Path drainage - what angle

[johnboi]

After using your website last year and making such a good job of laying a patio I am lumbered with laying a path.

Her indoors wants a path that will snake down the garden against my protestaions that a straight one would be easier!!

Anyway it will be 720mm wide and around 20 metres long.Using Marshalls chapelgate red multi clay pavers

I understand about setting the edges in morter but it is the drainage that most concerns me.

First is it necessary and if so how do I do it?

I'm thinking that I could have one side of the path higher than the other so it is at a slight incline.Would this be better than having it higher at the start and lower at the bottom.

If so what sort of incline should I have for a path of that width?

Thanks for your help

Keep up the good work this website is an invaluable source of information long may it prosper.

[johnboi]

Ok I guess this question is either too hard or too simple for anybody to bother answering.

Unless I haven't phrased it right.And the question is not understood?

So I'll give it another go.

A path 720 mm wide snaking down the garden for 20 metres.I am using clay pavers 3 in the centre laid flat on sand and at the edges on their side set in mortar as edgings.Cut to need.

Do I need to bother with drainage or will it be just ok flat?

If I have a slope across the path ie from one side to the other rather than from one end to the other end say 20mm slope will this provide the drainage so I don't get puddles.Is that slope too steep and be noticeable?

Thank you in anticipation of an answer.

John

[84-1093879891]

Bloody hell! Give us a chance! I spent 3 hours yesterday answering posts to the Brew Cabin, plus over 10 hours ploughing through emails and dealing with 'phone calls - there are limits to what I can do, you know!

Lay the path to a slight camber so that surface water is shed to either side. At 720mm wide, the centre need be only 15mm or so higher than the edges and it will be fine.

[johnboi]

Sorry Tony

Didn't mean to hassle you!

I was getting earache form she who must be obeyed who wants this path building pronto!.

Never thought about doing it like that so how do I do it.

Do I stick a peg in the centre so I can get a higher level?

How would I screed this?

I'm sure the answer is simple but I need some direction.

I would appreciate a link if there is one on how to do this on your website.

This time there is no rush as I can't get the pavers until a week saturday so this time I won't hassle you for an answer.

Thanks again Tony for your reply

Full time job this website then?

Can't tell you how useful it is to me couldn't have done it without you.

cheers

John

[84-1093879891]

Cut a cambered screeder board!

You're planning to lay your edge courses first, so have one edge fixed and one floating, as described on the Edge Courses page. Set the free/floating edge to (width of path + 20mm) to ensure there's ample room to work.

Measure the distance between fixed and floating edge, cut a piece of timber (summat like 75/x50 or 100x25) so that it is roughly 150mm longer than the gap.

Next, cut notches at either end, allowing approx 52mm depth (assuming 60mm deep pavers) and 80mm length. These notches will ride over the top of the edge courses.

Cut the base of the screeder board to a cambered profile, and there you have it....



Prepare your bed as per normal by placing and partially compacting the sand, then drawing the cambered screeder board over it, ensuring the notches stay in contact with the top of the edge courses, and away you go....



Obviously, you could lay the edge courses so that they, too, have a touch of fall and are not actually flat, as shown in these diagrams, but the point is made....



Don't forget to let us know how it turns out. :)

[johnboi]

You are a life saver Tony.

It's easy when you know how isn't it.

The pavars come this weekend I will let you know how I go on.

Once again thank you very much.

John

[johnboi]

Hi Tony

I wonder if you or anyone can offer some advice?

I got round to digging out and laying one edge of my path this weekend and laying a layer of hardcore.

Today we have had a torrential downpour so work has been delayed.

Now some areas of the dug path had puddles these have drained away to leave patches of really wet hardcore like mud which is very soft!!!


I'm concerned how these are going to properly support the finished sand layer and pavers.


What can I do?

Is it something to worry about?

Once the pavers are laid I suppose the water will drain off onto the garden rather than underneath.

Should I wait until these areas are drained and dry before continuing?

Should I lay a bed of concrete around these areas?

Any advice would be a great help

thanks

john-boi

I've managed to cover most of the path with tarpaulin as the rain is coming down again

[LandscapeMann]

John,
IMHO the compacted hardcore ( I asume hardcore is similar to crush and run 3/4" that we use in the US) must be hard not,
"like mud which is very soft!!!" as you described.

Your final surface will only he as stable as the subgrade beneath it.

If the soil is saturated below your hardcore it will cause your hardcore to mush.

In the best of circumstance I prefer the hard core base to have some fall and a place to drain to daylight. I realize that is sometimes difficult to do. As it may raise the final height of your paving/path but may be able to adjust the finished grade to meet that.

I actually had a ton of rain during my last pathway project. And decided to raise the hardcore a couple inches before it got saturated. for the same reason. But I was able to adjuust the finished grade beside the walk to compensate.

