Drainage issue down one side of house

a) anything, no need to buy an end stop or bung or anything just a large stone that blocks it a bit. it certainly doesn't need to be watertight.

b) connect into your gully/ pipe with a proper sewer fitting, i.e. a y or straight connector depending on how its arranged.

c) you want to surround the pipe with at least 4 inches of clean stone. If you are using a mini digger a 9icnh trench bucket will be enough for all but really big projects. More depth of stone on top obviously depending on how deep you are going.
 
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Just watched "Help! my house is falling down" on channel 4 tonight. The couple had a problem with trees absorbing water from their house. It caused the land at the house to shrivel up with height of land reducing by a few inches. This caused the foundations of the house to sink with the lowering of the land.

They gave a warning saying that if too much water is "sucked" from land it can affect the foundations of a house.

I have read about this on a couple of websites that perforated drains can "work too well" and can create subsidence issues.

Should I be worried or look into this more?
 
It's not really relevant on your scale you certainly don't need to worry about it.

You are effectively draining excess groundwater which gradually makes it's way into your trenches, this is very different from the strong active sucking that certain trees specialize in.

P.S Are you ever going to get around to doing this drainage?
 
That's a good question r896neo, I am wondering that myself.

I had a tradesman in yesterday who cut holes in all the rooms downstairs where I am getting the odour from (as mentioned in original post). He said he had a good look and there is nothing wrong with the solum of the house.

The thing I can't understand is the extension part of the house which was built 5 years ago smells absolutely fine - I have deliberately kept the windows closed for 3 days in the extension and it's still lovely. I only have to close the windows in original part of the house for an hour and the foosty smell comes back to the ground floor rooms (top storey rooms all fine).

I had a good look round the side of the house and noticed that the extension has these
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five bricks up from the ground (about 50cm) then every 3-5 bricks along the whole perimeter, giving a total of 13 of them in an extension about the size of a garage.

I noticed that the main part of the house has none of these down the side of the house where the drainage issue is and a couple of them above all the windows - is this right? I understand that these things vent the cavity. Is it possible that the reason why the extension smells fine is because the cavity is so well vented?
 
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MoonMan2 said:
I noticed that the main part of the house has none of these down the side of the house where the drainage issue is and a couple of them above all the windows - is this right? I understand that these things vent the cavity. Is it possible that the reason why the extension smells fine is because the cavity is so well vented?
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They vent the cavity and can act as weep holes, depending on where they are fitted.

Perhaps the extension is timber frame as opposed to traditional build for the main house which might explain the difference. Or maybe the house was built before the vents were a requirement with the extension more recent?
 
Just to give you guys an update.

The landscaper is coming out this long weekend to do the job.

I have another couple of questions. With respect to the trench I dug down the side of the house, which is around 55cm away from house.

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He said he will simply dig the trench deeper and lay the perforated drain there. I am concerned that the trench will be too near the house. Is there a recommended minimum distance that drainage trenches should be from a house?

Don't want the foundations of house to be affected.

Next question, the landscaper said he is going to put drainage gravel down trench, place pipe, cover with some more gravel, then cover with layer of landscaping fabric and top soil before placing turfed lawn on top. Is not necessary for the landscaping fabric to line the trench?
 
Right I have another question in furtherance to above - answers to them would be appreciated.

I have read that the minimum gradient/slope for a french/perforated drain to function correctly is 1%.

What is the MAXIMUM recommnended slope for french drain so that it will function correctly?
 
No need to worry about your foundations as he won't be going that deep.

As for the fabric on high spec drainage for pitches etc the pipe and gravel would normally be enveloped in terram but for a small scale garden project like yours it's a bit OTT in my opinion. But it's your choice so i am sure he would be willing to fully wrap it if you buy the extra fabric.

Lastly falls with land drains don't really work the same as with normal drainage and realistically you can have anything between a tiny 1:100 right up to 1:1. The water doesn't so much flow along it as seep/ trickle.

In some situations you can have vertical french drains down the back of retaining walls.
 
Thanks r896neo, he is going to Y connect into the rain downpipe at the U bend (between rodding point and vertical downpipe) which is 75cm below ground level (he evacuated yesterday).


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My concern is that if the gradient is too steep the water will not have enough 'time' to get into the french drain. So am worried that this water that doesn't manage to get into the pipe will simply flow down the trench, NOT get into y connector/rain downpipe and create a build up of water next to my house.

I am wanting to suggest to him to break into downpipe say at 45cm below ground level, as the maximum run of french drains I will have is 17m. This will allow for a shallower gradient for the entire run, thus increasing water collected into drain??? My two ideas for doing this are:

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Sawing pipe and inserting y connector a bit further up.


OR

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Using two 87.5 degree bends, this has the advantage in that these two pipes can be rotated from the y-connector joint to get the desired depth of discharge for end of french drain.

It just seems a bit extreme to be 75cm below ground for a small garden.
 
Water will always find its own level, and take the path of least resistance. It wont build up if there's an easier route to take, i.e. into the drain.
 
I'm not sure i understand. The gradient has absolutely no bearing on how effective the land drain is at collecting water??

As for your concern about water gushing down a steep slope and missing the y into the drainage system, whilst i understand your thinking and agree that it's a valid point the rate and volume of water coming through the pipe is not really flowing. water enters a land drain almost like uncovering a spring, it sort of floods up into it until it has enough volume to start running away. At no point is the pipe ever flowing like a conventional drainage system and as a result where it joins the y connector the same thing happens, any water that doesn't run straight in simply rises into the space rather than trying to push its way on down through the ground.

Of course you need to make a definate end to the channel as it connects into the y and this can sometimes simply be done with lumps of clay moulded and beaten in around the y or if the soil is not up to that a small plug of concrete.

It sounds like your landscaper knows what he is doing so i would be happy to trust his judgement cause he is there in the trench rather than me or someone else on the forum.
 
r896neo said:
water enters a land drain almost like uncovering a spring, it sort of floods up into it until it has enough volume to start running away....as a result where it joins the y connector the same thing happens, any water that doesn't run straight in simply rises into the space rather than trying to push its way on down through the ground.
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Very nicely explained. I was on the phone to landscaper for 45 mins this evening, he virtually mirrored everything you said r896neo

I think I am driving him mental too.... :rolleyes:
 
Thats the job done. It took the landscaper 3 days, in fact he had to get someone to help him for the last two days. But he finished it just as it was getting dark last night. At the worst point, my garden looked like a building site - what a stressful weekend.

All the stuff I have learned about drainage over the past month made me watch him almost every step of the way asking questions and generally being annoying - I don't think he likes me.

He dug the trenches, placed perforated pipe then drainage chips, a layer of terram, top soil and then turf. It did bother me a bit that he placed the perforated pipe at the bottom of the trenches with no lining/enveloping of terram or chips. I know r896neo said this was not necessary on a small scale. However I do worry that over the years sediment will gather/run in the pipes and eventually either clogg them or even worse clogg the rain water drainage that they connected to. :(
 
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