How to replace box gutter that is corroded and leaking?

Question

Hello

My existing box gutter in between house and rear patio always gets full of leaves and is now corroded and leaking into the patio below. I'd really prefer to just get rid of this if this is viable, and install a new single piece roof sheet - Trimdek? I've been warned that doing this will add further rainwater to the house gutters. I currently have 4 gutters, all with rain heads (leaf eaters). I'm assuming a new gutter will run all along its edge. The existing back gutter is fairly new. Could this be fitted to the new sheet?

This is my existing set up.

First photo is the box gutter (leaf litter has since been removed). Second photo shows there are 2 separate roof sheets (box gutter is hidden). 3rd photo is overhead showing the patio with the blue stripe. So 2 existing sheets would be removed and just 1 roof sheet is put in placed under the top gable - is that right? And the new gutter would go all around this perimeter?

I'd really appreciate a photo & maybe description of what this would look like. And also, are there any risks with the new roof - greater risk of wind uplift instability? I'd like to know what I should be asking for exactly - including a rough idea of cost - specifications of screws & anything else I need to ask for. Thank you and really appreciate your help.

Nailbag · Answer

Hi @LorenClayton

These are really questions that in my opinion can only be answered by roofing plumbers who have been on site. My main concern in the first photo is the very narrow opening  between the two roof lines and what sized guttering is in place taking all that water? I would be very surprised if you're not getting internal water ingress during heavy rain events when the gutting is full of debris. It only takes one stick to start a blockage at a down-pipe entry point to flood the gutters.

As @JacobZ mentioned, you can't just increase the guttering size without effecting other sections it's contained within, structural or not. I've just had major roof and guttering rework completed. Two valley sections had a single gutter taking all the water. So both roofs were raised so that they had their own guttering, which then drain into a new common single one. This 2-story guttering system slows the water runoff to prevent overflow and makes for easier cleaning. Of course all this work was designed and implemented by dedicated roof and gutter plumbers.

Nailbag

Dave-1 · Answer

Good Afternoon @LorenClayton

If you are wondering if its possible to install something that slips under the roof part and then over the patio part id be cautious of doing that. Mainly because it ties your house and patio together which may not be allowed. :/

I like the idea of replacing the existing box gutter and keeping the seperation between the two structures. As you are effectivly doubling the runoff to the patio roof/gutters. I keep ending up heading towards a person with professional knowledge with what is allowed and capacity knowledge as to what the roof can take. You could do what my first part describes, I am unsure if its wise :/

Dave

JacobZ · Answer

Hi @LorenClayton,

I'm not sure I follow. Are you asking if you could essentially have the box gutter removed and have the roof sheets run down from the gable, over the patio in one continuous run?

If that is what you are asking, then I don't think this is possible because you are working with two different roof pitches and as far as I am aware, you can't run a single roof sheet with a bend in the middle and at different angles. There would also be structural implications for this as you would be tying your patio to your existing roof in a way that wasn't originally intended or engineered for.

There may be a way to bridge this gap using custom flashings, but I can't say I am certain if this is possible or not.

Realistically, this would be a question best asked of a roofing plumber. They should be able to advise what is and isn't possible in this situation.

Allow me to tag @Nailbag, @Dave-1 and @Noyade for their thoughts.

Jacob