As in west suburbs of Melbourne? Deeper than you care to know lol
HaHa
Browse Forums Building Standards; Getting It Right! Re: Wall cracks, building footpath as per CSIRO BTF18 41Jan 07, 2023 6:17 pm Noname groundzero Do you know how deep the clays on the west side? As in west suburbs of Melbourne? Deeper than you care to know lol HaHa Re: Wall cracks, building footpath as per CSIRO BTF18 42Jan 07, 2023 6:18 pm groundzero Noname groundzero Do you know how deep the clays on the west side? As in west suburbs of Melbourne? Deeper than you care to know lol HaHa Core samples from geo tech reports 2-2.5m down had clay of some description on all blocks I've built on. Dark matter scientist, can breathe underwater, mind reader and can freeze matter just by willing it. Trust me, its in my sig. Re: Wall cracks, building footpath as per CSIRO BTF18 44Jan 07, 2023 6:55 pm Lisa06 groundzero Do you know how deep the clays on the west side? Geotech report states approx 500mm fill and 500-1800mm clay Should be class "P". If you want to put in a cut off drain/agi drain then it should go down to 500-600mm deep into the natural clay if there is moisture seeping through the sub surface soil. Do you think the moisture is coming from the surface only or below ground as well? Re: Wall cracks, building footpath as per CSIRO BTF18 45Jan 07, 2023 7:29 pm groundzero Lisa06 groundzero Do you know how deep the clays on the west side? Geotech report states approx 500mm fill and 500-1800mm clay Should be class "P". If you want to put in a cut off drain/agi drain then it should go down to 500-600mm deep into the natural clay if there is moisture seeping through the sub surface soil. Do you think the moisture is coming from the surface only or below ground as well? Our soil report states H2/P. So I guess it's both? Do you mean that at the end of the builders plastic the agi pipe would have to drop 600-600mm into the clay? The moisture is coming from below ground as well. There were 3 significant leaks found in our stormwater line. When they identified them, they found that the stormwater trenches were all soaked. We have been told to hold off building any paths around the house until the ground dries completely. But we are having our land graded, so we figured we could at least grade the 1st metre away from the house as a starting point. Re: Wall cracks, building footpath as per CSIRO BTF18 47Jan 07, 2023 8:02 pm That looks brilliant and it makes perfect sense, but I wonder how much something like that will cost us? Does the crushed rock above the agi pipe have to remain crushed rock at the surface? ie. can it be covered with soil/lawn at ground level? Re: Wall cracks, building footpath as per CSIRO BTF18 48Jan 07, 2023 8:37 pm Write reply. If you do the plastic correctly then you can use a narrow trench shovel and backfill the trench will soil maybe add some sand or gravels into the backfill. This would be the cheapest option and maybe you could do it yourself to save money. Just remember that you need the water collecting at the bottom of the trench to discharge somewhere maybe near some trees that should absorb the excess water. .. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Re: Wall cracks, building footpath as per CSIRO BTF18 49Jan 08, 2023 6:40 am groundzero Write reply. If you do the plastic correctly then you can use a narrow trench shovel and backfill the trench will soil maybe add some sand or gravels into the backfill. This would be the cheapest option and maybe you could do it yourself to save money. Just remember that you need the water collecting at the bottom of the trench to discharge somewhere maybe near some trees that should absorb the excess water. .. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Great diagram - thank you. So are you saying the trench could be backfilled with soil (+ sand/gravel) and we could omit the agi pipe? How would we get the water to discharge somewhere without an agi pipe? Also, is there really a need to dig the trench to the clay level (approx 500mm deep)? Won’t surface and subsurface flow automatically work its way through the filled section and settle onto the clay? If surface and subsurface water falls to a depth of 500mm underground and pools a little, are we really likely to notice any damp/soft areas on the ground surface? (if we don't discharge the water somewhere). Lastly, the set up you shared in the diagram above - would that only be necessary on the West side where the land is tipping toward the house? Or would it need to be done all the way around the house? I feel it would only be necessary on the West side. Below is a rough sketch of our property: https://drive.google.com/file/d/1lR0XpwbKvwEAu-lERg5iD6BiHXBO73Uv/view?usp=share_link The red arrows indicate the slope of the land. The blue starred areas (on West side of house and shed) are the areas where the land naturally falls toward the house and shed. These are the problem areas we need to deal with. The South side of the house has a concrete patio so it's not an issue (in terms of water going under the house). The land on the East side of the house falls away from the house (and toward the shed). The North side of the house falls toward the front of the property. So the real issue is the West side of the house. The shed