As far as what to do in your case. At a minimum I think you should excavate any saturated soil under your hardcore and fill in with as dry hardcore as you can manage. Recompact with a plate compactor. The other thing to consider is what is the nature of your soil. If it is high in organic material/topsoil. it is not suitable as a base under your hardcore. And should be replaced.

As a rule I use my vibratory plate compactor over my subsoil to make sure it is as tight as possible before installing the hardcore.

Sorry, I know this will cause you extra work. But I don't really know of a cheap and easy solution.

I guess you may be able to wait out the wet and see if everthing drys up and tight. With out being there and seeing the conditions, drainage soil types etc. I can not say if that is a satisfactory option.

As far as tarping I have found limited success. Water seems to always find the lowest point. And if one is not there to remove the tarp, it can hold in the moisture keeping the area from drying as quickly.

LM

[johnboi]

Thank you so much for your prompt reply LandscapeMann.

From what you have said I think my problem is that particuarly where it is soft like mud the ground to either side is much higher than the finished path.

I see now that the water will be draining down into the crusher layer of my path.

So from your response I guess what I need to do is to remove the soil surrounding the path so that it is at least level with the finished path.At least then all the water is not going to drain into my path.

Also dig out all the wet sludge and crusher until I get some firmer ground then refill with crusher.



Have I made a mistake in having the finished level of the path at the same height as the lawn?

I can't believe this weather over the weekend I got burnt it was so hot now we have thunder and torrential rain.

At least it has shown me where the problems are better now than after I had laid the path.

If you or anyone else has any furthur advice please help.

thanks again

johnboi

[84-1093879891]

Hardcore is a not a term I like to use - it's too vague and non-defining, and it has a disturbing tendency to attract one-handed surfers to this website. ;)

Hardcore, as I've said before, is a non-specific term used to refer to any 'fill material' from broken bricks, old bits of concrete, cracked flags, right up to top quality, crusher run and sieved primary source material. I'm a great believer in using strict definitions as an aid to understanding, and when I write of 'granular subibase material', I hope everyone knows exactly what I mean, and won't be getting confused into thinking some old bricks they've had stacked at the back of the shed for the last 20 years will do!

So, let's assume that JohnBoi has had the sense to use a proper granular material and that, with the exceptional rain we've had over the last day or so, it's all gone a bit slushy. This happens on every site, and it's really not the end of the world. In many cases it comes about because the sub-grade isn't free-draining, and the sub-base material itself is loose and able to hold a significant quantity of water - hence the slushiness. Left to its own devices, it [i[]will[/i] drain in a day or so and return to more-or-less its former condition. When it's saturated, granular material tends to "suck" on the plate of the compactor, making it almost impossible to get the plate moving again, and it often vibrates a lot of the water to the surface.

The best course of action is to leave it. Give it a day or so and it will probably recover. You might find that those areas that had a generous serving of 'fines' remain slutchy for longer, so it's worth blinding over them with some no-fines material, compacting them into the surface, and then proceed as normal.

If they remain slutchy or soft for more than 24 hours after the end of the rains, then it may be necessary to dig out the soft spots and replace them with new sub-base material. This is more important on those areas that will be subject to vehicular traffic than it is for footways and patios, but always give it 24 hours of dry weather (if poss) before making a decision to dig out.

When a project is at this stage, with the ground open and the paving waiting to be laid, the exposed sub-grade or sub-base is very often lower than the surrounding ground and if you get caught out with the weather, your careful excavation turns into a pond. However, once the water drains away and the path is completed, the permeability of the compacted sub-base, bedding course and the paving itself is often less than that of the adjacent ground, so the water will usually travel to the sub-grade via the adjacent soil area rather than try to fight its way through all those compacted paving layers.

So: for now, allow the slushy areas to dry out, blind them with fresh DTp1, ort dig aout and replace if absolutely necessary, and then crack on as normal. A good shower helps to tighten up a sub-base by washing fines into voids and thereby creating a better structure, so look on this as being a benison, not a problem. :)

For future reference, try to get an area excavated, stoned-up, and paved as quickly as possible. Wet or slushy sub-base material is much less of a problem than wet or slushy sub-grade, which can result in soil-pumping. This is a nasty process that is virtually guaranteed to ruin a pavement, so the key is to get your sub-grade covered with sub-base material as soon as poss.

Next weekend can't be as problematic, weatherwise, can it?? Or am I tempting fate??

[LandscapeMann]

John,
Yes I agree with:
"At least it has shown me where the problems are better now than after I had laid the path."

John said:
"From what you have said I think my problem is that particuarly where it is soft like mud the ground to either side is much higher than the finished path.

I see now that the water will be draining down into the crusher layer of my path. "

Yea, I don't think you want any sections of your path where the grade is much higher on either side than the finished height of the path.



As far as the having the finished grade level with the lawn. I prefer it to be a bit higher than the lawn, so that the water from the walk has a place to drain off.

I know what you mean by burning hot one minute with close to 100% humidity and pouring rain the next. Exactly the same weather pattern that I was wking. in. I have passed the half century mark and the hot whether was kicking my A**.

