How to replace rotting treated Pine on roof?

[vincentb]

I have added some h3 treated pine from Design pine: https://www.bunnings.com.au/30-x-30mm-5-4m-moulding-h3-treated-pine-fj-primed-scotia-losp_p0052884.

These were added on top of a perspex-pitched roof. I also added a few layers of outdoor paint on both sides of these pine studs.

The paint is still solid but inside, the timber has rotten. It looks like rotten by moisture. 

I want to replace these. What are my best options that would last?

Better paint? other product?

Thanks!

[Jewelleryrescue]

Hi @vincentb 

The function of your wood I see is to deflect rain water away from the building if I am correct.  Now  people  can see even treated pine isnt indestructable and it isnt even touching earth/dirt.  Not blaming you  here @vincentb some times treated  wood fails and still gets wood rot.

For this function I would use aluminium flashing in you case 150mm wide should do .

Aluminimum flashing is a thin 0.5mm stripe (you can cut with sissors)  Once timber  board removed You gently lift the plastic roofing 0.5mm and slide the  flashing in under it approx 50mm all the way along. allowing 100mm to angle out deflecting the water as the timber did. some one holding the flashing up and straight while you go along feeding it under the roof will help here.

You  can  Use clear storm silcon to ensure water tightness between the roofing sheets and flashing as well as as to hold it in place.

A few screws  will also hold it in place or tighten the roofing sheets down to act as a clamp.

Try and make sure flashing  under the roof panels is angled up  at same roof angle along the roof edge or  water could siphon backwards under the roof edge. Sealing will prevent this.

All that  remains is to paint the flashing brown to match the room.

[redracer01]

Hi @vincentb 

Have you thought about using an Aluminium angle in combination with Sellleys Storm? It's not exactly pretty but it will last for a very long time. It's also available as a flat bar if that is what you are after. I'm curious how the moulding fits into your roofing structure. Is there any chance you can post a photo of the assembly with and without the moulding?

Aside from that the only other material I can suggest is Sunlite 8 1.2 x 0.61m Clear Twinwall Polycarbonate Sheet. You'll need to cut these into strips so that they fit your installation needs. They come in longer lengths and can be attached with silicone.

If you need further assistance, please let us know.

Happy Holidays!

Red

[vincentb]

Hi all! 

Thanks for all the great advices!

Iam still not understand why h3 pine has rotten so fast but I need to accept this and move on to the next material: I think I should go to aluminium (an upsidedown V shape) would work well. I am just confused if the sun will heat too much the aluminium (dark painted) and accelerate the deterioration of the silicone.

I am going to have to research the right silicone sealant: needs to resist hi-temp, be flexible, water-resistant and bond to polycarbonate. As I will need quite a lot. is the cheap parafix roof silicone a lot worse than the more expensive brands? 

Happy festivities everyone!

[MitchellMc]

Welcome to the Bunnings Workshop community @vincentb.

I do apologise for the issue you've experienced with this timber. It's odd, as the timber you've linked to is perfectly fine for exterior use and shouldn't rot for a considerable amount of time, such as a decade or more. How long has it been up for? The only reason I can really think of that could cause an accelerated decay would be if water was able to penetrate the timber and then get enclosed in the paint, keeping the timber constantly wet. Is there a chance water could have seeped inside the painted coating? Did you puncher the coating at all with screws, not paint one side etc.?

The Parfix 300g Clear Roof Gutter Silicone is a great silicone suitable for our harsh environment. It's designed to withstand the heat associated with metal roofing and guttering. If you're sticking to a budget, I don't think you'll have any issues with this silicone.

Please let me know if you have further questions.

Mitchell

[Dave-1]

Afternoon @vincentb 

Love that roof! Seriously it looks stylish. What a nice addition to your yard!

Tho when I looked closely at the picture I have an idea on why its rotted.
I followed the link you posted but thats for an underside style use? 

From what I see you have the beams that are vertical (painted black) then either side you have attached something to them to allow the perspex to be mounted on top? If this was the case, how did you seal the perspex and timber? or did you use the molding that you posted the link to? If the seal wasn't the best then the configuration would have allowed water to potentially seep in and pool, that would account to why its rotted?

Any chance of some photos of closer up from above and below?

Dave

[vincentb]

Hi Dave, Thanks for the love of this roof! this was done just after buying the house: made on a non-existent budget! I am so happy with the design and the function. All materials are still going strong after a few years (the pivot door, louvres windows are all handmade with h3 roof rafters)

I think you must be right! water might have found a way under the cavity, got blocked and slowly rotten the h3 pine! 

[Dave-1]

Afternoon @vincentb 

Id definently be trying to figure out how to replace those rafters, the rotted ones with a similar product that is more weatherproof or a product that will seal those panels I really like that style of roof

Dave