Home Renovation & Building Forum
https://forum.homeone.com.au/

How to fix overflowing gutter with new Pergola
https://forum.homeone.com.au/viewtopic.php?f=17&t=63191
Page 1 of 1

Author:  Nick82 [ Feb 26, 2013 9:56 am ]
Post subject:  How to fix overflowing gutter with new Pergola

I have recently completed installing a new Pergola over my existing Deck at the rear of my house.

I have a problem where the roof of the pergola meets the house. The height of the Pergola roof is higher than the existing guttering. I did not want water coming through onto the deck in heavy rain so I installed some flashing which seals between the gutter and the laserlite roof. The problem now is in heavy rain when the gutters overflow the water now floods back into the eave of the house. I wanted to get some ideas on what is the best way to fix this. I could either remove the flashing and allow water to overflow onto the deck in heavy rain but that removes the point of building the Pergola. has anyone had this problem before and have a nice solution?

here is a picture I drew up so better explain my problem. You can see the red line which is the flashing I installed.


Author:  SaveH2O [ Feb 26, 2013 11:37 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

What you have done is create a very high High Fronted Gutter.

If the gutter was installed to compliance, then it would have complied with AS/NZS3500.3 2003 Section 3.5.1 that states: Eaves gutter systems, including downpipes, shall be designed and installed in accordance with Clause 3.2 so that water will not flow back into the building.

As I cannot see the gutter, I don't know what the continuous overflow provision would have been but if it was flashing at the back of the gutter, then the flashing you have installed would no doubt over top that flashing.

Regardless of the previous continuous overflow provision, it would have overflowed to atmosphere but you have now prevented that happening.

The diagram indicates that the back of the gutter is fitted level with the top of the fascia. This is not compliant if the diagram is correct.

The diagram also indicates that the back and front of the gutter are the same level. I have doubts that this would be the case.

The diagram also indicates that the pergola roof is sloping away from the gutter!

If the pergola roof drains to the gutter and the gutter cannot cope, then the total roof area now drained to the gutter is not compliant.

I could possibly suggest a very easy and inexpensive fix but I would be breaking forum rules to do so as it involves one of my products. Regardless of that, I would still need to see proper photos before commenting further.

Author:  Nick82 [ Feb 26, 2013 12:19 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Thanks for your feedback, I will get a photo and post it up as soon as I can.

To answer some of your queries, yes the back of the gutter sits level with the top of the fascia, but I believe the front of the gutter is lower to allow overflow. Sorry my drawing is not 100% accurate.

I had some other ideas to solve the problem:

1: install more flashing on the rear of the gutter up and around the first roof tile.
2: put some more roof sheeting tucked under the second tile and fixed to the laserlie on the pergola roof, effectively covering over the gutter so the water flows straight onto the pergola.

I am new here so if posting details of a product of yours is against the rules then that's a shame as I would be interested to know.

Cheers
Nick

Author:  bashworth [ Feb 26, 2013 12:41 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Install at least one more downpipe might be a help.

Author:  SaveH2O [ Feb 26, 2013 3:34 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Nick82 Nick82
yes the back of the gutter sits level with the top of the fascia, but I believe the front of the gutter is lower to allow overflow.

I am new here so if posting details of a product of yours is against the rules then that's a shame as I would be interested to know.


Hi Nick,

I am assuming at this stage that you have decking or paving under the pergola that would make fitting a downpipe difficult. If you can post some photos, it would be good as I would also like to see the decking if applicable plus the location of any downpipes.

The gutter should not have been fitted level with the top of the fascia as the regulations prevent this. There is an applicable calculation, referred to as fh from memory, that covers this. The calculation is too difficult for most people to work out and most plumbers just use a measure of 20mm at the back of the gutter's highest point to the top of the fascia. I am sure that this would also cover low fronted gutters as there is the gutter slope to consider...I might check later to make sure but it doesn't really matter here.

A low fronted gutter does not require addditional continuous overflow provisions such as flashing as I mentioned as it's very design prevents over topping back to the eave or wall cavity.

Forums frown on direct links to proprietary products as it would generally be considered spam. This particular forum is very good however but I think that I would need a sponsor/advertising link and I haven't acted on seeking information in this regard. I have been thinking about it.

The solutions you are possibly looking at doing are messy. You need to remove the water. I will wait on the photos before deciding the next step. Where abouts are you?

Author:  Nick82 [ Feb 26, 2013 7:24 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

SaveH20, thank you so much for your assistance so far. Here are some photos I just took to better explain my situation. I pulled back a tile and found that the existing gutter sits about the same height front to back and sits flush with the top of the fascia as mentioned earlier. The house was built around '88 and I believe it to be the original guttering. I have one down pipe at the end as pictured and another at the other end of the house. Adding another in the middle I gues could be possible but would not be very pretty. I am located in Canberra.