I think building walks/patios when it is raining heavy is tricky, even for the pros. It can screw you up if it rains at the wrong time.

I am guessing if you get the whole job excavted compacted and layed with no rain. You may be able to get away with walk at the same level as lawn. But you still want to ensure that the water drains off the path.
But when you get all that rain during the job. I found in my case the safer route was to add a couple inches to the hardcore base to make sure it drained correctly. Actually turned out to be the smart thing to do. As that night we had over 2" of rain (50mm). The next day, my base was dry and hard and I was able to proceed with out delay.

Anyway, it sounds to be that you are taking the required action to secure a correct job. But I am just one small voice in the grand scheme of things. If anyone else has any other ideas?

LM

[johnboi]

Thanks to you both for your advice and support it really has helped.

It is a bit daunting to have dug what looked like a perfect path in the sun to see some of it turn to puddles in the rain!!!

Those of you in the UK will know how much rain we have had in the last 2 days.

In Sheffield where I am they reckon at least 3 inches in the last 36 hours and it is still fallling.


The tarpaulin we laid over the path is holding a stream of water.

So it looks like the best course of acton is to wait for the dry weather and hope most of it drains away.

Dig the surrounding areas where possible to lower than the finished path.


Where the crusher layer refuses to drain after a day or 2 to dig that out and replace with more crusher.

I got what was called crusher from Jewsons this though seems to have too much fines (sandy) material than I imagined.

I might be tempted to get a ton of coarser material to place over the more stubborn areas.

The problem with this lawn is that it is very clay like underneath.


Part of the project is to prepare a circular area that is going to be used for seating about 5 square metres.


Would it help the overall drainage of the lawn if we dig this fairly deep (the path will have an overall depth of 160 mm) say 400 mm and fill with coarse material before crusher, sand and pavers to act as some sort of drainage area. Or will this have no affect?

I'm just thinking of things to help the drainage of the lawn so any other suggestions would be appreciated.

Sometimes when we have a heavy downpour the lawn will retain surface water for a few hours in areas once the rain has stopped.So obviously I need to encourage drainage somehow.

I can see from the structure of the lawn now that one edge is higher than the middle and obviously this will send water towards the lowest central point.

I will certainly remove this slope in order to level the surface a bit and maybe make it slightly lower than the centre so at least the water has a chance to drain somewhere else than towards my new path.


Sorry if I have gone on a bit but your input has really helped and makes it feel like I'm not alone in this task which has helped immensely.Without the resources of this website/forum I would have been groping in the dark.

[84-1093879891]

I'm not sure that creating what will be a sump in the area of the circular seating area is a particularly good idea. Properly prepared, there's a reasonable chance that you'd be able to avoid any long-term settlement, but unless it could be shown that this sump would act as a soakaway, I can't see what benefit it brings to the lawn.

A proper land drain construction, laid alongside the path you're building, or at some other convenienmt location, would be the ideal solution, but, as with all land drain schemes, having a suitable outfall is the key to success. Is there a SW drain that could be comandeered for the purpose?

[LandscapeMann]

Tony,
Thank you for the clarification of the "hardcore" term. I need to learn what the comparable base materials are so that I am on the same page.

Your course of action for the water problem sounds like the most prudent.
try the least invasive first.
We must have been typing at the same time.

Kind of a coincedence that we had a simialar recent period of heavy rains messing with our paver projects over on this side of the Big Pond (US) Around the same time as you guys. I guess it might be raining all over the world.
LM

(Edited by LandscapeMann at 6:56 pm on Aug. 11, 2004)

[georgeformby]

By the way it is me johnboi I've had to reregister as george formby!!!the forum just wasn't accepting my old john-boi details!!

Just thought I would let you know how we got on.

Over the weekend we managed to lay the rest of the path.

I lowered one side of the garden so now there is less run off onto one section of the path.

I dug out the muddy areas and allowed to dry and refilled with crusher.

The path looks great but the rain keeps falling which leads me to one little niggle.

If you can imagine the path is like an S and the bottom curve of the S locks some of the surface water in as it can't get through the path.This does eventually drain away and will really only be a problem when we get weather like we have have had over the last couple of weeks.

Ideally I should have put some drainage through the path to allow this water to escape.

My thought is to lower the ground to the left of this curve in order to encourage the water to drain to that side of the garden rather than try and drain thorugh the path to the right.

I think the main problem is that the garden to the left is higher than ours so all his water makes its way into our garden.

I wonder can I construct some sort of drainage channel along the edge of the garden that will take the water to say the bottom of the garden away from the paved area.

Is there such a thing?

I sure that in normal weather it won't be a problem but my worry is that always having this block to water drainage over the longterm may weaken that curve?

Once again thanks to all your help I only wish I had a digital camera then I could send you a picture of the finished thing as my friends don't seem that interested in my path building exploits.Wait until they build one of their own then they will understand!!!