Peter Mariano | | #16

    I am leaning towards the dimple mats, if I can find them somewhere. I would use the Warm N Dri but price difference is almost a $1000, without labor. For that $1000 I would like the extra layer of protection from a dimple mat plus a full R-10 from the XPS. Anyone want to come pick ax the frozen ground around the footings?

  17. Riversong | | #17

    Anyone want to come pick ax the frozen ground around the footings?

    So you're not only limiting your choices by starting a house in the winter, but risking frost heave and damage to the new foundation?

    I just don't understand why anyone would take such unnecessary risks, and also add 50% to the labor required for cold-weather building.

  18. Expert Member
    Michael Maines | | #18

    Peter, you have to be licensed to install Delta brand dimple mats but there are other brands out there. Your lumber rep should be able to help you find one.

    If you are considering applying XPS on the outside of a dimple mat, I don't think it would do much good, but I could be wrong. The dimple mats aren't cheap and, with XPS, would probably cost more than the Warm-n-dri system.

    We build houses and additions all year, every year, and understand that sometimes the calendar does not rule the schedule. There is a penalty for winter work but it's not 50%; more like 5%, 10% in a bad winter. You can rent heat blankets to thaw the ground (not the greenest choice though). If the ground is flat you might be able to lay down XPS to thaw things out but any air gaps will kill the insulating effect.

  19. Michael Chandler | | #19

    Lowes keeps Amerdrain dimple mats in the store in our area.

  20. Riversong | | #20

    We build houses and additions all year, every year, and understand that sometimes the calendar does not rule the schedule.

    In a sane world, it would and always has. Human life for millions of years - and up until just a few generations ago - was governed by the seasons. Now, because of our insatiable greed and hubris, we think we can transcend all natural limits.

    There is a penalty for winter work but it's not 50%; more like 5%, 10% in a bad winter.

    I'm not talking about whole project costs, but framing time and labor, including the additional time it takes to clear snow and ice, to protect materials and the project from snow and ice and freezing, the slower pace when wearing heavy clothing and gloves, the extra caution required to work safely (and the time lost to accidents), and the additional time and expense for plowing.

    That's a lot more than a 5%-10% penalty.

  21. GBA Editor
    Martin Holladay | | #21

    Peter,
    I am finally able to provide a definitive response from the manufacturer to your original question.

    You wrote, "My concrete contractor is telling me that I cannot (voids warranty) apply 2" XPS against the sprayed Tuff N Dri foundation walls." Your contractor is wrong.

    I just received a call back from Dr. Jim Wells, the technical director at Tremco Barrier Solutions, the manufacturer of Tuff-N-Dri. According to Wells, there is no incompatibility between Tuff-and-Dri and XPS or EPS. Once the Tuff-N-Dri coating has dried -- and that can take anywhere from 2 hours to 2 days, depending on the weather -- it's safe to put XPS directly against the Tuff-N-Dri.

    Tuff-N-Dri can be safely applied directly to foam. In fact, it is often used on the exterior of ICF walls. In these cases, the Tuff-N-Dri is applied directly to the EPS.

  22. Peter Mariano | | #22

    Thank you Martin.
    "Human life for millions of years - and up until just a few generations ago - was governed by the seasons."
    Robert, my life is governed by the seasons. I design, build, grow and harvest, organic vegetable gardens for private clients. I am aware of the added cost of building in the cold but now is the time for me to GC and build my home. I will be applying dimple mats before the XPS since we are building with a steep slope behind us and want to be assured of a dry basement, for my germination and grow room.
    Thanks again.

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