   ⋅  Add a comment  ⋅  Pin to Ideaboard  ⋅  





Author:  SaveH2O [ Feb 27, 2013 1:13 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Hi Nick,

Thanks for the photos. A little different to how I imagined it but overall pretty close.

Downpipes fitted at the end of walls are very common unfortunately.

I am guessing that the halfway point along the wall is slightly to the right of the open door. This is where the gutter's high point should be. The high point determines the gutter's slope and the roof area harvested but looking at the first photo taken from the other end, I notice that the back of the gutter is still at the top of the fascia. This indicates that the gutter has no slope. This observation is reinforced by the dirt pattern in the gutter.

The pergola roof is also a fair size. There is really only one solution and that is another downpipe as suggested by bashworth. I thought about a couple of things but the problem comes back to the concentrated flow off two rooves during heavy rain discharging to a gutter with minimal slope and the distance between the downpipes. If you call a plumber, he will probably say that you need a bigger downpipe but I am absolutely sure that this would not solve the problem although it would help to a degree.

The downpipe would be best plumbed so it came down the RHS of the small brick wall between the sliding door and the windows on the right...if that makes any sense. It would look ugly and you might also have an issue with the deck in regards to plumbing the new downpipe to the storm water.

However, what I propose that you do is to have a look at something that I will PM you a link to and if you want to try it, I will send you one N/C. Instead of having a downpipe, you will have a 20mm pvc pressure pipe that you can paint and it will be barely noticed as it will go horizontally under the eave to the wall and then vertically down the wall. From there, it would either go under the deck to the downpipe (if possible) or along the floor/wall intersect to the downpipe.

You will need to spend about $20 on some 20mm pressure pipe and fittings and you only need to drill one small hole in the gutter. It will provide a more than adequate flow rate as the device increases the pipe's flow rate by 1,000% or more.

The first thing to do though is to run a hand broom along the gutter to better the roughness coefficient to improve the flow.

Author:  Nick82 [ Feb 27, 2013 7:25 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Awesome, I will look at that today. A few points from what you have said, yes the gutter appears to have no slope towards the downpipe, which is evident as after rain water does pool in the middle of the gutter. Also the pergola roof slopes away from the gutter, not towards it, so any rain onto the pergola flow off the edge, not into the gutter. I am thinking that an extra downpipe fitted between the door and window might work. It would be a bit hard to fit as it involves cutting the deck to get it through but under the deck it could angle across and connect to the existing downpipe at the end.

Author:  building-expert [ Feb 27, 2013 8:00 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

I think bashworth solution is practical as well, or a bigger downpipe 100x75 instead of 100x50, although if you need to get rid of a lot of water in a hurry you should consider a rainhead. As for lack of slope in a gutter(I can already see some rust), I would just paint inside with bitumen emulsion based paint (available at Bunnings) which will increase longevity before full corrosion.

Author:  SaveH2O [ Feb 27, 2013 10:00 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Nick82 Nick82
yes the gutter appears to have no slope towards the downpipe, which is evident as after rain water does pool in the middle of the gutter.

I noticed that a couple of mm was showing at the top of the gutter near the middle.

Nick82 Nick82
Also the pergola roof slopes away from the gutter, not towards it, so any rain onto the pergola flow off the edge, not into the gutter.

Ok, that clears up a few things that were nagging me. I was looking at the flashing attached to the pergola roof and scratching my head plus I couldn't see how the diagram could have been mistakenly drawn with the roof sloping the wrong way. This does however lead me to now think that the gutter has been overflowing ever since the house was built and not just since the pergola was added!

Nick82 Nick82
I am thinking that an extra downpipe fitted between the door and window might work. It would be a bit hard to fit as it involves cutting the deck to get it through but under the deck it could angle across and connect to the existing downpipe at the end.

You need additional drainage, there is no way out of it. If you have the room under the deck to divert a new downpipe to the other downpipe, then the downpipe would need to be a 90mm round PVC and the 100mm x 50mm downpipe at the end would also need to be changed to a 90mm round PVC so that the two pipes can couple.

How far is it from the end of the pergola (near the door) to both downpipes? The fact that the pergola doesn't drain to the gutter changes the best positioning of a new downpipe quite a bit.

How much and whereabouts does the gutter overflow? I was assuming that you had the pergola roof also going into the gutter but given that this isn't the case, changing one of the downpipes to a 90mm round might be enough although in situations like this where the downpipes are fitted at the end of the walls, the gutters nearly always overflow halfway between the downpipes. How far apart are the two downpipes?

Author:  B STAR [ Feb 27, 2013 10:41 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Is it possible that the rain is being pushed through the sheets and under the flushing??
Nick where do you have issues with water coming through? Is it in the middle or the whole way. Sorry if you have already answered this.

