Approved Doc H vs. 150mm for DPC
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MattTaylot
- Posts: 7
- Joined: Fri Apr 12, 2002 10:11 am
hi,
am celebrating the golden jubilee by digging, and digging and...
Can I ask your advice on the drainage, etc.?
I am a bit confused by my reading of Approved Doc H.
According to Diagram 10, in this doc, if I have 150 mm of cover (what do classes B, D, F and N mean? as well as bedding factors 1.1, 1.5 and 1.9?), then I am ok with my rigid pipes.
According to Table 8 though, it seems that I might need 600mm (looking at the fields column - is that what would apply here?).
Although, according to section 2.44, if I used the reinforced concrete slab, etc., I could get away with less.
However, where my foul drain from the toilet starts (and even for some length away from there), I only have about 150mm between the top of the drain pipe and where the top of the finished surface can be so that the finished surface will be no less than 150mm below the dpc.
Which one takes priority? the 150 mm below the dpc or the drain? I gather the drain, but it is still going to be tight, even following section 2.44 of approved doc. H.
How would you solve this problem?
Finally, I have one other question. Using a breaker near where the soil pipe enters the chamber, the seal around the bottom of the soil pipe cracked and a pece of the sealing material came loose (honestly, I was at least 1 ft or so away from it).
There is a gap of about 25-50mm between the bottom of the pipe and the top of the chamber, so when the piece came loose there was a gap.
I have temporarily cemented around this gap to seal it again, but what is the proper non-bodge way to fix this?
Thanks a lot and I hope you're enjoying this weekend more than I am (God, my muscles hurt!!),
Matt
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84-1093879891
Don't get too absorbed by DocH, Matt - it's used to ensure compliance of new build but for minor repairs or small additions to existing systems, it has to be treated as 'good advice' rather than 'strict law'.
The various bedding classes are more to do with soil mechanics and the various types of pipe material but the reasoning behind them would take a day to write out - take it from me that you really don't need to worry yourself about them. :)
If your pipewoirk is beneath a graden, path or patio, then surround it with 100-150mm of pipe-bedding and it should be fine. If it';s beneath a driveway or other trafficked area, then it ought to be concreted in, especially if it's uPVC. Clayware is much stiffer and can look after itself at shallow depths. If you plan to sell up, though, it;s worth iusing marker tape to warn any future occupants of the shallow nature of your new drainage.
Next - the damage to the chamber. If the mortar repair is holding, that will be fine. Under site conditions, we might use a granolithic mortar to repair, or, in some cases, an epoxy 2-part mortar, but for what little damage you seem to have done, a mortar repair should be fine, as long as you've packed in plenty of it into the gap and it's not just a Rizla-thickness skim.
Now - get back into that trench! ;)
The various bedding classes are more to do with soil mechanics and the various types of pipe material but the reasoning behind them would take a day to write out - take it from me that you really don't need to worry yourself about them. :)
If your pipewoirk is beneath a graden, path or patio, then surround it with 100-150mm of pipe-bedding and it should be fine. If it';s beneath a driveway or other trafficked area, then it ought to be concreted in, especially if it's uPVC. Clayware is much stiffer and can look after itself at shallow depths. If you plan to sell up, though, it;s worth iusing marker tape to warn any future occupants of the shallow nature of your new drainage.
Next - the damage to the chamber. If the mortar repair is holding, that will be fine. Under site conditions, we might use a granolithic mortar to repair, or, in some cases, an epoxy 2-part mortar, but for what little damage you seem to have done, a mortar repair should be fine, as long as you've packed in plenty of it into the gap and it's not just a Rizla-thickness skim.
Now - get back into that trench! ;)
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MattTaylot
- Posts: 7
- Joined: Fri Apr 12, 2002 10:11 am
not back in the trench!!!
You have no idea how much I (and my very kind and helpful neighbour) ache!
But I had a real reason for writing besides just moaning. I wanted to clarify what to do where the drain pipe level is so high relative to the dpc.
I think I might have exaggerated a bit (unintentionally) when I wrote before. It's more like 120mm between the top of the pipe and the top of my proposed finished surface.
(I just stretched my legs. You wouldn't believe the technicolour bruise I have on my knee).
I'm the guy who wrote recently) in a different forum about using granite setts (50mm thick). That only leaves about 70mm below the bottom of the setts and the top of the drain pipe.
I'm thinking of a rigid construction (because that's what's used at the place that I saw them and really liked them).
