Flashing Problem

Not the raincoat type, the waterproofing type! The attached pictures best explains the problem.

There will be a colourbond roof over the steel purlins. How can I flash between the roof and the weatherboards given that the roof is on a 30 metre curve and the arc created spans three weatherboards?

My idea was to use a piece of standard L shaped flashing and cut the vertical section to allow bending along the curve.Once this was fixed in position I was then going to use a flat stepped piece, the steps tucking up under the weatherboards, with a curved bottom edge to match the roof profile, the idea being that this would cover the "V" cuts made in the "L" shaped flashing. Hope that makes sense:no:

Do you reckon this would do the job or any other suggestions would be most welcome. Thanks.

Terry

The bases of the V-notches will still be vulnerable to leaks. Better to use shorter L-shaped segments, beginning at the bottom of the roof, with successive pieces lapped over their predecessors. The single flat piece (called "counter-flashing") could be difficult to manipulate. That portion could also be done in segments, also beginning at the bottom, and also lapped with their predecessors.

Joe

You would have been much better off flashing that before the weatherboards went on. However, I reckon you could get a sheetmetal worker to make you up a series of flashings to follow the curve and slip up under the weatherboard.

If I was doing it, I would work out where the laps will be (from the height of the flashing and where it intersects the weatherboard above) and then make up several sections, each from two pieces, with the vertical bit scribed to the correct radius and then joined to the horizontal, which would be rolled slightly, with a pittsburgh fold (used in air conditioning ducting to make those radiused bends you see in the rectangular ducts). It will still need to be sealed but I think that would look neater.

Would standard L shape flashing and a few tubes of silicon work OK ?

30 meter curve? I didn't see anything that looked to be 30 meters?

Any way, is the space under the roof going to be enclosed or just a veranda?
If its a veranda you can ( depending on what you use the space for) not flash it as you won't trap any moisture in a cavity. The water will however run down the wall and you'll need to deal with it at ground level, and put a flashing over the doorway

If you want to flash it I would suggest lead sheet , simply because it is maleable and can be dressed on to the curve. Start with the lowest weatherboard tuck it underneath the board and over the roof sheet. Lap this about 3-400 mm under the next length, progressively on each board.
Once you have all the lead sheet in place dress it all down with a rubber mallet.

I have heard some people refer to malleable aluminium sheet/ flashing, I dont know where to get any but this would obviously work the same and not have the health implications of lead sheet.

Bricks,
I think he means the curve is on a 30m radius, at least that's how I read it. :roll:

Terry,
I reckon the neatest way to do it would be to have a section of curved "L" flashing rolled up for you, possibly in two or more sections. I'd then:
Cut the cladding on a curve flush with the roofing sheets.
Remove enough boards above this to fit the flashing.
Cut cladding so it sits about 50mm up from roof and refit. (you may need to fit trimmer nogs to support the flashing and cladding.

Like Silent C said, much better done before the cladding goes on. If it was my place that's how I'd do it, any other way would just annoy the cr*p out of me every time I looked at it.

Mick

BTW

I hope you have been careful handling and disposing of the asbestos cement tiles that were the original calling (as shown in the pics).

Stable and safe enough so long as they are not emitting dust (and they might well be breaking down after so many years) and you need to use masks and disposable overalls etc when breaking or moving them around.

All states have strict rules about handling & disposal of asbestos sheeting (and tiles).

But you no doubt are aware of all that . . .

Correct Mick, I meant a 30 metre radius. A couple of other relevant things; the weatherboards are Weathertex Primelok boards. If your not familiar with them, they have a plastic spline running the length of the board that rests on the board below and the overlap covers the fixing of that board so that you have concealed nailing. All very nice but it makes removal of boards a real problem so I am not too keen on a solution that would require that. The plastic spline also means that the flashing can only tuck up under the board for a distance of 25mm, the overlap distance The other thing is that it is the roof over the front door so it will only be the visitors who get wet if the flashing isn't 100% weatherproof, no threat to the integrity of the structure.

Think I'll take your advice Silent and have a word to a sheetmetal worker. Keeep you posted and thanks all for the suggestions.

I'd start from the bottom with say three steps, just a standard straight "L" shape cut to the angle on the job. Similar to the way we flash to a masonry wall. Lap them well in the length. If you can tuck under 25mm in the height that's enough.

Don't use lead anywhere near Colorbond, unless you paint it well, incompatible materials and all that.

Good photos Terry, attached is one of mine that is less than perfect, but you should get what I mean. The roof shown also has a curve.

Check out my page on metal roofing if you feel like it.

http://www.builderbill-diy-help.com/roof-sheeting.html

Regards
Bill

There's some useful info on flashing roofs to walls here
http://www.pic.vic.gov.au/www/html/1...ons-sheets.asp

How did you get on metung ?

Sorry for the late reply Peter, but I have been "on site" for a while and don't have internet access. I haven't done the job yet because I want to get the blockwork rendered first and the weather has been pretty bad.
I think what I intend doing is using "L" shape flashing with the reverse of the roof curve cut in the the top of the vertical leg. If I then make a series of vertical cuts in this leg, then, according to my theory, the top of the vertical leg should become horizontal and tuck up under the weatherboard when I bend the flashing over the roof. If I make enough cuts then the "V" formed in the vertical leg by the cut should be fairly narrow and I'll fill this up with silicone. I then intend cover the vertical leg with a piece of flat flashing with the bottom face also cut to the profile of the roof. I'll then silicon along this face as well.
Its a shame that it hasn't already been done because it certainly would have been thoroughly tested over the last couple of weeks.
I'll update the thread when I get it done.