Ian

I am a Chartered Architect and also carry out work regularly as a CDM Principal Designer. Within my company I also employ CDM specialists who do nothing else other than working as CDM Principal Designers. In my opinion the guidance in this thread by @JSHarris is correct.

Not sure why you need a drop shaft for the surface water sewer. You can go for a steeper gradient for the SW sewer run as you are not bound by the same gradient restrictions as you need for the FW. You'll still need a manhole where you have a change in gradient but it doesn't need to be a back-drop.

apologies - I see what you mean. Edit: Have you compared the cost of your 2 back-drop manholes compared to just digging your drain runs a bit deeper?

@Barney12 Also, I'm not sure what these 2 manholes are for. If you're not connecting any side branches into them you'd be better off without them with the added bonus of saving a bit of money.

@Barney12 Just one small point regarding your foul run: If you are intending using pre-formed plastic manholes then you would be better always having the main run of pipe connecting on the axis of the manhole and not on a side branch pipe connection as this sketch. The reason is that the pre-formed benching of the main axis run of the plastic manholes are set slightly lower than the branch incomers. If you don't connect to the main axis, waste will sit trapped in the dead end of the main branch run.

The Building Regs Approved Document says no surface water soakaways within 5m of the building. The concern is that the soakaway can affect the house foundations. It's something I've seen myself several times when rwp connections have failed (split) underground next to a house. The water can wash away the fines in hardcore leading to subsidence. Edit: The land drain that @JSHarris will have installed isn't classed a soakaway as I'm guessing that the pipes he's talking about are designed to remove water from the ground rather than to act as a soakaway (the perforations in his pipe will have been at the top of the pipe and not the bottom)

Another one for the database: £4,800 supplied and fitted Rehau Upvc system with 3G 44mm units using their standard (dark grey coloured) 5 chamber 70mm frame. Combined 0.8 U value. Price included for 6 'normal' windows, 2 french doors (fully glazed) and 1No front door. Total area 18.5sq.m. £259/sq.m.

Small correction for those living in England: The max size was amended in 2006 in England (not sure about Scotland & Wales) the max size is 20m x 6.8m external and 3.05m internal ceiling height. There's no restriction on external ridge height.

It's worth asking your Building Inspector first as they have the authority to allow variations to the requirements laid out in the Approved Documents

@Construction Channel CDM = Construction Design & Management Regulations. Its health & safety legislation specifically for construction that was first introduced in the U.K. way back In 1994 and then amended in 2015. The purpose of it was to make the construction and maintenance of buildings (and other related structures) safer. It's had a major effect on the way that safety is approached and nobody I know in construction would want to go back to the dark ages of what it was like on building sites pre 1994. My first job after qualifying as an architect in 1987 was to design a large industrial building. The steel workers erecting the frame did so 10m up without any safety netting or safety harnesses and when the roofers were installing the large metal roof panels it was a windy day and one blew away, travelled over all 6 lanes of the M62 and landed on the far side. Looking back it was a miracle nobody was killed on that site but pre-1994 and CDM that's what it was like on building sites. Likewise architects like myself and other designers (structural and M&E) would commonly design buildings without seriously considering how they could be safely and easily maintained. These days as an architect on every project that I am involved with I've got to formally consider safety (i.e. written risk assessments and method statements) and show how my design approach has eliminated risk for the construction and maintenance of the building.

@Ferdinand From my experience Marmoleum (modern rebranded version of Lino) is more environmentally friendly than vinyl based flooring but it is not as resistant to point loads as vinyl - e.g. Stiletto heels. Marmoleum doesn't have the long term shrinkage issues that vinyl flooring can have if it is cleaned with the wrong products such as bleach based cleaners. Although not really the best choice for a bathroom there are also some nice click fit vinyl planks on the market that are a lot cheaper than Amtico. Luvanto is a good alternative to Amtico and a fraction of the price. They are much harder wearing than the laminated timber click fit alternatives.

@oranjeboom Is it possible to have 2 u/f heating loops? - one loop for each part of the slab. That way you could design in enough of a gap to have a (safe) saw cut along the dividing line between the 2 areas. Edit: if you are planning on installing the bamboo flooring as a 'floating' floor on an underlay there should be enough tolerance in the build up to cover any minor cracking in the slabs at the junction between the 2 areas. Any type of hard flooring that is bonded to the slab is the type that really needs a movement joint.

@Dee Sorry Dee, I didn't follow your earlier thread but the answer to your question is that clay tiles invariably weather better than concrete ones. By "weather" I assume you mean the colour of the tile changing over time. How long it would take to notice a difference would depend on the quality of the concrete tiles - some concrete tiles are through coloured and some only have the top surface colour coated. Edit: If your concrete tiles are old then they have probably done the majority of any colour change that they are going to do so you stand a better chance of the newly introduced clay tile still matching the colour of the concrete ones in 10 years time.

