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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Hardcore and the theory of drainage
Apologies for the uninspiring subject line, but it does at least sum up my
question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? |
#2
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Hardcore and the theory of drainage
In message , Bert
Coules writes Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? Tradition? Probably functions fine if you use the membrane from your earlier post to segregate soil from rubble. You can purchase proper geo-membrane designed for this purpose. Maybe the rubble is to provide a storage void like a soakaway to gain time and to distribute local wetspots? -- Tim Lamb |
#3
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Hardcore and the theory of drainage
In article , Bert
Coules writes Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? I agree with you and I made the mistake in the past of making a shallow soakaway with 40 odd mm hardcore without making sure that soil couldn't migrate into it resulting in a dam rather than soakaway. Hardcore is cheap however so if you buffer it from the soil then I think you would be ok. This could be hardcore then pea shingle on top then a soil blocking membrane. A full fill of pea shingle might be better (again with membrane). While I'm sure you do want free drainage, I'm also pretty sure you don't want the beds to dry out too much either so there must be some kind of balance to be had (IANAG). -- fred it's a ba-na-na . . . . |
#4
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Hardcore and the theory of drainage
On 22/11/2014 09:28, Tim Lamb wrote:
In message , Bert Coules writes Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? Tradition? Probably functions fine if you use the membrane from your earlier post to segregate soil from rubble. You can purchase proper geo-membrane designed for this purpose. Maybe the rubble is to provide a storage void like a soakaway to gain time and to distribute local wetspots? I don't think it is an uninspiring (or silly) question at all, I have pondered the same thing in the context of stable yards (Type 1 on top of hardcore) and also preventing field gateways from getting muddy in the winter. For flower beds I think it is largely the gaps that matter, not the porosity of the bricks etc. in the same way that shingle or gravel is good for trenches over land drains as well as soakaways. I agree with Tim that a membrane between the soil and the hardcore (or gravel) is necessary to slow down the rate of transport of fine material which would fill the gaps. If your "bare earth" is impermeable or tends to get saturated you might want "weep gaps" in the block wall to help drain the hardcore zone, otherwise the raised bed might fill up like a bucket. If you have never come across it, the PavingExpert website is a mine of useful information on more than paving. |
#5
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Hardcore and the theory of drainage
On Saturday, November 22, 2014 10:11:57 AM UTC, fred wrote:
In article , Bert Coules writes Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? I agree with you and I made the mistake in the past of making a shallow soakaway with 40 odd mm hardcore without making sure that soil couldn't migrate into it resulting in a dam rather than soakaway. Hardcore is cheap however so if you buffer it from the soil then I think you would be ok. This could be hardcore then pea shingle on top then a soil blocking membrane. A full fill of pea shingle might be better (again with membrane). While I'm sure you do want free drainage, I'm also pretty sure you don't want the beds to dry out too much either so there must be some kind of balance to be had (IANAG). The soil will be drier than the ground level garden simply because its raised. I wouldnt expect a wetness problem, thus no need for a solution. The rest of the ground doesnt need a hardcore & membrane layer, so why does the raised bed? Weep holes in the sides avoid a lot of extra load, plus shed heavy downpours quicker. NT |
#6
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Hardcore and the theory of drainage
On 22/11/2014 08:36, Bert Coules wrote:
Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". Will you need any drainage for a raised bed of this height? Will it ever become waterlogged? More likely it will be a lot drier than planting at ground level. In the summer when you want more water a heavy rainfall is unlikely to wet the soil by more than a few inches below the surface. -- mailto: news {at} admac {dot] myzen {dot} co {dot} uk |
#7
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Hardcore and the theory of drainage
On 22/11/14 08:36, Bert Coules wrote:
Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? limestone itself and to an extent brick will be permeable, and if you mix with sand, the thing will not clog up with fine sand and clay. I wouldn't worry too much, but do out drainage hoes in the base to avoid waterlogging. What the hardcore does for a decent time is to provide a space where water can pool. thus relieving the soil above from total waterlogging. -- Everything you read in newspapers is absolutely true, except for the rare story of which you happen to have first-hand knowledge. €“ Erwin Knoll |
#8
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Hardcore and the theory of drainage
Thanks to everyone for the replies. As usual with this sort of area, the
