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Waterproof Windows with HydroGap

Some people (mostly folks who live in big cities!) think that builders who live in small towns are behind the curve when it comes to technology and better building practices. But the truth is that every state in the U.S. is actively improving building codes, and through new requirements on everything from decks to framing to air infiltration to housewrap, even small towns in America are getting up to speed.

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(Note: Click any image to enlarge)

Here in Oregon we have a unique code requirement when it comes to housewrap. Officials in our state have recognized what everyone has known for years—sandwiching plastic housewrap tightly between OSB sheathing and siding is a recipe for disaster!

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Just think of all the nails you drive through the siding and all the holes they make in the housewrap. If housewrap doesn’t shed water pretty quickly, all those nail holes are pathways for water to reach the sheathing.

Because of pressure differentials—like high-pressure wind blowing rain against the siding—moisture will always penetrate siding and be drawn toward areas where there is lower pressure, like the housewrap behind the siding. That’s why siding is called the “PRIMARY weather barrier.

And most of the siding products we use, like wood, fiber cement, and OSB, absorb moisture, and sometimes a lot of moisture. That’s why they’re called reservoir claddings. Without a gap of some kind to help that moisture dry out (building scientists call that process diffusion), that moisture works its way through the housewrap, into the sheathing, and…well, you all know that story.

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Rainscreen walls and drainable housewraps—called “drain wraps”—help prevent moisture from penetrating the housewrap.

In Oregon, we now have a new code requirement for housewrap—a 75% drainage rate requirement. Now I don’t know what the percentages really mean, but I do know that a drainage rate is a measure of how quickly a specific housewrap drains.

To meet this new code requirement, we’re starting to see new drain wrap products even in my little town in Southern Oregon. Recently, I installed some HydroGap. Because of the five-foot tall rolls, I found it easier to install than the other wraps I’ve used in the past. And hey, if it helps the trim and siding last longer on my jobs and keeps the wall cavities of my customers’ homes dry, I’m all over it.

Comments/Discussion

25 Responses to “Waterproof Windows with HydroGap”

  1. Ray Menard

    The evolution of window and door installation continues. I like the HydroGap concept – seems logical to me.

    The one ongoing question I have when watching these window/door installs with the various wraps and tapes though is why wrap the house wrap back into the building at the sides of the opening? Just seems wrong. If water manages to get that far won’t it just follow the wrap (wether behind it or on the surface) into the building?

    Seems to me that cutting the sides flush and then installing the window/door with caulk behind the nailing flange followed by the tape is a better technique. Maybe even better would be to cut the house wrap 1″ to 2″ or so away from the opening then tape to the wrap and sub sheathing and then tape again after the caused window is installed.

    Just asking – I don’t really have any data to back me up.
    I always appreciate you folks who take the time and care to post these how to articles. Thanks Scott.

    Reply
    • Paul

      I’ve puzzled over the same question from time to time and have seen it both ways. But as usual there are best practices given the different configurations and combinations of door/window frames and house wraps. Scott demonstrates what I would consider the Best Practice for this type of window frame. When we use to use felts we often simply cut them flush with the end of the sheeting at the opening. Then as often happens and we adopted a new Best Practice, we started rapping around the trimmers and cutting the felts flush with the drywall similar to the way the Scott demonstrates in the video. Although house raps have many many benefits over traditional asphalt impregnated felts I do like the flexibility of working with 36″ course width. This comes in handy around all openings. And is particularly advantageous when it comes to counter flashing at the head. In this respect Scott is dead on. The detail at the head of the opening is critical. But using the multi-course methods required with traditional width building papers was almost fool proof. You were always able to apply a continuous length across the top of the opening. Although the “adhesive” technology of the new self stick flashing’s and tapes seems permanent, if it does fail some day, you have a diagonal slash in the water barrier above an opening! But it seems to me that as long as you are using an adhesive gasket like approach (as shown in the video) and not mechanically weaving courses, the adhesive window flashing seals the edge of the opening regardless of whether there is house wrap folded around the trimmer. And I would argue that if done properly you could eliminate the trimmer wrapping with the house wrap. But what’s the benefit in eliminating that, a couple of cuts with your knife? Not a lot of time saved there. Another detail that I liked that Scott employs is the added counter flashing affect of applying caulking on the inside of the nailing fin of the window frames. Belt and suspenders yes but I like the approach. Of course this is lost if you are installing traditional doors where there is no nailing fin and now what do you do? I was once on a job at a local University dorm project that was wood framed. The engineers required us to take the extra precaution of “kerfing in” copper side flashing around openings that were then woven into the building paper and sealed with butyl caulking. There were also three layers of counter flashed rubber window flashing woven around the openings. When I asked one of the young architects about this detail he replied that it may have seemed like over kill but they were trying to construct a wood frame building that was capable of surviving 75 years, a requirement from the University. It seems they too were concerned with this aspect of sealing the sides of the opens.

