How to build a gravel path and drainage?

[FernyG]

Hi Bunnings Community,

Long-time reader, first time poster, thanks in advance for any advice and apols … my photos got in first and questions are below 😊 👇

 

 

 

 

 

 

My problem

• Previous owners laid pavers and stormwater drainage pipes too high beside my house, plugged up the weepholes in bricks for years and caused rising damp inside lower level (just fixed professionally and quite spendy).
• Problem exacerbated by use of an ag pipe (also previous owners) for part of the stormwater beside the house instead of a PVC pipe, connected into downpipes.

The area

• We are in Queensland - not in a flood zone or any problems in that regard - but it rains a lot and storms can be big. 
• Some water flow comes down from the back garden (terraced) through this area when it rains but does not pool and has always drained off quickly through the pavers. Backyard drainage is fine.
• The side of the house is 11m long and 1.45m wide so not a lot of area to play with.
• Clay type of dirt, high water table after years of rain.

The project (see drawing)

1. Removal of pavers (partially done) 
2. Dig down to bring ground level lower than bricks (currently at least 15cm above the bricks, we're hiring a kanga)
3. Slope the ground away from the house and create fall down to where pipe will join stormwater (there is a nice existing fall once you get past the side of the house towards the front) 
4. Trench and installation of PVC stormwater pipe at correct level (will get plumber for connections) - will use 20mm drainage gravel all around pipe and wrap in geofab 
5. Create a gravel path with 600mm x 600mm paver steps 
6. Plan is weed mat + pins, roadbase or 20mm gravel (100mm deep), compact, sand (50mm? deep), compact, install pavers, decorative gravel (50mm deep).
7. Lift old pavers out front of the house and reuse side pavers, as well as another gravel path. 

Questions - apologies, there are a few  

Materials - There is a LOT of material there now - at least 150mm above the bricks in places so I believe we need to dig out 300mm then put in the base/sand/gravel for 150mm then we're ideally 150mm below the bricks. And how far we dig the trench for the PVC pipe depends on height of stormwater connection (don't know that yet as pavers are not up). 

As pictured, I think what is there now is sand and roadbase (see pictured). We are going to have to dig out so much to dump in a skip, and planned to buy new stuff, but is there a way to reuse? 

The problem is it'll be all mixed up and the material will have grass/weed seeds all through, weeds have been a real problem and want to resolve that as well. Could we maybe do the first 50mm layer old dirt and compact, then weedmat, then 50mm fresh roadbase or gravel? Gravel appeals more for drainage benefits. Then 50mm sand, then 50mm decorative gravel.  

At least then we'll only have to buy half as much roadbase / gravel. Is there a risk the flow from the garden will wash the gravel away if we get a big storm?

Slope

Slope away from house (side): 50mm for first metre I think, then what? The slope away from the house will be towards the raised beds. We had thought about an ag pipe there as well but want to keep it simple.

I'm not clear how we lay the pavers to be flat down the centre if there's a slope?I know the fall to the stormwater connection is minimum 100mm per metre.

Trench 

How far out from house to trench to install the PVC stormwater pipe but still connect to downpipes. The downpipes are new and the plumber said to angle out from the house as much as possible as the old ones were flush and have rotted wood in our cladding.

The trench may not be that much lower than the rest of the ground level depending on fall requirements. If we wrap geofab and surround in gravel does it need to have something to separate it from the 'rest' of the gravel / roadbase for the path? Otherwise it is just sitting all at the same level. But then if we put in a metal separator or something that might trap the water by the house (again) ... sorry I'm not quite sure how to phrase this question. 

Thank you for reading if  you got this far!!   

[Dave-1]

Good Afternoon @FernyG 

Now thats a decent sized job Nice work and also nice thinking.

When I went through the same type of questions and issues as you have I was happy to have the path below the weep holes on my brickwork. I also used gravel as the underlay of my pavers. I think I have around a 50mm drop from the weepholes to the path at least.

With the weep holes exposed and te gravel I have not had any water enter via the mortar/fine cracks inthe brickwork Its all funneled down the path ad then out to the garden. (Will include my project links in a sec )

Do you have access to under the house to see what the condition is? As a workaround you could use the concrete garden edge lengths back to front like I have in the Side path rebuild to provide a high barrier for your weep holes? That way you allow air in and may not need to remove so much clay?

It is a big job as yours is, You are stepping through it with well thought out ideas  

Stormwater rectification stage 1 

Stormwater rectification stage 2 

Side path rebuild from recyled pavers 

If you look at the side profile of my stormwater pipes and path. 

Down the center is a trench 500m deep ish

Within the trench, 30mm gravel, then 100mm DWP PVC piping, all back filled with 8mm gravel to around 40mm above the pipe.

Then a layer of clay across the trench to bring it level.

The underlay of the pavers is the same 8mm gravel

The Slope I shaved so it was a constanat fall. 

The edge needed a gutter as I have water from my neighbours flood in

The path has stood up for the past two years with no maitenance needed.