range of advice is extensive. I have a source of old concrete panels which I can break up and use for hardcore, but I'll have to bring in some smaller aggregate to use as a filler material and to level off the top of the base layer - without that, I suspect that any membrane, even the toughest, would be penetrated by the edges of the concrete shards. I've also been told that broken-up chunks of expanded polystyrene made a good substitute for traditional hardcore (and would certainly be easier to handle) but, as with something harder, I'm still not sure I completely understand the way the drainage is supposed to work. However, any moderately sizeable material would at least cut down on the amount of smaller infill necessary, which I suppose would be a saving. Newshound, particular thanks for the link to the Paving Expert site: what a splendid resource. Bert |
#9
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Hardcore and the theory of drainage
Bert Coules wrote:
I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". You might find that during summer the block walls will cause a loss of water by evaporation through them; and a bed raised this high might well have plenty of natural drainage anyway. You could well have more of a drying out too fast problem rather than a too much water one. I suggest you ask for comments in uk.rec.gardening. -- Terry Fields |
#10
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Hardcore and the theory of drainage
On 22/11/2014 17:38, Terry Fields wrote:
Bert Coules wrote: I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". You might find that during summer the block walls will cause a loss of water by evaporation through them; and a bed raised this high might well have plenty of natural drainage anyway. You could well have more of a drying out too fast problem rather than a too much water one. I suggest you ask for comments in uk.rec.gardening. If your bed faces S/SW (prevailing weather) it will probably need good drainage. I have a north facing bed that is almost always on the dry side. I'm a great fan of vermiculite which, when mixed 1-6 with soil retains water (and air) but is also self regulating drainage wise. A 20L bag was about a tenner last time I looked |
#11
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Hardcore and the theory of drainage
"Bert Coules" wrote in message o.uk... Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? Water in the upper soil layer drains into the hardcore The voids in the hardcore acts as a store for water in heavy rain. The water seeps away later nto the ground under the hardcore. So the top lay neverg ets waterlogged. Best if you put a porous membrane on top of the hard core to stop the soil washing into it. Old bulk bags cut up are ideal. |
#12
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Hardcore and the theory of drainage
"harryagain" wrote:
The voids in the hardcore acts as a store for water in heavy rain... Best if you put a porous membrane on top of the hard core to stop the soil washing into it. If there are appreciable voids in the hardcore, won't the weight of the topsoil onto the membrane cause it to be punctured on the hard edges? But alternatively, if I try to smooth out the surface of the hardcore (say by pouring on a smaller aggregate) won't that just sink down and fill the voids, severely limiting the drainage? |
#13
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Hardcore and the theory of drainage
Stuart Noble wrote:
I'm a great fan of vermiculite which, when mixed 1-6 with soil retains water (and air) but is also self regulating drainage wise. Thanks for the suggestion. I'll investigate. |
#14
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Hardcore and the theory of drainage
"Bert Coules" wrote in message ... "harryagain" wrote: The voids in the hardcore acts as a store for water in heavy rain... Best if you put a porous membrane on top of the hard core to stop the soil washing into it. If there are appreciable voids in the hardcore, won't the weight of the topsoil onto the membrane cause it to be punctured on the hard edges? But alternatively, if I try to smooth out the surface of the hardcore (say by pouring on a smaller aggregate) won't that just sink down and fill the voids, severely limiting the drainage? Depends on the nature of the hardcore. Ideally it should be topped off with pebbly stuff (no sharp edges) to protect the membrane. Available as "pea gravel" or "shingle" (dredged from the sea) at builders merchants. In practice any smaller stuff on top doesn't get far into the stuff below and bulk bags are very tough. Depending on the thickness. All depends on how much of a perfectionist you are and what you want to grow. If the soil is light (ie not clay) you might need none of this. Alternative method is just to mix sand in with the soil, you need a lot more than you might think. You may need weep holes in your retaining walls if the soil blow is clay, reduces the forces on them. Also good idea to paint inside of retaining walls with bitousmous paint, stops frost damage and excessive drying out in drought conditions. |
#15
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Hardcore and the theory of drainage
Chris Hogg wrote:
I think you're making a huge meal of this. No doubt. But I enjoy looking into such things and I'm grateful for all the comments and advice. Bert |
#16
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Hardcore and the theory of drainage
On Saturday, 22 November 2014 08:36:43 UTC, Bert Coules wrote:
Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? |
#17
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Hardcore and the theory of drainage
On Saturday, 22 November 2014 08:36:43 UTC, Bert Coules wrote:
Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? |
#18
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Hardcore and the theory of drainage
Nothing from you twice in a row.
