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Green Building Bible, Fourth Edition
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    • CommentAuthormarsaday
    • CommentTimeJun 21st 2017
    My BC guy is on holiday till july, but i am wanting to plan and work out how to get my new drainage system into my new extension and drive.

    I am going to replace all the old drainage and tap into an unused connection at the bottom of the drive. This way i make the shared drain with my semi neighbour redundant. He currently has the outpipe into the sewer on his side and so my drains run under my conservatory (now to be extension), then under his and turns left and goes down his drive.

    So i will be digging in my drive and wanted to know how safe is it to dig next to a house. The current drains are 1.8m away from the house gable end and so i will work along this line as well with new drains. The falls will be in the opposite direction though.

    I think the connection in the drive is about 1100 deep, so i will be working backwards from here. Using a 1:40 fall i will need to come up 150mm every 6m's. The total run for the drains is about 27m.

    So i will be going 1m deep around where the house walls start on the drive, but will be 1.6-1.8m away from the wall.

    My house was built in 1910 so i think the foundation is not going to be that deep. It is laid on a brick rubble spread base i think. Just not sure how actually deep it all is though.

    Any issues i need to think about before all this starts. Are there any good drainage sites i could have a look at to get the knowledge up. I have read some regs and it seems i may need to set the drains in concrete, but i am not sure on this one at the mo.
    • CommentAuthortony
    • CommentTimeJun 21st 2017
    Keep away from a like going at 45 degrees from the bottom of the house foundations by moving further away

    You should be OK, surround drain in pea gravel.
    • CommentTimeJun 21st 2017 edited
    Your neighbour will be grateful to be relieved of 'owning' a shared drain, if he ever wants to build an extension on top of it.

    What used to be a matter of common sense agreement with the building inspector, promptly on site when called to see,
    is now controlled instead by your water board (who acquired responsibility back about 2013, more than doubling their network overnight), treated as if he'd be building over a public sewer, requiring application, video survey of the old pipe(s) and lots of time for a draconian decision!
    • CommentAuthormarsaday
    • CommentTimeJun 21st 2017
    We both have extensions over the drains at the moment. Mine is a conservatory, his is similar. He has rerouted his drains i think in the past, but i am sure mine still goes under my conservatory. There is a very weird circular reroute of his overflow drain though and it circles under my conservatory and then heads back under his wall to the straight line of drainage. I also have a washing machine feeding into this weird arrangement. Will be glad to get new drains in.

    Under the water agreements, my side is privately owned, but his is owned by the water company. So if he gets a blockage on his side the water board sort it. I have to sort myself out, but luckily never had any issues.

    Thanks Tony i do understand the 45 degree workings as looked at that for the foundation. I think i will be ok seeing as the drain is 1.8m away from the wall.

    Does anyone know how deep my house foundation is likley to be though ? Build 1910. I will be digging down around the gullies to get lines over to the main sewer line so should find out, but always nice to have an idea of how deep these foundations were.
    • CommentAuthorCWatters
    • CommentTimeJun 21st 2017
    Does anyone know how deep my house foundation is likley to be though ? Build 1910.

    Impossible to say. Dig a trial hole next to the house.
    • CommentAuthormarsaday
    • CommentTimeJun 21st 2017
    Yes i will be doing, where all the blinking services come in as well !
    • CommentAuthortony
    • CommentTimeJun 21st 2017
    I reckon 12 to 18"
    • CommentAuthormarsaday
    • CommentTimeJun 25th 2017
    Yesterday i exposed the front down pipe drain which sits next to the drive in a flower bed. I am going to be tapping into this drain in the next few weeks. Right next to this was the main electric feed into the house. It comes in under the concrete drive and about 60cm in the flower bed and then enters the house.

    It is just under the 100mm of concrete drive + it enters the house one brick course below the DPC. There was a hole 3/4 brick size and it was partially filled with cement. No wonder the cupboard where the electric meter sits is always draughty and cold in the winter. I have filled this gap with expanding foam and will cut out and finish with cement.

    I have also seen a little more of the foundations, but not gone any further yet as had loads to do yesterday.

    There are 3 courses of brick below DPC and then there is one course of brick which looks like it is a type of floor construction as this course sticks out a little more than the other courses and are laid in a different direction to how bricks are laid. I will discover how deep this foundation is soon.

    Another question if i may. I am also replacing the lead water feed for MDPE. The line for gig runs 450mm next to the building and it will go all the way to the rear. So my trench for the water feed will need to be 750mm deep. Obviously i am a little worried about digging this line the full length of the house because it is close to the foundations and i imagine it may not fit under the 45 degree rule.

    So do you think i am ok to dig if i do it in stages? With a mini digger i can do it all on the same day. So if i dig a 3m section, lay the pipe and then fill with some pea gravel and then refill with the dug material the ground should be ok?
    Until you have dug out to find the depth of the foundations it is not possible to advise on the best method of putting in the new water pipe! It may pass the 45 degree rule.

    Can you move the lay of the new pipe further away from the wall? - every little helps. Also make sure that when you dig the trench it is as narrow as possible and the as far away from the house as possible i.e. plan to dig the trench so the lay of the pipe is to be on the side of the trench closest to the house.

    I would have thought that if the trench has to be in such a place that the 45 degree rule fails then 3M at a time is too much. Don't forget you will be digging out consolidated soil and back filling with loose soil so the support given by the replaced soil will be a lot less than what you remove.
    • CommentAuthormarsaday
    • CommentTimeJun 25th 2017 edited
    I can move the pipe more to the left in the drive, but i thought it was best to go in a straight line up from the stop cock in the pavement. I will be digging next week so will dig deeper to see what foundation I actually have.
    • CommentAuthormarsaday
    • CommentTimeJun 29th 2017
    I have dug down today and i have some photos of the depth.

    From the bottom of the foundation, which looks like it is a bit of rubble below the last brick, up to my finger which is the DPC, the distance is 600mm.

    I will post another photo showing a little closer and lower in the trench.
    • CommentAuthormarsaday
    • CommentTimeJun 29th 2017
    Another pic.
    • CommentAuthormarsaday
    • CommentTimeJun 29th 2017
    I have bought a protractor today and and from the bottom of the foundation line i think a trench starting at 500mm away from the way and being 300mm wide will pass. I have also based this on the foundation being only 450mm deep because i am not sure how you actually measure these brick type foundations. If you measure from just below the DPC then it is 600mm, So 450mm is certainly the area below ground level and it seems to pass.

    I also spoke to a drive installer today and he said these houses will easily take a water feed trench quite close. So feeling confident and i also have a bit of flexibility on position.
    • CommentAuthorcjard
    • CommentTimeJul 4th 2017
    My building inspector said he wanted my drains in at 1:80, rather than the 1:40 I thought I should have used. Most helpful for one particular run where I couldn't get much fall..

    If you want to check fall over a distance you only need a bit of clear plastic pipe filled with water- when the ends are held up the meniscus at each end will be level, so measuring down from it gives the relative heights of the two ends

    Tom, I'm not sure I'd be relieved to be relieved of shared drain ownership; I think it highly beneficial that it be the water authority's problem if a drain on my land suffers some malaise
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