According to your pages on rigid-construction setts, I can get by with just 50 mm of bedding between the bottom of the setts and the top of the sub-grade (clay down here in London -- very heavy clay, my back reminds me). I was going to have the usual 100mm of hardcore as a base in other places, but in this area where I only have 70mm between the bottom of the setts and the top of the pipe could I get away with 50mm of bedding with 20mm of the pipe bedding layer below that?
It is in a back corner of a patio that shouldn't (famous last words) get much traffic at all.
What would you do?
And one final question. There is tons and tons of concrete all around this chamber (for foul) and another gully for surface water, any ideas why? In some areas, it stretches for nearly 6 inches, perpendicular to the pipes themselves? I just don't understand.
thanks again,
Matt
P.S. Yes, I am taking pictures. My neighbour intends to use them to speed through the committment papers. :) But, if I survive this without hernias, insanity, etc., I'll pass them on to you (hopefully not just for the "don't EVER do it like this!!" pages).
You have no idea how much I (and my very kind and helpful neighbour) ache!
But I had a real reason for writing besides just moaning. I wanted to clarify what to do where the drain pipe level is so high relative to the dpc.
I think I might have exaggerated a bit (unintentionally) when I wrote before. It's more like 120mm between the top of the pipe and the top of my proposed finished surface.
(I just stretched my legs. You wouldn't believe the technicolour bruise I have on my knee).
I'm the guy who wrote recently) in a different forum about using granite setts (50mm thick). That only leaves about 70mm below the bottom of the setts and the top of the drain pipe.
I'm thinking of a rigid construction (because that's what's used at the place that I saw them and really liked them).
According to your pages on rigid-construction setts, I can get by with just 50 mm of bedding between the bottom of the setts and the top of the sub-grade (clay down here in London -- very heavy clay, my back reminds me). I was going to have the usual 100mm of hardcore as a base in other places, but in this area where I only have 70mm between the bottom of the setts and the top of the pipe could I get away with 50mm of bedding with 20mm of the pipe bedding layer below that?
It is in a back corner of a patio that shouldn't (famous last words) get much traffic at all.
What would you do?
And one final question. There is tons and tons of concrete all around this chamber (for foul) and another gully for surface water, any ideas why? In some areas, it stretches for nearly 6 inches, perpendicular to the pipes themselves? I just don't understand.
thanks again,
Matt
P.S. Yes, I am taking pictures. My neighbour intends to use them to speed through the committment papers. :) But, if I survive this without hernias, insanity, etc., I'll pass them on to you (hopefully not just for the "don't EVER do it like this!!" pages).
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84-1093879891
Where the pipework is very close to the surface, I'd concrete in the pipework, leaving the top of the concrete at least (depth of setts + 30mm) below paving level. Then, lay a separation membrane over the concrete before placing the concrete bedding for the setts themselves.
This separation membrane could be a layer of 125 micron visqueen, if you have any available, or even old polythene rubble sacks, sand bags ftrom the BM or anything like that. The idea is to prevent the bedding material bonding directly to the pipe haunching so that, if, at some future date, the setts need to be lifted for whatever reason, they are not directly 'stuck' to the pipework and can be removed without affecting the drainage system.
There's no need for a sub-base where the pipe haunching is close to the surface. It can be re-introduced where levels permit, but it's not essential in this one spot.
The very generous concrete around the existing may be for any of a hundred reasons - they may have had loads left over from another job; they may have needed to protect the pipework from heavy loads; there may have been a worry about settlement - who knows? If you try to work out what the groundworkers were thinking when they did every strange thing you come across, you'll end up going mad! ;)
Looking forward to the pics. :)
This separation membrane could be a layer of 125 micron visqueen, if you have any available, or even old polythene rubble sacks, sand bags ftrom the BM or anything like that. The idea is to prevent the bedding material bonding directly to the pipe haunching so that, if, at some future date, the setts need to be lifted for whatever reason, they are not directly 'stuck' to the pipework and can be removed without affecting the drainage system.
There's no need for a sub-base where the pipe haunching is close to the surface. It can be re-introduced where levels permit, but it's not essential in this one spot.
The very generous concrete around the existing may be for any of a hundred reasons - they may have had loads left over from another job; they may have needed to protect the pipework from heavy loads; there may have been a worry about settlement - who knows? If you try to work out what the groundworkers were thinking when they did every strange thing you come across, you'll end up going mad! ;)
Looking forward to the pics. :)