MortarThePoint

I think I have probably been too trusting. They used an EDM to mark out and I checked the mark out as best I could, but more experience would probably have made me do some profiles or outside foundation marks for checking as well as a bit of double checking with tape measure or EDM.

I'm hearing good vibes which is encouraging ?

They clearly didn't dig centred on the line. They used a 600mm bucket and I guess they may have widened only on one side. That's the only way I can guess they have done it. No profiles unfortunately.

Thanks, this is good to hear. I worry about it being off centre putting a moment on that part of the foundation that effectively increases the pressure below one side of the foundation section. I expect I'll need to check with the Structural Engineer.

Separate to a discussion on tolerances, I wanted to start a new thread focused on a possible issue with how my foundations have been positioned. I used a tape measure to measure lines the groundworks team had sprayed out lines that represented middle of the trenches and they agreed with the drawings to within what I thought was an acceptable amount typically less 30mm difference. Since the trenches have been dug and poured it is hard to measure dimensions, but I am sure that one of the easiest to measure dimensions is out by 200mm. The wife's face was a picture when I explained to her that the kitchen had just shrunk by 200mm though it's actually the whole of one side of the house. Worse, we are preordering precast flooring that needs to fit. This is a bit of a worry. I measured centre of trench to centre of trench using a tape measure in the three positions (along A, B and C) and all three were under by ~200mm. I sent the drone up and I think this image captures the problem. The orange lines superimposed are the walls construction drawing. I laid some timber in the trenches to have reference dimensions. Now I'm hoping the bottom left hand corner is due to lens distortion so let's not go there yet. I don't have an EDM or anything to do better 2D measurements, but those three 1D measurements have me worried enough. With the rear wall (top of frame) centred on its trench the wall going left to right along the centre line is off centre of its trench. It just seems like that whole trench is out of place. That trench is specified to be 850mm wide and have a very structural wall on it which is 215mm wide. If the blockwork was laid out ignoring the trench misplacement it would look like the image below, 200mm off centre (blockwork in blue on top of foundation concrete in grey). That level of off centre looks alarming to me. What do people think? Am I rightly worried or does everyone have walls well of foundation centre? Some comfort and cold beer required.

I measured how they had sprayed the foundations out, but can only imagine what they would have made of it if I had started measuring the trenches as dug before the pour. Not particularly practical with a tape measure as well due to tench side collapse potential. Well since it has been poured and gone off I have been out with a tape measure ? I think I'd better start a new thread for thoughts on that.

Just to be clear the "That's nuts!" comment was about the swimming pool ? My groundworks guys dug to sprayed lines and the only measuring going on was for level/depth. BCO didn't go down and measure any stiffness, but gave things a good eyeball.

Is it normal to survey between dig and pour of the foundations to check that they are correctly dug? That's nuts!

I've seen there is quite a big gap between theory and practice so it is very useful to have real world numbers. My "brick or block level" was thinking above DPC, but I would hope the plumbness applies below DPC too. I don't find it stressful dealing with large tolerances as long as I have a feel for what they should be. Measuring something say 30mm out and having no idea what is reasonable is where the stress comes in. I'm cool if a room ends up 30mm smaller, but not if a doorway does. Some things are largely aesthetic (brick level and perp alignment every other course), some things functional (having a crapper in the corner of the living room rather as intended next door in the toilet) and some structural (plumbness).

I'd prefer to readjust. It's always been a pet peeve of mine when people have not thought about tolerances and default set very tight. I saved a previous company I worked for >£30k on a 10,000 fps high speed video camera that was proposed to confirm that an event happened within less than 100ms. I was able to show it using my phone at 120fps and we went with a rig using a 1200 fps point and shoot camera with an LED attached to a calibrated signal generator setting a reference timing. The event was always faster than 50ms. Would have been cool to play with the 10,000 fps camera though.

The groundworks crew used something like that to spray out the foundations. I measured it with a tape measure over the following weekend and was really impressed. It was about +/- 30mm typically and I was using a tape measure over rough ground so some of that will be on my measurement. The sprayed line has a width anyway. I did notice that they had misread a dimension though and lined up two walls that weren't supposed to be.