      Reply
      • Scott Wells

        Paul,
        Let’s hope that all of the self adhesive flashings last a long time, or an awful lot of us will be in trouble. I find myself using them more and more all the time. As far as flashing for doors, I’ve used peel and stick flashings quite a bit. I install the building paper in the same fashion as a window opening, and then install the door. Then, I tape the paper and onto the jamb (covering about 1/2″ to 3/4″ of the edge of the jamb) making sure not to leave tape exposed where it will be seen after my trim is installed. I feel like this gives me a good chance to keep water out…..as long as the peel and stick flashing doesn’t break down!!
        Scott

        Reply
  2. Steve

    I can see how this housewrap will allow liquid moisture to drain a bit better than other housewraps. However, there will still be many hundreds of holes punched through the wrap when the siding is placed. This seems to still reinforce the argument of air leakage bringing in moisture behind the wrap to the sheathing surface. I don’t really know. As in the previous comment I have no data to support this idea.

    Reply
  3. Greg

    I can understand what both are saying and have read different articles where carpenter/writers of articles were installing just as described in comment 1. As to the issue of moist air, it seems the new housewrap being used at least by some is the kind that sticks to the sheathing. I don’t have any brand names but I read it originated in Europe. I too continue to monitor this system of air and water barrier prevention, as it appears there are many different ways to do this. Which is correct or better, I have no idea, but I to like to terminate a few inches from window openings and tape against structure as Ray had mentioned. Then over window and over taped housewrap. I have not used the sticky housewrap, but may be awful hard to put on.

    Wish someone who is more technical or has investigated this would chime in here on this.

    Reply
  4. jkirk

    i like the idea of the housewrap product but does it provide enough drainage for all types of siding on the west coast. locally all wood and fibre cement siding has to have atleast 1/2″ air space via rain screen between the back of the siding and the face of the house wrap. here on the east coast its a high humidity, high wind zone with a brutal freeze thaw cycle in the winters

    Reply
    • Scott Wells

      jkirk,
      Here on the west coast (specifically west of the Cascades and Sierras) we have a pretty mild climate. Rain is our biggest issue. I would be comfortable using this product behind fiber cement siding and wood composite/plywood sidings. The Hydro gap spacers provide a 1 mm gap. If your local building code requires a 1/2″ gap, you may have to use something different.
      Scott

      Reply
  5. Sonny Wiehe

    Scott,
    If you skip tape the hydro gap material that laps over the window head flashing, then why don’t you skip tape the hydro gap material that laps itself (i.e. the pieces you ran at the rake angle of gable ends)? Is there a different moisture drainage principle at work between shingle lapping at a window element vs. the material itself?

    Reply
    • Gary Katz

      Sonny,
      There’s actually a major difference between the two ‘laps’. In the case of the window, the window flange is sealed with adhesive flashing to the sheathing. Any water that gets behind the housewrap above the window, and runs down the sheathing, will be directed out above the window–after all, you have to seal the nailing flange on the window or moisture will penetrate the opening, especially on the head jamb. Where the housewrap laps over itself, the lower layer is not flashed to the sheathing; there’s no means for water to be directed back out from behind the housewrap; there’s no reason to skip tape the housewrap. In fact, the manufacturer doesn’t even require tape on lap joints.
      Gary

      Reply
      • Sonny Wiehe

        Gary,
        Thanks for pointing out that difference However, using your logic, I don’t see any reason to illustrate skip taping the hydro gap at the window head; particularly if you’re not going to do it at shingle lapped house wrap joints .

        IMO, if we’re talking about “best practices” of house wrap installation (whether it’s hydro gap or some other manufacturer) then skip taping at window heads and then continuous taping (like Scott is doing) at shingle lapped joints confuses the issue of moisture management. If your intention is to best manage bulk moisture penetration at any point above the window, then logic should dictate that any primary sheet of shingle lapped house wrap should theoretically be seamed taped (red code in the sketch) to the sheathing. This will allow an bulk moisture to be evacuated as soon as possible after a leak or diffusion. Any overlapping sheet areas should either be skipped taped (as temporary wind lift measure if that is your concern) or simply stapled like the rest of it.

        Personally I feel that focusing on skip taping house wrap belies the fact that house wrap is going to have so many points of potential bulk water penetration (i.e. siding) that this detail really doesn’t matter. And if it does matter to someone (like at a window), then why doesn’t it at all other points of an exterior wall as well?

        Reply
        • Gary Katz

          Sonny,
          I’m sorry you’re confused. I don’t believe anyone else is? The skip tape is merely there to hold down the edge of the flap–which might be a problem on a long window, not a short window. You don’t need it anymore than you need the seam tape. As I said, the manufacturer doesn’t believe the seams need to be taped. If you read the article, you’ll see that Benjamin Obdyke doesn’t believe that housewrap is a Weather Resistive Barrier. It’s a Water Resistive Barrier. Yes, as someone else commented, all those hole poked through housewrap from trim and siding nails make it almost impossible to seal against wind/air movement. I think there are bigger and far more important issues than picking apart the seam tape–issues that Scott covered nicely and other builders value learning about. The seam tape really has no bearing on anything. I remember my father once said: “Anyone can come on one of my jobsites and pick it apart, and I can go on their jobsite and pick it apart, too. But where’s the value in that? It takes a lot more courage to share your own failures than the failures of other builders.”
          Gary

          Reply
  6. John K

    I’m in awe of all these wrap technologies. I used to live in a house that was at least 100 years old in North East Ohio. Moderate temps and fair amount of humidity. It had tar paper wrap. Wood shingle siding with stain-turpentine mix. Inside walls were lath n plaster. I remember my mom telling me to cut an opening in the wall for a thru-walkway. It was dry as a bone. If air ever gets trapped with these new wraps then the time to dry out takes exponentially longer, I would think. I never saw any mold or mildew problems either. So what has changed? Could it be the lumber? LoL Thanks for the video and your expert demo.