Dave

[FernyG]

 

 

Hi @Dave-1 @EricL @Nailbag - wanted to get a view on a pickle we are in. We have dug down very far. There’s a 500mm drop between our house extension and the footings of the brick house. The plumbers are trenching (down the centre with 3 x pits) but it looks like they may not be able to get the fall bc of the level of the pipe to the street. Where they have dug so far is not beneath the house footing level. So I am not sure how we manage that… could we waterproof the bottom brick and go up with gravel to just underneath the weepholes? Noting the inside is waterproofed. It’s really not ideal. 150mm below the weepholes will be under the house footings.. we wanted to do 100mm road base to footing level, then 50mm of decorative gravel so it was 50mm above the first brick (75mm high) and the weepholes are just below 2nd brick up which is the weepholes. BUT - looks like the trench isn’t even that low now 🥹 Stressed! And advice? 

[Dave-1]

Afternoon @FernyG 

The fall to teh street dosnt have to be steep and the plumbers would know for sure what the mininmum should be.

The weep holes I would really try to keep open and even have a drian or a gutter to allow water to flow away quickly and air to circulate freely through the weep holes. I have gravel up to around 40mm under the weephole in one short section (yeah checked it the other day when we were commenting)

So the soil has been put in after the house was built causing you issues now. Does the soil slope downwards or up as it travels down teh side of the house? When I did asked my plumber hios recomendation about redoing the stormwater pipe he said you can always attach it to the side of the building. I dont really like that idea but for your downpipes depending on your slope and how it slopes to the street may need to be above ground. The water on the path if the path drops going away from the street, maybe you could drain that seperatly ?

My trench was generally min 300mm at the very top deep and gradually stretched down to 600mm and at its deepest it was up to my chest height , 1.2m deep.  If your plumbers have suggestions I would be weighing their ideas heavily as they are the ones doing the work.

Dave

[FernyG]

Thanks @Dave-1 - to be honest they only started digging this arvo so they may well intend to go lower. I may be panicking unnecessarily. I’ve let them know the issues about weepholes and the bricks needing to be above ground etc. I think best case scenario will be gravel 50mm beneath the weepholes though. Our waterproofing guy who did the inside thinks that’ll be ok bc the inside is all waterproofed. 
We intend (if possible) to grade the angle away from the house and have 3 x grated drains attached to the pits down the centre to capture the surface water into the pipe. 
The slope to the street from the front of the house is pretty reasonable, alone the house it’s a gentle fall. 

Yes, we think when they built the extension they must have just built up the dirt beside the house to manage the level difference. Which seems insane but it was 1984. Then the previous owners built up even more with roadbase / pavers etc. Nightmare. 

Thank you for your advice, I read through your project after your last comment - great job! 

[Nailbag]

Hi @FernyG 

I wonder if there is an option to install an automatic submersible pump system to push the water against the fall to the mains stormwater. Had a a neighbour once who had one connected to a toilet in an add-on ensuite that pumped the flush automatically up the side of the house, across the roof and down then along to the sewage line. We always joked as to what might happen if the roof line broke!

Nailbag

[FernyG]

Thanks @Nailbag - that’s an interesting thought. We did have a quote from a company which suggested a French drain - before we realised the actual stormwater was busted - to manage the damp. They suggested a pump to save having to go under the garden bed would be more economical. Quote was $14.5k 😱 for 13m of drain. Suffice to say we have a different plumber. They also did a wildly expensive gutter quote too. 

That aside, the pump is a reasonable concept if the fall can’t be achieved. Anyway, fingers crossed tomorrow it’ll all get sorted! 🤞

[Nailbag]

Hi @FernyG that quote is unfathomable.

I used to live on the side of a mountain and though a different scenario, I had severe water run off under the house. A few ag pipes and a $99 Ozito submersible pump later it was resolved.

Nailbag

[EricL]

Hello @FernyG 

I was thinking along the same lines as @Nailbag. I propose looking at the Everhard 325mm Series 300 Shallow Stormwater Pit and the Ozito 350W Dirty Water Submersible Water Pump as possible candidates for the drain system.

Eric

[FernyG]

Thanks @EricL & @Nailbag - events I overtook us. Turns out the pipe the plumbers were to connect into has actually been cut off by the council when they put in a new street drain. It was old and clay, so they may have thought it was unused. They cut it very neatly and put the concrete block rectangular street drain in front of it.. but no hole for my water. Cue plumbers with excavators digging up my garden, going under the street pavement to put through a new pipe. But the pipe still couldn’t be deeper than the footings of the house so my options are: waterproof the wall and put soil back against (waterproofing guy says that’s fine, builder friend says crazy to cover weepholes). Or build a retaining wall with three sides, have the dirt in front of it levelled, but behind it is gravel slightly lower than weepholes. Grade the dirt away and drain down the middle is meant to take care of the water. But then I’ll have two raised beds with no ag pipe and I am uncertain the water will run off. But the weepholes will not be covered. Any thoughts on these ideas? 

[Nailbag]

Hi @FernyG 

I like the idea of waterproofing and back filling the wall, but I also agree with your builder mate to definitely not cover the weep holes. 

So, I would ask him if he thinks if  installing some form of ventilation box in front of each weep hole?

I was thinking a PVC  down-pipe with the back cut out at the vent and sticking up above ground height say 100mm with some form of raised angled cover to prevent rainwater entering but still allow air flow. 

Nailbag.