I've found some NHBC guidance for some of these: http://www.nhbc.co.uk/NHBCpublications/LiteratureLibrary/Technical/filedownload,15912,en.pdf but it's to do with finishes really. Brick or block level: +/-8mm over 5m, +/-12mm over further Brick or block plumbness: 8mm over 5m, 12m for higher but 8mm per storey

I want to be sure I have realistic expectations as it saves grief and means that I can tweak to accommodate the appropriate tolerance in advance.

That's some serious bedtime reading!

Hard work in a different way, but what about using a Tamper:

I've worked in the world of precision engineering for many years and as a self builder know that I need to adjust my expectations from dealing in fractions of a mm when it comes to tolerances. I'd be interested in people's views as to tolerances on the following (my current naive expectation in brackets): Foundation lateral placement (ignoring due to local side collapse) (+/-50mm over 5m) Foundation level (+/-5mm over 10m) Brick or block lateral placement (+/-10mm over 5m) Brick or block level (+/-5mm over 10m) Brick or block plumbness (+/-5mm over a floor) Lateral pipe of socket placement (+/-25mm) Window of door opening dimensions (+/-5mm for normal sizes) Feel free to add to the list as there are doubtless many areas I haven't thought about. My expectations have come from what I feel is practical, but I can't defend them much beyond that.

Well I didn't expect so much ramp discussion although it is interesting. Sounds like there isn't any minimum cover required by building regs. I have a run that needs to go a total of about 35m so it may start pretty shallow and end 2 or 3 feet down. A gradient of 1 in 80 is OK for a family of four sharing a house isn't it? That would be a drop of about 450mm.

Sorry if the question has been asked before (I did do a quick search) but I'm really tired after a couple of hard days and Part H is confusing me. Can someone be kind enough to advise me as to what the minimum depth is for foul water pipes running along side the house and then across the garden to a sewage treatment plant is. I see information for fields and roads but not garden etc... I guess it may be different near the house from in open garden. If the regs don't set a minimum depth, then experience appreciated. There are some things you don't want to step in when walking in the garden and, without a dog, this could be the greatest risk.

Interesting thought. I just took a look here and the lambda value looks the same as the more performant mineral wools like Dritherm Ultimate at 0.032. I guess it could be an option if supply is a major issue as can be put in after wall construction. A nice thing about these Knauf insulations is that it uses ECOSE which doesn't use a Formaldehyde binder agent in manufacture.

I follow you, like this: With Flemish you put a stretcher next to the queen closer. Face 1 Corner Face 2 [Stretcher-][Head][Stretcher-][Q][Head] | [Stretcher-][Head][Stretcher-][Head] [Head][Stretcher-][Head][Stretcher-] | [Head][Q][Stretcher-][Head][Stretcher-] [Stretcher-][Head][Stretcher-][Q][Head] | [Stretcher-][Head][Stretcher-][Head] Where's my daughter's Lego when I need it?

Using Knauf Dritherm Ultimate 32 Slab insulation and considered various cavity widths: 100mm : U-value 0.27, DER 9.80 kg/m2 125mm : U-value 0.22, DER 9.76 kg/m2 150mm : U-value 0.19, DER 9.41 kg/m2 Overall the benefits of going thicker did not stack up for us, but it's a personal thing really as everyone has their own set of priorities on a build. We live at about 17-18 C during the winter and there are two stoves in the house that we can use. If it was to be oil heated, I'd fit a larger tank given prices, but it's going to be ASHP.

I don't understand this, are you able to share a picture?

Is that a typo (weeps or perps) as I'm not familiar with peeps? Completely agree! Not something to be rushed as it is a demanding bond, important not to undermine the visual appeal by not making good layout choices.

I'll be fine with the rough internal look of the outer leaf, it's not the finished face and I can't imagine it any other way. This straw pole seems to support opening the cavity slightly, I'm not keen to go as far as 125mm, but adding a few mm does feel sensible. Once I started noticing brick bonds I started really appreciating them. I wondered about Monk bond (stretcher-stretcher-header). It's going to be Flemish all round as it is in keeping with the broader style of the house.

My day job is as an engineer and I'm used to dealing in um so it's sometimes hard to adjust to the tolerances. I was hoping to do lots of the brick laying myself, but Covid-19 may make that non-viable unfortunately.