How to fill gaps between box gutter and adjacent roof?

We have had issues with the backup of water due to the downpipe from our box gutter getting clogged and also with the box gutter not emptying properly into the header box for the downpipe , even if the downpipe isn't blocked. For either or both of these reasons, the water can sometimes start ponding in the box gutter itself during heavy rain. The gap between the box gutter, the wall and the colourbond roof was never filled by the builder, so if the water builds up in the box gutter and reaches the level of the gap, the water leaks into the wall (and from there into the interior of the house e.g. around the window frames on either side of the downpipe).

We have cut a hole in the base of the downpipe to prevent the water from backing up but there is still a potential problem with flooding due to the box gutter not draining easily into the header box for the downpipe. As you can imagine, access under the toe of the colourbond roofing sheet from the inside the box gutter is difficult (see photo, just to the right of the boot that you can see), so normal silicone caulking using a caulking gun would be difficult or impossible. I am thinking the easiest solution is to spray expanding foam into the junction between the colourbond roof and the top of the wall / interior side of the box gutter, using an applicator nozzle. Even if the foam is supposed to be waterproof, I'd probably then spray the foam with Selleys Roof and Gutter Spray Seal or similar. However, I can't find an expanding foam that specifically says it's waterproof (maybe they all are so they don't bother saying?), and the Selleys spray says it may be incompatible with some plastics eg. polystyrene, so I'm worried it will damage the expanding foam rather than seal it

It'll be a bit of a bodge job but short of some major dismantling of the roof and / or gutter, it seems the most practical solution (and no-one will see it so the workmanship doesn't matter). Any recommendations on:

Is this the best solution? If not, what would you recommend?

What is the best (ideally waterproof) expanding foam to use?

If a sealing spray should be applied afterwards, which one is best to use and won't damage the expanding foam?

Many thanks in advance 🙂

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Comments

JacobZ

Hi @Caversham04,

Welcome to the Bunnings Workshop community and thank you for your question.

I'll start by saying, please be extremely careful. I'm sure you are aware of the risks of working at a height like this, but seeing someone on an exposed edge with no edge protection is very concerning. For this reason alone, I would say this is probably a job left to the professionals, but I will try to help assess the situation regardless.

I'm struggling to understand where exactly the issue is, so I'll ask a few questions to hopefully clarify.

Is the area where you are thinking of spraying expanding foam inside the wall on either side of the gutter?

Is the issue that the water is backing up in the header box, then when it backs up above the level here -

- it is backflowing into the box gutter that runs through the wall, where it spills down into the wall?

If that is the case, I would think the best way to address the problem is to prevent the header box from backing up to the point of overflowing.

There are expanding foams that say they are waterproof, such as this Parfix Expanding Foam Filler; however, I am sceptical that they would be able to create a watertight seal in an area that you can't really see.

It could be worth a try, but it is a bit of a band-aid fix for an issue that seems to be due to a failing header box.

Personally, I would be getting a roofing plumber to assess the viability of the header box and whether it is a suitable size for the task. I would also be looking to cover the header box with some gutter mesh to prevent it from clogging up with leaves and debris.

Allow me to tag our experienced members @Dave-1 and @Nailbag for their thoughts.

Let me know what you think.

Jacob

Dave-1

Good Morning @Caversham04

Looking at your pictures and going over your description I am thinking of actually removing the box and the open gutter through the wall and replacing it with a PVC pipe and connecting it to the gutter directly. Not sure on the ruling so that might be worth looking into.

As to the box filling with leaves, maybe some mesh on the roof sid eof the wall to stop debris from entering the gutter there before it gets to the box.

You say you have cut a hole in the base of the downpipe, to preven water from backing up. Have you had the stormwater pipes looke dat to make sure they are free. When I had my gutters replaced, I then had water coming out of the base of my downpipes, yeah the issues kept on going down the path 🙂 If you water has backed up from the stormwater pipes, then the downpipe fills, then the gutter box... It may be why you have ended up with the leak you have.

Id check the free flow of stormware via a plumber and a camera (hose down the pipe dosnt fake a storm 😕 )

Mesh to stop leaf matter in the first place, regular maintence of the mesh to make sure nothing builds up.

Maybe even change the box so the base of the box slopes towards the downpipe point so water cant sit there.

Dave

Caversham04

https://www.workshop.bunnings.com.au/discussion/comment/54618#Comment_54618

Hi Jacob

Thank you for the reply. Before I give some more details, you'll be pleased to know that the photo was taken by a professional handyman who was using a safety harness!

You're correct that the header box doesn't seem to be draining very well, but there is also a problem with the box gutter not draining very well into the header box, even if the header box itself is not full of water.

Hopefully the photo below gives a better idea of where the gap is that needs sealing. Dave-1 has separately suggested getting the header box and downpipe sorted out professionally, which is a valid comment. I'd probably still like to seal the gap too, so I've covered both issues that are feeding into the overall problem!

Gutter image.jpg

Caversham04

https://www.workshop.bunnings.com.au/discussion/comment/54627#Comment_54627

Hi Dave-1

Thank you for the suggestions. I've given some more details of the issue in my reply to Jacob. I'll probably look at filling the gap still (this can be done quickly) and also sorting out the poor drainage from the box gutter via the header box into the downpipe (getting someone in to do this may take a few weeks). The downpipe used to feed into the water storage tank but is now freeflowing (sometimes) to ground on the path beside the house.

Cheers

Caversham04

Nailbag

Hi @Caversham04

when it comes to any internal water ingress issues, especially from a 2nd story roof, then "bodge jobs' in my opinion are definitely not the way to go. The potential to slow or simply redirect the water internally without any obvious immediate issues is highly likely to raise its ugly head downtick at major expense and heartache. When you apply foam into an internal space you can't see the final result from is to hit and miss. Plus expanding foam is not a waterproofing solution.

I'm inline with @JacobZ recommendation to get a plumber who specialises in roofing to fix the issue or I would probably start with a leak detection service. This is the type of issue they can find the source/s of using infrared scanning cameras. Their report will then enable you to either fix the issue yourself or get a plumber in.

Nailbag

EricL

https://www.workshop.bunnings.com.au/discussion/comment/89590#Comment_89590

Hello @Caversham04

I can only suggest installing a Rain Harvesting 90mm Leaf Eater Original Rain Head on the header box drain pipe and Jack 1m StayMesh Plastic Ultra Gutter Guard Strip - 5 Pack in leaf prone areas. By pre-empting the leaves and debris, it should provide you with better flow in your box drain pipe. In regards to sealing the box gutter gap, I'm currently unaware of an expanding foam that's 100percent waterproof when applied.

As an alternative solution, I suggest speaking to your plumber and asking if it is possible to install an emergency flooding drain in your box gutter. It will only be in use when the water reaches a certain height in your gutter. But the majority of the time rainwater will only pass through the regular drains.

If you need further assistance, please let us know.

Eric

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