is our second issue. Water hits the shed on the West side (due to natural slope of the land). Water on the North and East sides of the shed falls away from the shed. Water on the South side of the shed is a bit of an issue. On the South side of the shed we have two water tanks enclosed in sleepers and a compacted crusher dust base. Surface water that gets trapped in the sleeper box and also water from the natural fall of the land is moving under the shed (there is a slotted pipe under the tanks to drain some water and this pipe always has water coming from it). We know this as we see water coming out from under the shed slab on the North side of it. Perhaps we just need a massive trench all along the West side of the shed that extends past the water tanks and then we could add an agi pipe that discharges into a spoon drain on the East side of our property. Re: Wall cracks, building footpath as per CSIRO BTF18 50Jan 08, 2023 7:56 am Lisa06 groundzero Write reply. If you do the plastic correctly then you can use a narrow trench shovel and backfill the trench will soil maybe add some sand or gravels into the backfill. This would be the cheapest option and maybe you could do it yourself to save money. Just remember that you need the water collecting at the bottom of the trench to discharge somewhere maybe near some trees that should absorb the excess water. .. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Great diagram - thank you. So are you saying the trench could be backfilled with soil (+ sand/gravel) and we could omit the agi pipe? How would we get the water to discharge somewhere without an agi pipe? As Long as the plastic membrane and trench is done correctly then you can replace the agi pipe with sand or gravels. Also, is there really a need to dig the trench to the clay level (approx 500mm deep)? Won’t surface and subsurface flow automatically work its way through the filled section and settle onto the clay? Yes because then it will flow under your house and can wet up the soil close to the surface under your house.The point of a cut off drain is to stop the water completely and divert it away.This needs to be into the natural clay layer otherwise water will just flow across the top of the natural clay going under your house.The trench that is dig into the natural clay needs to slope away from your house. This can be a problem as you may need to grade the depth of the trench to allow the collected water to flow away. You can end up with a deep trench because of this. The main slope is from west to east but you said there is a slope to the north (front of the property) so you may be able to use the north slope to allow the collected water to flow away without making an artificial deepened trench slope.If this is the case then the trench won't need to be deeper than say 100mm into the natural clay. If surface and subsurface water falls to a depth of 500mm underground and pools a little, are we really likely to notice any damp/soft areas on the ground surface? (if we don't discharge the water somewhere). Yes depending on the amount of water, slope etc. In some situations you can tell there is a broken stormwater pipe because the surface ground is soft and in others no one realised there was a broken pipe until a plumbing camera inspection was done.You may be able to do this in stages so the first step would be protecting the house with the cut off drain and then discharging close by seeing if the subsurface discharge is manageable (ground is not soft and saturated). If it is not working then you may have to extend the trench further away preferable towards trees and bushes. Lastly, the set up you shared in the diagram above - would that only be necessary on the West side where the land is tipping toward the house? Or would it need to be done all the way around the house? I feel it would only be necessary on the West side. Yes in general you only need to protect the high side of the sloping land and the natural slope will move the water away from east side of your house. Below is a rough sketch of our property: https://drive.google.com/file/d/1lR0XpwbKvwEAu-lERg5iD6BiHXBO73Uv/view?usp=share_link I can't get this link to work ! The red arrows indicate the slope of the land. The blue starred areas (on West side of house and shed) are the areas where the land naturally falls toward the house and shed. These are the problem areas we need to deal with. The South side of the house has a concrete patio so it's not an issue (in terms of water going under the house). The land on the East side of the house falls away from the house (and toward the shed). The North side of the house falls toward the front of the property. So the real issue is the West side of the house. The shed is our second issue. Water hits the shed on the West side (due to natural slope of the land). Water on the North and East sides of the shed falls away from the shed. Water on the South side of the shed is a bit of an issue. On the South side of the shed we have two water tanks enclosed in sleepers and a compacted crusher dust base. Surface water that gets trapped in the sleeper box and also water from the natural fall of the land is moving under the shed (there is a slotted pipe under the tanks to drain some water and this pipe always has