    Reply
    • Ray Menard

      What has changed ? – Plywood sheathing, real insulation, drywall sheets rather than lath and plaster, paint coatings, etc., in other words lots of surfaces covered better than with boards and the inevitable resulting gaps which in your 100 year old house example, used to allow outdoor air and interior moisture to freely migrate through walls back and forth in a natural cycle that promoted drying.

      You are right – “If air ever gets trapped with these new wraps then the time to dry out takes exponentially longer,…” If we weren’t concerned with conserving heat and cooling we could build just as in the past and have nice dry constructions although very very energy inefficient buildings, impossibly expensive to heat or cool. This is why we are all asking how best to do this house wrap/caulking thing. Badly done it can create very destructive conditions in short order.

      Reply
    • Scott Wells

      Thanks, John. I think what has changed is our energy costs. Those old houses definitely “breathed.” And if they are still breathing – they are exhaling dollars. I try to “tighten up” air leaks and potential water leaks on every project I touch because of what you pointed out. If wall cavities get wet, they could take a long time to dry out. Like you, I want to keep my building components from ever getting wet.
      Scott

      Reply
  7. Greg Callow

    Thanks for introducing this product to us Scott. I like the idea of installing the air gap with the house wrap. Currently we are installing rain screens with 3/4″ furring strips that takes way too long. And for board and batten cement siding, I can see this being a perfect match.

    I think there are a number of different ways to detail penetrations in housewraps that will work. I don’t wrap my house wrap into my opening either. Mainly because I found it to interfere with the foam gun. Also, I quit caulking window flanges. Between the tape over the nailing flanges and the foam on the inside, caulk became unnecessary. And inevitably it finds its way onto the installers fingers and finished interior.

    I appreciate the cant strip you installed onto sill. It’s not a detail I’ve seen anyone do before.

    Reply
    • Scott Wells

      Thanks, Greg. I certainly did not invent the sill pan cant strip. I sure do like that detail, though. I use it whenever I can for window and door openings.
      Scott

      Reply
  8. noah keith-hardy

    I’ve tried a self adhesive wrap from Grace called enVs. Pricy, but not at all difficult to install, even working solo. It has an embossed surface that their salesman said met the BOCA standard for a draiage plane. I haven’t researched it for myself, but it has to be a whole lot better than using ice and water shield here on the coast where the wind will drive moisture through vycor or tyvek.

    Reply
    • Scott Wells

      Noah,
      Sounds good. Is the Grace product self-healing? (Does it seal up around all of the fastener holes that penetrate it?)

      Scott

      Reply
  9. Andy

    This is the best waterproofing installation video that I have ever seen online. Thanks for the watch!

    Andy

    Reply
  10. stuart robertson

    Here in NZ,where our standards are largely based on Australian and American building codes, house wrap is virtually compulsory.
    In fact, some are made in the U.S. Flashing tapes at openings are also required.These are both secondary barriers.The wrap also acts as a required wind/air barrier or in higher wind zones a rigid wind barrier is required;commonly CCA or LOSP treated ply or an Eterpan type sheet >then wrap over that.
    In some instances,dependent on exterior cladding type,direct fixing of cladding may be acceptable,however the bulk of ALL claddings,in order to adhere to code, must be applied to a vertically fixed batten(nominally 20mm,3/4″)thus forming a vented cavity cavity.There are numerous flashing systems to suit this set up and varieties of batten (eg;Cavibats).Typically though these are gauged CCA treated 2×1.
    Once you incorporate this into your planning and process it is fairly straight forward.

    Reply
    • Scott Wells

      Stuart,
      I think it’s so cool that we can share ideas even though we’re in different countries thousands of miles away! The system that you’re describing happens here in Oregon, as well, and I do like the idea of an open cavity for moisture to escape. I, personally, have never installed one like that. Do all of your jambs for your doors and windows have to widen to accommodate that extra thickness? How do you keep big bugs from crawling in at the bottom of the open cavities?
      Thanks for your comment.
      Scott Wells

      Reply
  11. Kimber Janney

    Dow and Owens Corning have systems- rigid foam with taped joints to act as moisture barrier and continuous insulation in one package. Seems like moisture could get trapped somewhere. Would it be good to put a drainage plane on top of the foam or below it?benjaminobdyke.com recommends both. Has anyone had problems with exterior foam over OSB? We put 1″ foam over 2×6 walls with fiberglass in the cavities for an economical but high performance assembly. Our Climate in Colorado is forgiving when it comes to moisture but we can still have moisture issues.

    Reply

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