@oranjeboom Re the potential for cracking along the line of the joint I was thinking more that you have 2 different floor slabs next to each other - one has underfloor heating and one doesn't(?) + the extension is founded on piles and the original building is on ground bearing strip footings(?). If laying floor finishes that are in any way vulnerable to cracking it would be useful to have a linear movement joint in the floor finish along the line dividing the 2 slabs.

@oranjeboom won't you need a good solid support for whatever floor finish you put down over that area? Edit: unless you are going to be putting carpet down you'll likely need to install a movement joint in the floor finish along the line between the 2 slabs. Ceramic floor tiles or vinyl flooring will need a movement joint.

@Barney12 Maybe you're thinking of positioning electric cabling on a wall (no diagonals allowed there!)

@Barney12 I'd be tempted to go with the 2nd option and run the small diameter wastes direct to the WC soil stack. Could you not take a direct route to the WC stack instead of introducing 90 deg junctions?

@Dudda I agree with you completely! If you pick the right system and use that stick on profile that you mentioned its extremely difficult to tell the difference between the single ply membrane and metal. I've specified roofing like that several times near the coast where metal corrosion would be problem and also inner city areas where metal theft is an issue. Also, metal roofs can sometimes lead to problems with noise transfer into the building from rain drumming on the roof.

@Declan52@JSHarris Iceland is such an amazing place. I went there a few years ago to do some photography and took some shots of the blue lagoon and other geo-thermal power plants:

@divorcingjack The HSE guidance on this is very clear. Link here: http://www.hse.gov.uk/construction/cdm/2015/domestic-clients.htm I've cut & pasted the official guidance below but basically what it says is that if you are a domestic client (see definition below) then your client duties get automatically passed onto the contractor. Domestic clients: roles and responsibilities Construction (Design and Management) Regulations 2015 (CDM 2015) CDM 2015 makes a distinction between domestic clients and commercial clients, who commission construction work as part of their business. A domestic client is any individual who has construction work carried out on their home, or the home of a family member, that is not done as part of any business. While CDM 2015 places client duties on commercial clients in full, such duties for domestic clients normally pass to: the contractor, if it is a single contractor project, who must take on the legal duties of the client in addition to their own as contractor. In practice, this should involve little more than what they normally do in managing health and safety risks the principal contractor, for projects with more than one contractor, who must take on the legal duties of the client in addition to their own as principal contractor. If the domestic client has not appointed a principal contractor, the client duties must be carried out by the contractor in control of the construction work If a domestic client has appointed an architect (or other designer) on a project involving more than one contractor, they can ask them to manage the project and take on the client duties instead of the principal contractor. The designer then takes on the responsibilities of principal designer and must have a written agreement with the domestic client, confirming they have agreed (as principal designer) to take on the client duties as well as their own responsibilities. Any designer in charge of coordinating and managing a project is assumed to be the principal designer. However, if they do not have a written agreement with the domestic client to confirm they are taking on the client duties, those duties automatically pass to the principal contractor.

@Ferdinand Agreed!...that was one of my all time favourites from Grand Designs. It had a lovely feel to it! She's a very talented lady.

@Dudda The title 'Architect' is protected by law in the UK too. There's a big difference in length of time required to train to be an architect compared to an architectural technologist or architectural designer. Typically its 7 years instead of 3 years training.

@Vijay Pages 20 & 21 of this NHBC Foundation design document is a decent guide to the detail you need: http://www.home-extension.co.uk/nhbc foundation guide.pdf Yes, the joints and the lintel are to allow for movement. They are there to minimise risk of the pipe breaking. Have you built the foundations already? If you haven't already built them then the usual approach is that you locally set the depth of the foundation to suit the drain depth. Normally foundation depth isn't a problem unless you have a long internal run of pipe before you get to the external wall (eg a WC positioned in the middle of the house plan). The alternative approach if your WC is on an external wall is to take the drain through the wall above ground to an external soil stack but that can bring extra issues re air tightness unless you plan carefully for it.

It depends where you are in the UK. In England & Wales BCOs usually like to see an inspection chamber or at least rodding access at these type of junctions. In Scotland the building regs take a slightly different view - for example BCOs there don't like any manholes inside the footprint of the building (outside the building is ok).

@Vijay The normal way to do it is to put a lintel in the wall of the footing and use a short section of pipe with a joint each side for the part where the pipe goes through the wall. Going through the wall footing (using a lintel) is normal but not through the actual concrete of the foundation itself or below it.