water coming from it). We know this as we see water coming out from under the shed slab on the North side of it. Perhaps we just need a massive trench all along the West side of the shed that extends past the water tanks and then we could add an agi pipe that discharges into a spoon drain on the East side of our property. Re: Wall cracks, building footpath as per CSIRO BTF18 51Jan 08, 2023 8:20 am groundzero Lisa06 groundzero Write reply. If you do the plastic correctly then you can use a narrow trench shovel and backfill the trench will soil maybe add some sand or gravels into the backfill. This would be the cheapest option and maybe you could do it yourself to save money. Just remember that you need the water collecting at the bottom of the trench to discharge somewhere maybe near some trees that should absorb the excess water. .. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Great diagram - thank you. So are you saying the trench could be backfilled with soil (+ sand/gravel) and we could omit the agi pipe? How would we get the water to discharge somewhere without an agi pipe? As Long as the plastic membrane and trench is done correctly then you can replace the agi pipe with sand or gravels. Also, is there really a need to dig the trench to the clay level (approx 500mm deep)? Won’t surface and subsurface flow automatically work its way through the filled section and settle onto the clay? Yes because then it will flow under your house and can wet up the soil close to the surface under your house.The point of a cut off drain is to stop the water completely and divert it away.This needs to be into the natural clay layer otherwise water will just flow across the top of the natural clay going under your house.The trench that is dig into the natural clay needs to slope away from your house. This can be a problem as you may need to grade the depth of the trench to allow the collected water to flow away. You can end up with a deep trench because of this. The main slope is from west to east but you said there is a slope to the north (front of the property) so you may be able to use the north slope to allow the collected water to flow away without making an artificial deepened trench slope.If this is the case then the trench won't need to be deeper than say 100mm into the natural clay. If surface and subsurface water falls to a depth of 500mm underground and pools a little, are we really likely to notice any damp/soft areas on the ground surface? (if we don't discharge the water somewhere). Yes depending on the amount of water, slope etc. In some situations you can tell there is a broken stormwater pipe because the surface ground is soft and in others no one realised there was a broken pipe until a plumbing camera inspection was done.You may be able to do this in stages so the first step would be protecting the house with the cut off drain and then discharging close by seeing if the subsurface discharge is manageable (ground is not soft and saturated). If it is not working then you may have to extend the trench further away preferable towards trees and bushes. Lastly, the set up you shared in the diagram above - would that only be necessary on the West side where the land is tipping toward the house? Or would it need to be done all the way around the house? I feel it would only be necessary on the West side. Yes in general you only need to protect the high side of the sloping land and the natural slope will move the water away from east side of your house. Below is a rough sketch of our property: https://drive.google.com/file/d/1lR0XpwbKvwEAu-lERg5iD6BiHXBO73Uv/view?usp=share_link I can't get this link to work ! The red arrows indicate the slope of the land. The blue starred areas (on West side of house and shed) are the areas where the land naturally falls toward the house and shed. These are the problem areas we need to deal with. The South side of the house has a concrete patio so it's not an issue (in terms of water going under the house). The land on the East side of the house falls away from the house (and toward the shed). The North side of the house falls toward the front of the property. So the real issue is the West side of the house. The shed is our second issue. Water hits the shed on the West side (due to natural slope of the land). Water on the North and East sides of the shed falls away from the shed. Water on the South side of the shed is a bit of an issue. On the South side of the shed we have two water tanks enclosed in sleepers and a compacted crusher dust base. Surface water that gets trapped in the sleeper box and also water from the natural fall of the land is moving under the shed (there is a slotted pipe under the tanks to drain some water and this pipe always has water coming from it). We know this as we see water coming out from under the shed slab on the North side of it. Perhaps we just need a massive trench all along the West side of the shed that extends past the water tanks and then we could add an agi pipe that discharges into a spoon drain on the East side of our property. