Shallow drain under extension - and routing query

[Baz100]

All

We are buying a house and plan to add a rear extension. Went to view today to measure up and check for drains. The Foul and surface inspection chambers are right where the extension is going to go.

qu.1. I don't want to have to have access to inspection chambers in the extension (tiled kitchen floor) so I plan to relocate, what is the best way. I wondered if I could 45 degree and extend all pipes out the footing under a lintel and make a new chamber in the garden (see image). Is this OK, or is there a better way?

qu2. The surface water looks about 550mm below DPC level, but the foul looks very shallow, approx. 400mm below DPC. I was wondering how this would work with my concrete floor? As far as I can understand the regs, with 60mm insulation, the floor will be 400mm min thickness. If there a minimum distance below hardcore that the pipes can sit? or can they be touching, or within the hardcore layer (obviously protected with finer material).

Many thanks

Baz

 

[r1flyguy]

Hi Baz

Q1. I've been lead to believe this is a no-no now, your not allowed to have chambers in the footprint of your structure anymore thus it will need to be moved. Albeit someone on here may have a better understanding than me.

If your moving the pipe work you 'may need to renew the length of foul pipe that runs across your property so that you can tap back into it at a more convenient point. I renewed the complete length of mine for obvious reasons.

You will also need to inform/apply to you local water company for 'permission' to 'alter' any pipe work 'they' own & once done have a survey of it to make sure it's fit for purpose and 'complies with their regulations

2. I'm not 100% of the depths of ours but are you talking about the pipes 'from' the property and not the ones they actually run in to?
Any pipe work will need to be covered completely with pea gravel then hardcore.

If you look at the very start of my thread here //www.diynot.com/diy/threads/hi-all-newbie-here-in-midst-of-extension.432509/
You will see what we did

Any questions please feel free to message me

 

[noseall]

I can't see a lot wrong with your proposals other than you will need to keep the drain runs straight where you are able. If you do need a change of direction do it with a slow bend.

 

[^woody^]

You can have manholes within buildings.

If you can provide rodding access elsewhere, you can seal the manhole up

 

[Baz100]

Thanks all for your replies.

r1flyguy - great pictures of your project! Luckily The pipes are all private and cater only for the detached house (as far as I can tell) and only enter the adopted public sewer chamber outside the boundary, so we are free to modify as we wish and just need building regs signoff rather than water board approval. I would rather move the inspection chambers outside the extension anyway, we will have a tiled floor in the extension so cannot cater for a chamber.

The depth I was referring to is the current depth of the services at the current inspection chamber just outside the current house (top image) , but in the centre of the proposed extension.

noseall - I am still working my way through all the reg documents, but ive heard a few places that you are allowed up to 45 degrees bends that are not serviceable, is that right? Are slow bends available in anything other than 90 degrees? I plan to cut the current pipes at a suitable location and 45 degree bend them using new pipes and fittings out of the extension through a lintel in the foundation. The pipes are 30 years old, so I assume they are compatible with current plastic pipes.

woody - the 2 soil pipes in the images are from WC stacks, so I don't think we will struggle to be able to rod them at source? I cant remember seeing any exposed stack with rodding points.

 

[r1flyguy]

Great news on your waste being private, saves so much hassle that's for sure.

You can by slow bends no problem, also most connectors from clay to plastic too if you have clay.

You can also by a curved 110mm pipe and just cut the angles you require at the join and use a rubber flexi join if needs be unless your smack on with your angles.

I have a huge pile of brand new connectors & pipe (over purchased ha ha) if your thinking of doing the work yourself I'd be happy to sell to you very cheap


Shop around for your underground pipe work as the price varies astronomically and is laughable at times

 

[Baz100]

Thanks for that, ill let you know. Still a way off as we haven't quite purchased yet (solicitors taking an age!) but I'm just getting the building regs plans drawn up and I will submit them as soon as we have exchanged contracts. Hopefully then we should have plans approval a few weeks after we 'move in' to start the work. Dead keen to get the messy work done before we actually move all our things in to the rest of the house. Were doing a full width back extension, so looks like its fully covered under permitted development.

I have got through your images and have a few questions.
1)How close was the neighbours tree that caused you to have deeper footings? (we have a couple of conifer trees in the garden that I am now worried about)
2)We will have a rafter level ceiling too, but I am struggling to choose a roof insulation method. I kinda decided on insulation between rafters (lower) and then insulated plasterboard with VCL, with the void at the upper between rafters and using non breathable sheet. Looking at yours it now seems to make more sense moving the insulation to the upper void because of all the cable routing. What made you go with that method? I think I decided on mine because we were tight for overall thickness and it didn't allow for counterbattens with the 17.5 degree pitch vs existing upstairs windows. Going to revisit my thinking now.
3) Where did you get your materials from? I have sent out a RFQ to Jewsons etc for the entire build materials, and none of them can come close to Wickes (And I get a further 10% off at Wickes). Things like insulation it seems a bit cheaper to buy online, but everyday things like blocks, sand, cement, timber, T&G boards, plasterboard Wickes seem to have it cheaper. Bricks will need to match, and we have a local yard that can match, and they seem pretty good value.

 

[r1flyguy]

I have got through your images and have a few questions.
1)How close was the neighbours tree that caused you to have deeper footings? (we have a couple of conifer trees in the garden that I am now worried about)

Within a couple of feet, literally & very close to the obs chamber in his garden which my neighbours & my foul runs into and which I forsee it breaking into at some point.

