# Forum Home Renovation Doors, Windows, Architraves & Skirts  Window flashing - sarking & weatherboards

## ChocDog

I’ve looked around a fair bit and there doesn’t seem to be a consistent approach to flashing a window opening. Specifically for the following setup: 
1.       Stud frame
2.       Sarking applied
3.       no cladding currently on frame
4.       Weatherboards (standard round edge overlapping type) to be installed post window install
5.       Timber window & frames
6.       External arcs to installed on face of reveals (nominal reveal depth: 130mm = 10mm PB+90mm stud+30mm for WB overlap)
7.       Low expansion polyurethane foam to be used post window install for draught proofing
8.       N1 wind rating (Melbourne) 
I have no problems understand the head flashing process (ie aluminium flashing under head weatherboard and over top of head external arc):     
But it’s the sill and jamb flashing I’d like clarification on. 
I’ve looked though the guides by the AWA (Aus Window Association), different window manufactures, etc but they don’t provide a holistic approach to the above. It seems simple, just think about how to water getting in!, but its always good to get some experienced advice. 
I like the approach the Yanks use with aluminium backed butyl flashing tape ala http://https://www.youtube.com/watch?v=ycdgjUZf0H0 yet its not completely relevant to Oz cause most of their builds are ply clad over the stud frame and their windows are fully flanged.   
Personally, recommendations like the below from both the AWA and a specific manufacturer to use aluminium flashing directly below the sill fashioned into a pan don’t seem right to me. If its hard against the bottom of the window frame, then the frame itself will absorb the moisture, and ideally, there should be a fall in it so that the water drains away.    
My plan, unless people recommend something else, is to:
1.       Cut sarking in an X shape across window opening (fold back and trim to half stud width to allow adhesion surface for #2)
2.       Apply butyl flashing tape to bottom sill and head as per this guide: http://www.thermakraft.co.nz/sites/d...4PP%20LR_0.pdf 
3.       Apply packers to bottom sill to (1) achieve level; (2) provide gap b/w window frame sill so that if water does pool, window frame is not sitting in it
4.       Install window (reveal pre-primed)
5.       Apply Low expansion polyurethane foam around perimeter for draft proofing
6.       Install cladding
7.       Install external arcs on face of reveal (ie over WBs)
8.       Fill gaps b/w arcs and WB’s with sealant
9.       Install aluminium  head flashing to cover to arc  
Opinions? 
(BTW, Ourbuild, you should do some vid’s on window flashing applications for Oz. I know you’ll get at least one viewer…)

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## SilentButDeadly

We did it like the AWA seems to suggest with folded metal flashings.  Start from the sill flashing then install window unit then jamb flash and finally head flash.  Assuming building is already fully wrapped of course...and I might've skipped the steel sill flashing and used plastic dampcourse...

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## OBBob

I've got an Alan Stains book ... better not go there again ...  :Doh:

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## r3nov8or

You don't mention a metal flashing for the bottom. I can't see how the Watergate/Bulldog method achieves this.  
Also, I assume re your point 9 that you will install this under the first weatherboard above the top arc. Easier to install this before you add that board.

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## ChocDog

Thanks SBD for the info. 
Bob, !!! His books are good, just lack some detail. A bit hard to cover it all in a book of that size.

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## ChocDog

> You don't mention a metal flashing for the bottom. I can't see how the Watergate/Bulldog method achieves this.

  
The complete face of the bottom sill (ie 90mm), and 200mm up the jamb studs is covered by the butyl tape. This is then folded down to cover the sarking.  
What it doesn’t do, and this is probably what you’re alluding to, is it doesn’t provide a means to get the water out in front of the WB’s in the way that the metal flashing method supposedly does. But I reckon that method is flawed because: 
1.     If you sit the metal flashing above your packers (as shown in the pic from Canterbury Windows install method), then the bottom of your window frame is sitting direct on the metal flashing. How is the water/moisture going to escape? It will be absorbed into the window frame. Plus its going to make it hard to adjust your packers once the window is in if you need to.
2.     If you sit it on top of the packers, then you going to need to leave a gap b/w the bottom of your window frame and the WB that the flashing has to come out over. Then you’ve got a draft entry point. Something I’m trying to minimise. Plus this doesn’t work if you want to put some external trim (ie scotia) under the external window sill anyway.    