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ I’m sorry the link doesn’t work - I just double checked it and it should work. I’ll try uploading a picture. Thanks so much for that very helpful information. It makes sense. Yes, I was going to ask if the trench we dig needs to slope away from the house. It makes sense that it does. Yes, there is also a bit of a slope to the North of the property (we are getting all the land around the house graded, so we will get them to create a good fall away from the house in the North). So does that mean that we would slope the trench on the West toward the North? And then the water should just continue moving to the North? There is a brick fence on either side of the house that extends almost the entire width of the block. This presents a challenge as any trench on the West of the house would essentially need to go under this fence if we slope it to the North. I guess another option could be to make a trench on the West side of the house and then continue sloping it some distance to the West into our animal paddock and letting it discharge there. This animal paddock currently holds a lot of water that's coming from our neighbour, so we will likely have to create some sort of spoon drain/trench along our neighbour's fence line to stop their water coming onto our property. Re: Wall cracks, building footpath as per CSIRO BTF18 52Jan 08, 2023 1:08 pm Write reply...This could be one option without connecting to the stormwater system. You could angle the animal paddock cut off drain so you don't need to deepen the trench as it will run the collected water away. If you use agi pipes and and connect it to the stormwater system via a pit then you won't need the cut off drain in the paddock and the extended angled section on each one. This probably isn't the solutions as I would need to see the site and gather a lot more information but it may give you some ideas how you can adopt these methods to suit your site. Is all the roofing, including the shed connected to the stormwater system or does it damp water onto the ground ? Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ it Re: Wall cracks, building footpath as per CSIRO BTF18 53Jan 08, 2023 4:54 pm groundzero Write reply...This could be one option without connecting to the stormwater system. You could angle the animal paddock cut off drain so you don't need to deepen the trench as it will run the collected water away. If you use agi pipes and and connect it to the stormwater system via a pit then you won't need the cut off drain in the paddock and the extended angled section on each one. This probably isn't the solutions as I would need to see the site and gather a lot more information but it may give you some ideas how you can adopt these methods to suit your site. Is all the roofing, including the shed connected to the stormwater system or does it damp water onto the ground ? Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ it That diagram is very helpful - thank you. I don’t understand what the cutoff drain in the animal paddock is for? Is that to stop the neighbour’s water from approaching the house? We were thinking of running a spoon drain along our entire Western fence line to stop the neighbour’s water coming into our property. Do you think that’s worthwhile? And if we did that, would the cutoff drain in the animal paddock still be necessary? We have a charged stormwater line. The water off the house roof feeds into our water tanks. As does the water off the shed roof. The only area on our property that currently holds a lot of water it the animal paddock. Re: Wall cracks, building footpath as per CSIRO BTF18 54Jan 08, 2023 5:09 pm It is to take the majority of the water and direct it North away from the house before the brick wall blocks that area off. Then the cut off drain at the rear of the west of the house catches less and discharges less to the south which would make the ground there less boggy or not boggy. A spoon drain will not catch the subsurface water. You can test this by digging a hole at the west of your house and seeing if it is wet and starts to collect water do this during a wet period. Remember to go down to at least the start of the natural clay.If there isn't any then you can deal with the surface water only. Is the animal paddock yours or your neighbours? Re: Wall cracks, building footpath as per CSIRO BTF18 55Jan 08, 2023 5:50 pm groundzero It is to take the majority of the water and direct it North away from the house before the brick wall blocks that area off. Then the cut off drain at the rear of the west of the house catches less and discharges less to the south which would make the ground there less boggy or not boggy. A spoon drain will not catch the subsurface water. You can test this by digging a hole at the west of your house and seeing if it is wet and starts to collect water do this during a wet period. Remember to go down to at least the start of the natural clay.If there isn't any then you can deal with the surface water only. Is the animal paddock yours or your neighbours? That makes sense - thank you. The animal paddock is ours. It's about 30m wide, so that's roughly the distance between the neighbour's fenceline and our house. I will carry out the test you recommended when it rains. I think we are getting surface and subsurface water from our neighbour. We literally have a swimming pool in our animal paddock when it rains. The ground takes forever to dry. Is a cutoff drain a