 

[r1flyguy]

2)We will have a rafter level ceiling too, but I am struggling to choose a roof insulation method. I kinda decided on insulation between rafters (lower) and then insulated plasterboard with VCL, with the void at the upper between rafters and using non breathable sheet. Looking at yours it now seems to make more sense moving the insulation to the upper void because of all the cable routing. What made you go with that method? I think I decided on mine because we were tight for overall thickness and it didn't allow for counterbattens with the 17.5 degree pitch vs existing upstairs windows. Going to revisit my thinking now.

There is an option to increase the roof pitch and have it either side of the upper floor wind with the roof pitch below the window tied in if you know what I mean. We didn't do that obviously but a local property has done it this way and doesn't look too bad in all honesty.

Our architect (or uncle ha ha) provided us with the idea for the insulation and the wiring for the down lighters worked out well with this.

There's plenty of air circulation up there to dissipate any heat off the lights (if any and the cut outs in the insulation were kept to a minimum using slimline down lighters as recommended on this site.

The rafters are 150mm as opposed to 100mm too

 

[r1flyguy]

3) Where did you get your materials from? I have sent out a RFQ to Jewsons etc for the entire build materials, and none of them can come close to Wickes (And I get a further 10% off at Wickes). Things like insulation it seems a bit cheaper to buy online, but everyday things like blocks, sand, cement, timber, T&G boards, plasterboard Wickes seem to have it cheaper. Bricks will need to match, and we have a local yard that can match, and they seem pretty good value.

I've purchased supplies from most of the local building suppliers based on quantity, bulk savings, delivery costs.

The trouble with some are the quality of the product, wickes are good but you really need to specify the sand for bricklaying as you might get red or yellow and have different colour mortar.

Mot type 1 I purchased from local aggragate company at a third the cost of the likes of buildbase/wickes

Pea gravel for pipe work was from wickes, buildland, Jewsons, all depending on what I was ordering at the time and cost savings.

Insulation I purchased from a 'contact' and saved a considerable amount

Bricks & blocks were from EH Smiths and cheaper than Travis Perkins for brick matching

All the steel work was from a company who fabricated my requirements and about 20 miles from where I live as the company '1' mile from me was 20% more expensive including delivery!!!!!

 

[Baz100]

Sounds good, was it just the brickwork/trusses and calculations you contracted out? I was expecting to see a lot of people saying 'get the experts in', so I'm glad other people have done most of it themselves.

I have an opening to make in the existing house, so need a RSJ. I was tempted to do the calculations myself. I have all the British standards for the calcs and spent some time going through them and are confident I can follow. I'm no civil/structural engineer, but I am a mechanical one and sat most of the same mechanics lessons a Civil engineer would sit. The British standards calcs are just basic beam calcs, but they go about them in a different way to what I was taught. Anyway, I used both methods and gave the same results so I'm happy to follow the British Std method to satisfy what a BI would be used to. I guess its down to him if he will accept calculations from someone not strictly a Structural engineer, but if I have shown I have followed all relevant standards I hope it will be OK. (to be honest, it looks like some councils give very general guides for beam selection vs span so if it exceeds their spec, some councils BIs don't even look for calcs by the looks of it) .

 

[r1flyguy]

Our uncle had contacts for the structural calcs and at £50 per spec sheet I didn't argue. At least they were drawn up and provided for showing the Building regs that we have complied if not exceeded the requirements.

The brickwork was started by one recommendation but with my father being a builder of many years and not happy with the progress they didn't take too kindly to being told how to do their job and left which was fine by me as the lads who came in to finish the job were '**** hot' in my opinion and well worth the money.

I spent a lot of time compiling building products required at each stage and pricing around.
A lot of the work we have done ourselves but I will say I have qualified, electricians & a plumber to do that side of the work as I won't touch what I have no idea about & im happy to tell them exactly what I want and where I want it.

As long as you have the time to source products you will be gobsmacked at the price differences for the same item!

Also plan well ahead

I purchased twin sockets with USB ports about 6 months ago when screw fix were doing a deal on them
They were only fitted a couple of days ago !!

Truthfully, I'd love to build a detached house from scratch, maybe one day.

 

[r1flyguy]

The trusses & post joists were calculated and then I sourced various companies before finding a local company who were able to make and deliver them in good time.

It's amazing what companies you can find local to you when you make a determined effort to source what you need

 

[noseall]

And I bet you did it all during the recession too. Great being a diyer and having lots of spare time and zero loyalty to building trade suppliers.

 

[r1flyguy]

And I bet you did it all during the recession too. Great being a diyer and having lots of spare time and zero loyalty to building trade suppliers.

Excuse me!!! You have a problem with how I spend my money on my home!!!

Which recession are you talking about and what makes you think I have a lot of spare time?

I was in the building trade but have a different profession now, my father has built factories, houses, etc, and truthfully I don't give a **** about loyalty to trade suppliers, I'm don't hold a trade account with anyone so I've paid over the odds to everyone who does have a trade account, thus I'll search for the best deal just as you would!
As for trades persons, I'm loyal to the electrician & plumber I've used for years and my fathers building colleagues who ive used also.

So please go preach to someone else until you know the facts about my background