Winter proof tape (?) for sealing gaps around windows outdoors
November 29, 2014 3:58 PM   Subscribe

I need some sort of barrier or tape that will survive the winter snow and rain to apply to the gaps between my siding and window frame.

Old house. There are gaps in the siding at the bottom of my windows that allow rain and snow to get in. The interior wall (plaster) under the windows is crumbling and allows the outside air to come in. I have "fixed" that for now. I need a fix to keep out the moisture until next spring/summer. What is the best weather proof tape on the market? I used duct tape as a quick fix and it failed miserably. If not tape, any other ideas?

Caulk is not an option (gaps too big) nor is spray foam.
posted by futz to Home & Garden (13 answers total) 3 users marked this as a favorite
Caulk IS an option because you can get "backer rod" at Lowes. You'll install the foam-like rod first, then finish with caulk.
posted by mightshould at 4:03 PM on November 29, 2014 [4 favorites]

I suspect mightyshould is right, but a pic or two might help here. Normally the window frame extends beyond wood siding, proving a small overhand that should prevent rain and snow from entering the wall even if there is a gap.
posted by jon1270 at 4:19 PM on November 29, 2014

Response by poster: Too dark to take pics but whatever siding was between the overhang and the window is gone. I will post pics tomorrow! 20 year+ old siding. Previous signs of water damage on the interior and attempted repairs by previous owners. House was built in 1900 and the original windows went almost to the floor.
posted by futz at 4:34 PM on November 29, 2014

It's not pretty (well, maybe if you're a corvid it would be) but I've found the aluminum foil tape used for high-heat duct sealing to be good in a similar situation. It has good adhesive and covers a wide gap without breaking.
posted by anadem at 5:37 PM on November 29, 2014

Agree with mightshould. The backer rod comes in various widths. You stuff the backer rod in first, then cover with removable silicone caulk, which you can then just peel off in the spring.
posted by bricoleur at 5:43 PM on November 29, 2014

Flashing tape is pretty tough stuff. Wouldn't use it anywhere I needed to remove it later, though. For that I'd do backer rod plus caulk as mentioned above.
posted by superna at 5:49 PM on November 29, 2014

Response by poster: I am going to try and take a few pics in a bit. I have the backer rod already so that may be the answer. I also have tons of caulk but not the removable kind. Will report back shortly.
posted by futz at 6:15 PM on November 29, 2014

Response by poster: Finally. Imgur was not phone friendly.
posted by futz at 7:17 PM on November 29, 2014

So it looks like you're missing the external window sill? There's supposed to be a piece at the bottom which would drain water away from the window and over the siding.

In that image, the "sub sill" extends out past the siding.

While you might be able to patch together some short-term fix using some sort of tape, caulk, or silicone, it is not likely to be a long-lasting fix. I would say that the appropriate barrier would be a new sill or sill extension, because I can't quite make out exactly what's going on there, but it does appear to be too short. A handyman with some woodworking capabilities ought to be able to fashion something appropriate, and once painted and installed, it would be a lot more durable than any tape.
posted by jgreco at 7:46 PM on November 29, 2014

Response by poster: because I can't quite make out exactly what's going on there, but it does appear to be too short.

Thank you everyone for your help! I can take better photos tomorrow if needed. The last 2 weeks have been hell. Furnace repairs, septic tank saga that has left me without h2o. Peeing in a bucket is fun!

I am broke and I need a fairly simple fix that will get me through to Spring.

- done threadsitting.
posted by futz at 8:31 PM on November 29, 2014

TBH I think the sill exists (look dead center in the first photo, and up a tad), it's just that these are home center windows that have been (DIY? probably) installed very deeply in a wall (out of code? possibly) and the siding below is insufficiently protected as a result. It may be badly rotted underneath the siding. I assume you understand that this water infiltration is what is causing the plaster inside to deteriorate.

In effect you need a sill beneath the sill (i.e. what jgreco said). I would say if this secondary sill were flashed properly it should be OK and may be able to meet code.