> Also, I assume re your point 9 that you will install this under the first weatherboard above the top arc. Easier to install this before you add that board.

  Yep, that's the plan for sure.  
To me, the simplest method is the following:
1.       Sarking trimmed to cover ½ the depth of the exposed timber in the window opening
2.       Butyl tape around all the window opening perimeter (covers both the timber and sarking) and also folded over to the vertical plane (no exposed timber plus the sarking is bonded to the timber).
3.       Window installed
4.       Water proof sealant applied around ALL of window opening 
That window opening is now completely water proof (still use the metal flashing over the top external arc though). Why is this method not used?

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## r3nov8or

> ...What it doesn’t do, and this is probably what you’re alluding to, is it doesn’t provide a means to get the water out in front of the WB’s in the way that the metal flashing method supposedly does. But I reckon that method is flawed because:...

   In a nut shell the flashing is to protect the interior of the home from water (e.g. to help prevent mould), not the window frame itself. Rightly or wrongly...

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## ChocDog

> In a nut shell the flashing is to protect the interior of the home from water

  I definitely get where you're coming from, just dont think the recommended approaches I've seen get the job done as well as it could.

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## r3nov8or

Yep, fair enough. The conventional method is certainly far from perfect. I would imagine that people such as sundancewfs who are very conscious of insulation etc may have a technique you are after. Indeed he may explain what he did somewhere in this excellent thread - http://www.renovateforum.com/f176/ic...project-76617/

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## melton2

have a read of scyon stria installation  http://www.jameshardie.com.au/upload...Feb%202013.pdf
pg 5... 
i used a custom bent flashing for the top of my windows. aesthetically not as nice as it is noticeable to me, but my wife doesnt seem to think it looks out of place.
at least i know no matter how much water hits that area, no water is penetrating the flashing and sarking, even if the sealant gives way in a few years....

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## CraigandKate

> To me, the simplest method is the following:
> 1.       Sarking trimmed to cover ½ the depth of the exposed timber in the window opening
> 2.       Butyl tape around all the window opening perimeter (covers both the timber and sarking) and also folded over to the vertical plane (no exposed timber plus the sarking is bonded to the timber).
> 3.       Window installed
> 4.       Water proof sealant applied around ALL of window opening 
> That window opening is now completely water proof (still use the metal flashing over the top external arc though). Why is this method not used?

  100% with you on this mate, all the published methods I have looked up do not seem very efficient, either for aesthetics, stopping drafts or waterproofing.  
The above method is essentially what i did for my weatherboard shed, didn't even bother with the metal flashing on top of the window. 
1. Sarking wraped into the window opening
2. Window installed
3. Treated pine frame around the aluminium window on the outside (40x40 IIRC)
4. Installed the weatherboards right up to the treated pine frame.
5. Sealed right around the window then around the weatherboards/treated pine frame. (Also sealed between shed frame and window) 
Will most likely do it a bit better for the house, use a metal flashing on the top for instance, but not entirely certain it is required. In this case it is South facing and protected by the eave so I am not worried at all. 
I have it on the house currently but hate the weatherboards running up to the window then the architrave attached to the outside, just creates little spider triangles down each side.

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## ChocDog

> Yep, fair enough. The conventional method is certainly far from perfect. I would imagine that people such as sundancewfs who are very conscious of insulation etc may have a technique you are after. Indeed he may explain what he did somewhere in this excellent thread - http://www.renovateforum.com/f176/ic...project-76617/

  Man, just got sucked into a 4 hour internet vortex reading the thread. That thread is awesome! Most impressed with what sundancewfs did.  More importantly, his shed is even more awesome. Nice gear in there for sure. I remember seeing a little bit of the thread previously but never read it in its entirety. What happened to him, it looks like he hasnt been around for a long time. 
Now, I'd better get back to my day job and recover some of the last 4 hours so it looks like I've actually achieved something...!

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## ChocDog

Thanks for the info melton and Craig. Craig, your shed looks good! Eventually plan to remove the gal sheds here and replace with a proper workshop with WB cladding to match the house. 
Got the windows in over the weekend and very happy with their quality (a couple of pics over in my go to whoa thread). I'm pretty certain to water will be getting in through the window opening...

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