Installing a Nail-Fin Window Over a Fluid-Applied WRB

in this studio mock-up we're going to be installing a pellet flange window in a wall with a fluid applied membrane the first step in this installation is going to be installing a sloped sill the reason for installing this is we want the water to migrate out if we ever do have moisture inside the wall we could do this in two ways the first way which we're gonna do here is we're gonna use a piece of cedar bevel siding the second way and rough framing we could slope this sill we'd simply just cut our Jack studs at a 5 degree bevel let's start by installing this sill to flash the opening we'll be using the joint and seam product from the same manufacturer you can see that we've already had it out it's poking through here you can kind of see where we've detailed our nail heads and all of the seams in our sheathing this product will allow us to have one membrane from the inside of the jamb all the way and out and onto the face of the WRB I'm just laying out a bead now to try to get enough that when I work it with the tool that I have good even coverage I'm not too concerned if I'm a little on the light side but I am gonna take special care to make sure that I'm completely covered I like to add an extra bead between the sub sill and our cedar sill just to make sure that I'm really making that connection now the idea is just to spread the product to cover the substrate making one membrane from inside of opening out and onto the face of the WRB this joint seam product works in conjunction with the product that we already rolled onto the wall this product just has a little more body and fiber to it and making things easier to work and connect any spots where you're a little thin you're able to just lay more product out and tool again as a good rule of thumb you want this downturn to extend beyond where the window flange will be my reasoning for going all the way to the inside of the jam I might use a little bit more material but once the windows installed it's very easy to connect my air barrier from the window jamb to the framing jamb [Music] final step before we test fit the window is we're going to use a couple pieces of our cedar shim and we're gonna place them the opposite direction of our sill that'll give us a chance to check for level across our opening we can make any finest 'men test fit our window you English (auto-generated)

here we're using a double stack of two by fours beneath the unit to protect the fin while we turn the the fin to the 90-degree orientation some flange windows will ship like this where it's integrated but folded down for shipping some will come when the 90-degree orientation some may even come completely separate in which case you'd have to set it in a bead of silicone and tap it in place now we're able to lift the window into the unit and test fit it once a carpenter on the inside gives us the ability to Center it in the opening that will ensure that we'll have even thermal and air coverage on the inside we'll also trace the nailing flange all the way around the two sides in the top and that'll give us a positive location for our bead of sealant when we set the window the final time now that we have this reference line in place we can lay down a bead of the sealant that we use to seal the rough opening we'll go both sides and the top this bead is not necessarily required by every manufacturer but it is a belt-and-suspenders approach [Music] now that we have the window tacked in place we can check for level plumb and square if we discover anything is off at this time now would be the right time to make any final adjustments before fastening the window now that we've verified the units placement and we're happy we can go ahead and fill every fastener location in this particular window but that might not be the case for your windows you need to check the manufacturer specs the final step in fastening the window will be the bottom flange but because we're using this fluid applied membrane we're also going to add a synthetic horseshoe shim which will keep this bottom flange from bonding by accident to the tackiness of our fluid applied membrane as you can see we're also using a modified truss head screw our other option would be a galvanized roofing nail now that we're fully fastened we can finalize our flashing with our sides and our Jam

In this instance our liquid applied of sealant is going to bridge from our wall to the jamb of our window and it has to go across our flange and that flange to jamb connection so I'm going to take this opportunity to mask it off just to protect the window now we're ready to apply our final bead of sealant this product is actually the fast flash product they also make a joint and seam product that's for larger gaps it's good to keep in mind that while we're working with the sealant we're just looking for continuous coverage now we're ready to move up and treat the head now that our exterior sealants applied all that's left to do is let this dry and peel our tape if at this time we were going to do a cap flashing we'd apply it in the same way that we treated this flange now that our exterior side is complete we'll move inside and manage for air and thermal

Now that our exterior is watertight we're inside and we're gonna deal with air and thermal. We're gonna do that using a spray foam application around the perimeter of the window. This method will actually apply no matter what your WRB is on the outside. Our goal here is not to completely fill the void we're just trying to fill the first inch or so from our side towards the outside. It leaves an open area on the outside of the window that if we ever have any moisture in that assembly it's able to migrate out. We're taking special care to be using the correct foam in this assembly. This is a formulation made for windows and doors which means it's not going to cause our jams to bow or bind in any way. Now that our phones installed we'll let it dry trim back any that needs to be cut away and then we have one more air ceiling detail. Now that we've given the foam a few moments to skin over we can apply a sealant over any shim that we have. That will bridge from foam across the shim and back to the foam making one continuous air seal. [Music] But those last beads is sealing in place the interior is detailed the exterior is detailed and we're confident that this is going to be a leak-free installation you.