Author:  Nick82 [ Feb 27, 2013 10:48 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

I would need to measure the house but to give you an idea in that photo the mid point of the house would be around just to the left of the door as you look at the photo, so the downpipe pictured covers the whole area of the pergola, and the other downpipe covers an equivalent area of roof not shown in the photo. So in a nutshell the Pergola covers roughly 40% of the length of the house.

I like the idea of the product you showed me, this could hopefully be the answer I am looking for. Either that or install a conventional downpipe.

Also I entertained the idea of installing a rainwater tank under the deck some time back when we had strict water restrictions in place, but lost interest when the restrictions were relaxed. I am thinking to do this again now as I can use this downpipe to divert into the tank.

Author:  Nick82 [ Feb 27, 2013 10:50 am ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

B STAR B STAR
Is it possible that the rain is being pushed through the sheets and under the flushing??
Nick where do you have issues with water coming through? Is it in the middle or the whole way. Sorry if you have already answered this.


The water is leaking through between a small gap between the gutter and the fascia ~1mm. SO in heavy rain I get water streaming onto the deck.

I also have noticed some water staining on the eaves which brought me to realise that water was getting into the roof cavity.

Author:  SaveH2O [ Feb 27, 2013 12:14 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Nick82 Nick82
the mid point of the house would be around just to the left of the door as you look at the photo

This means that you could possibly fit something to the left of the pergola. Unfortunately, I cannot see that side but another drain doesn't necessarily have to be close to the middle as there is no high point. Overflows also often appear larger in volume than they actually are as they come over in sheet form.

Nick82 Nick82
I like the idea of the product you showed me, this could hopefully be the answer I am looking for. Either that or install a conventional downpipe.

A plumber would probably charge $400+ to install a new downpipe, change another downpipe to a 90mm round and then connect the two downpipes unless A.C.T. plumbers work at cheap rates. You could fit the other product yourself and it would cost about $20. You can also divert that water to a tank.

Nick82 Nick82
Also I entertained the idea of installing a rainwater tank under the deck some time back when we had strict water restrictions in place, but lost interest when the restrictions were relaxed. I am thinking to do this again now as I can use this downpipe to divert into the tank.

I can't see the available space under the deck but going by the lay of the background fence, there doesn't appear to be a lot of room. Were you considering bladder tanks?

Bladder tanks are expensive and the water quality needs to be good unless there is a quick turnaround of the water stored. If you decide to do anything in this area, ask for advice in Eco Living. There is a lot of information to pass on that would save you heaps. I will PM some basics.

Author:  Nick82 [ Feb 27, 2013 1:58 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

There is approx 1 metre in height under the deck, I investigated slim tanks that would fit at the time.

I am thinking I will take you up on your offer using your product. Do you think that this will be successful and do you think it will work better than a standard downpipe?

The problem with installing the downpipe to the left of the door is that there is a hot water unit between there and the downpipe at that end, and I would prefer to hide some of it under the deck. Also I think that locating it between the door and the window is closest to the problem and therefore will be the most effective.

Author:  SaveH2O [ Feb 27, 2013 2:47 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

It is not a downpipe replacement, it supplements the downpipe during major rain events, only works during heavy rain and drains as fast as 3 garden taps.

No point paying hundreds of dollars when you don't have to.

Just PM a mailing address.

EDIT: The product discussed was the Supa Gutter Pumper. https://gutterpumper.com.au/

Author:  SaveH2O [ Mar 01, 2013 5:09 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Hi Nick,

If there is room to run the 20mm pipe down the wall to the left of the door, then this would be the best place to fit it. The greater roof area drains to this area of gutter and the device will pull water from both sides of the gutter. This will assist both downpipes.

You should also look at running the pipe down the RHS side of that wall section as this should also allow you to drill a small hole (about 28mm diameter) through a decking board for the pipe.

Access and fitting will also be much easier.

Author:  Nick82 [ Mar 01, 2013 9:30 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Thanks for the tips, I plan to install it between the door and the window, as that is the most central location where it can be connected to the downpipe.

Author:  carinya [ May 29, 2018 4:26 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Nick82 Nick82
Thanks for the tips, I plan to install it between the door and the window, as that is the most central location where it can be connected to the downpipe.

Hi Nick,


Just wondering if you have solve the problem? My old house has a similar problem and I am looking for solutions as well.

Regards

Tom

Author:  Nick82 [ Jun 04, 2018 2:37 pm ]
Post subject:  Re: How to fix overflowing gutter with new Pergola

Hi Tom,

Yes I can happily say it has fixed the problem using a gutter pumper. However you need to regularly clean the inlet in the gutter as it clogs up with leaves easily which blocks the flow. If you also use some gutter guard then I would say this would fix it from blocking up.

Page 1 of 1 All times are UTC + 10 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
http://www.phpbb.com/