better option than a spoon drain (along the neighbour's fence line) then? The animal paddock is all clay so we shouldn't have to dig it that deep, right? Re: Wall cracks, building footpath as per CSIRO BTF18 56Jan 08, 2023 6:03 pm I cut off drain near your neighbours fence line would be better than a spoon drain as a cut off drain can do both surface and subsurface. You need to see the soil profile, is it fill over natural clay of is it natural topsoil over natural clay? Your neighbour may be discharging stormwater onto the ground or there may be a overflowing pool/dam.Finding the source of the excess water would be a good idea and maybe the best option and not cost you anything depending on how you get on with your neighbour. If that doesn't work then a cut off drain near the fence line may be the best option especially if you can't hook up to your stormwater system. Dig out the soil profile then you can work out how deep you need to go with the cut off drain if you can't find the source. Re: Wall cracks, building footpath as per CSIRO BTF18 57Jan 08, 2023 10:40 pm Interesting discussion. To begin with, I would never put my footings into reactive clay. Why not to simply replace clay with 30 cm of compacted sand or low aggregate gravel over geotextile and with proper perimeter agg drainage. You need to replace your building envelope + 1 meter in each direction. Obviously, you would need to prepare your building envelope slightly sloping towards the drainage when excavating. Then concrete apron will be just an optional/good to have thing and you would have the best possible protection and foundation for your footings. As advanced option I would be also looking into something like EZ-Drain in order to save costs on gravel. https://www.ndspro.com/products/drainag ... drain.html Re: Wall cracks, building footpath as per CSIRO BTF18 58Jan 09, 2023 7:57 pm This is an existing house so Lisa06 has to deal with an existing drainage issue and not a new construction situation. 30cm isn't a great deal to reduce the reactivity profile eg West of Melbourne climate category 4 has potential ground movement down to 2.4m.But the less reactive soil the better and what you say about perimeter pavement, grading the soil away from the slab and agg pipe would probably solve must drainage situations and slab heave. Conventional raft slabs often have edge beams down to 300-400mm below ground level in reactive soils but this is different with waffle slabs. Re: Wall cracks, building footpath as per CSIRO BTF18 59Jan 10, 2023 7:41 pm groundzero I cut off drain near your neighbours fence line would be better than a spoon drain as a cut off drain can do both surface and subsurface. You need to see the soil profile, is it fill over natural clay of is it natural topsoil over natural clay? Your neighbour may be discharging stormwater onto the ground or there may be a overflowing pool/dam.Finding the source of the excess water would be a good idea and maybe the best option and not cost you anything depending on how you get on with your neighbour. If that doesn't work then a cut off drain near the fence line may be the best option especially if you can't hook up to your stormwater system. Dig out the soil profile then you can work out how deep you need to go with the cut off drain if you can't find the source. I agree that a cutoff drain would be better than a spoon drain near our neighbour’s fence line. What is the difference between fill versus natural topsoil over natural clay? A neighbour told us that when the area was just vacant land, they added piles of topsoil over it, so my guess is that it’s fill over natural clay. How can we tell? Our neighbour doesn’t appear to be discharging stormwater onto the ground. He has water tanks close to our fence line, and his overflow seems to go somewhere underground (not sure where though). He also doesn’t have an overflowing dam. When it rains a lot here, there is a lot of surface water. Even our neighbour’s land holds various pools of water. He has built his land up higher than ours though, so any surface water falls into our property. When you say “dig out the soil profile” - what exactly do you mean? I’m happy to dig, but I’m not sure what I’m looking for. I guess it would be obvious when I hit clay. Re: Wall cracks, building footpath as per CSIRO BTF18 60Jan 10, 2023 7:44 pm alexp79 Interesting discussion. To begin with, I would never put my footings into reactive clay. Why not to simply replace clay with 30 cm of compacted sand or low aggregate gravel over geotextile and with proper perimeter agg drainage. You need to replace your building envelope + 1 meter in each direction. Obviously, you would need to prepare your building envelope slightly sloping towards the drainage when excavating. Then concrete apron will be just an optional/good to have thing and you would have the best possible protection and foundation for your footings. As advanced option I would be also looking into something like EZ-Drain in order to save costs on gravel. https://www.ndspro.com/products/drainag ... drain.html If we had built this house, we would have done things very differently. But we are the second owners, and we're just trying to do our best with a bad situation. 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