Do you always get premature ejaculations ? wrote in message ... On Saturday, 22 November 2014 08:36:43 UTC, Bert Coules wrote: Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? |
#19
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UNBELIEVABLE: It's 02:36 am in Australia and the Senile Ozzietard has been out of Bed and TROLLING for ALMOST EIGHT HOURS already!!!! LOL
On Tue, 18 Feb 2020 08:16:25 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again: FLUSH senile troll**** 08:16??????? ROFTLOL! IOW, you haven't slept ONE MINUTE last night because this here is the ONLY place where you can talk to people without them being able to get away from you, you cantankerous obnoxious auto-contradicting sociopath! LOL -- Norman Wells addressing trolling senile Rodent: "Ah, the voice of scum speaks." MID: |
#21
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Hardcore and the theory of drainage
On Saturday, 22 November 2014 08:36:43 UTC, Bert Coules wrote:
Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? I built 40m of rasid beds at my place .. filled in with 40mm clean stone, all fully wrapped in Terram, then soil on top. At base of stone I also run in French dreain for full length ... open at ends (with mesh guard) water can then drain down through stones into pipe and out. |
#22
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Hardcore and the theory of drainage
On Saturday, 22 November 2014 08:36:43 UTC, Bert Coules wrote:
Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? Works best if you put coarse stuff in the bottom & then successive layers of finer stuff and then a permeable membrane & then you soil. A lot depends on what you want to grow, Some stuff likes it wet. If it's something that likes it dry, mix sand with your soil if it's aclay soil. Leave "weep holes" in the walls of your raised bed or they may collapse with the weight of water. https://en.wikipedia.org/wiki/Weep |
#23
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Hardcore and the theory of drainage
harry wrote:
On Saturday, 22 November 2014 08:36:43 UTC, Bert Coules wrote: Apologies for the uninspiring subject line, but it does at least sum up my question. I'm constructing a large and quite high (thirty inches or so) raised bed in my garden for planting: block walls enclose an area of bare earth at ground level. The bed will be topped by a layer of soil, and I've been advised to put in a bottom layer of hardcore "to assist drainage". What I don't quite understand is how a layer of rubble, broken-up bricks and the like can have anything to do with drainage. If the spaces between the bits remained clear and open, yes I can see that: but surely the soil (or whatever I use as a "middle" layer) will simply fill those gaps? OK, water will drain down through that material - but it seems to me that it would do so even better and faster if the hardcore wasn't there, getting in the way. Or is the hardcore itself, rather than the spaces between the pieces, more permeable than I realise? Works best if you put coarse stuff in the bottom & then successive layers of finer stuff and then a permeable membrane & then you soil. A lot depends on what you want to grow, Some stuff likes it wet. If it's something that likes it dry, mix sand with your soil if it's aclay soil. Leave "weep holes" in the walls of your raised bed or they may collapse with the weight of water. https://en.wikipedia.org/wiki/Weep Dont you think that after 5 year Bert might have dealt with and/or lost interest in the issue? Youre getting as daft as those poor souls over in HOH. Tim -- Please don't feed the trolls |
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