I would not trust any sort of tape solution to work through freezing weather. Given that you're probably going to need reconstructive surgery here I would dispense with some normal cautions and go for an emergency fix. Get a good expandable foam product like Great Stuff (get the Windows & Doors type which is less expandable and mostly won't press your window frame in damaging ways). It is an inexpensive spray can, and I cannot emphasize this enough, very sticky. Before spraying I would have a little bit of vinyl siding or flashing material cut to shape. The idea is to give it an overhang and a bit of an angle, like the window sill itself. (It looks like there may be a flippy vinyl piece there already, but it was installed in such a way that it trapped instead of releasing the runoff.) Spray, then press your ersatz temporary "sill" in place on top, and the adhesive power of the foam will hold it in place. The foam should expand sufficiently to block the majority of the moisture but you will want to try to minimize any gap at the top of this vinyl piece. This will only be enough for one winter, though; you're going to have to take your siding off and look underneath, I'm afraid.

I would check the entire exterior of the house for similar flashing/weatherproofing mistakes -- they're probably everywhere.
posted by dhartung at 11:32 PM on November 29, 2014

Best answer: dhartung has a reasonable compromise there. You would need to be mindful of sideways migration of water. Water is very sneaky and gets in any crack - especially along the sides. Great Stuff is also only water-resistant (just looked at a can) so if you follow the GS/vinyl trim route, you absolutely must use some sort of sealant. I personally love White Lightning Silicone Sealant. For your application you'd want the White Paintable (P-2032000 or similar) and not the clear stuff. The Great Stuff provides the air seal between the outside and the inside as dhartung described, the WLSS makes it watertight. I'm going to discuss fixing this with a single portion of flat vinyl trim because while there might be slightly better fixes, this is going to be something you could DIY for maybe $30 to get through the winter.

So first, it looks like a V-shaped channel of some sort already exists, possibly adhesive-backed. It may be a manufactured part of the window (a nailer strip for installation), and if so, when you remove the siding this spring and fix the damaged sheathing, you will need to have that fastened to the new sheathing. If it is an adhesive-backed add-on V-channel that someone was trying to use to fix the window, it's basically useless, as water/ice will eventually permeate the adhesive and cause the adhesive to fail. Either way, not something to mess with right now.

Cut the new vinyl trim piece to fit on the outside horizontal sill (the flat bit immediately above the V-shaped channel). Open the window first. You want to cut it very carefully to precisely fit the contours of the side frame, so that it fits neatly leaving no more than a 1/8" gap along the sides. The edge facing the house should extend at least half an inch past the exterior edge of the window sash. In other words it should have its edge wind up being underneath the lower window sash. It is effectively acting as your sill and has to guide water that runs down the window away from the house and out over the siding. It must be sloped in that direction or this will be a total failure.

Once you have your piece cut, make a nice pencil-thick bead of WLSS along the underside of the outside-facing edge and let it cure. This is intended to function as a poor man's drip edge, which helps reduce the migration of water back towards the house and the vulnerable gap in the siding. A good drip edge would be sharp as the sharp edge messes with the surface tension of the water to reduce water migration and wicking, but I see no practical way to do that easily. Still, a poor drip edge is better than none. Let the WLSS drip edge cure completely before going further.

You'd want to make sure that the underside edge facing the window has a bead of WLSS between the underside of the vinyl and the existing window sill. This should act as a glue to hold down the vinyl in the event you open the window. Set it in place and get yourself happy with the seal you've created.

Along each side of the window frame, make sure you have a nice bead of WLSS to guide the water away from the side and onto the vinyl. WLSS is definitely watertight so be sure to hit up any small gaps, etc., where you think water might migrate.

Done until spring. It should definitely last that long, but needs to be properly repaired. The Great Stuff will have left a big mess but since you've probably got to pull off the siding and the sheathing and fix the plaster anyways ...

At this point, spend some time pretending you're a drop of rain falling. Try to see if there are any more ways for water to infiltrate, being mindful that water will be running down the glass, down the sides, and down the siding of the house around the window too.
posted by jgreco at 3:25 AM on November 30, 2014 [1 favorite]

Best answer: Nashua Tape 2-1/2 in. x 60 yd. 324-A Premium Cold Weather UL Listed HVAC Foil Tape

Trades gave up on duct tape a long time ago because it doesn't last and use this instead.
posted by qsysopr at 9:38 AM on November 30, 2014 [1 favorite]

« Older Everyone's a photographer, (how) can I sell my...   |   Best Alternative to Thinkpad T440s Newer »
This thread is closed to new comments.