Tony L

Thanks, @ProDave. Is it best to use bricks or cuts from 7N blocks with max. 10mm mortar above & below to create this "build up"? Then, presumably, we can continue the wall upwards with 7N dense blocks sitting on top of the section of the B&B that's supported underneath by the piers - so this wall will cut through the insulated floor. Should a special brick/block be used for the first course that sits on top of the B&B? This first course of internal wall is going to have the floor insulation either side. I'm thinking if we just go up with regular blocks, there will be a cold bridge.

Thanks for your input, everyone. Yes, I am already very concerned that he's taking advantage of my lack of knowledge & is cutting corners, & it's helpful to hear my view on this is supported by those of you on the forum who do have the knowledge. This builder has been employed to deal with demolition, groundworks including drains & connection to main sewer, building up the BB floor & also laying the courses of bricks that will take us up to where the render will start. I think we're 80% or more of the way there now, & I'm hoping we can keep an eye on him & complete this first phase of the project within the next two weeks. Although my partner has been expressing a "better the devil you know" view on who might be chosen to deal with the next phase of the build, I don't think we should consider continuing with this builder. I'm aiming to be well inside the airtightness value at which MVHR makes sense, & I think it would take too much of my time & energy to badger this guy into dealing with all the details to achieve that goal.

Thanks, @nod. I can see that's a better way of doing it, but as this wasn't specified in the brief he quoted on, I'm not going to be able to tell him to take the blocks out, lift the beam ends & use wider DPC, unless I want to pay for it, or do it myself - which I'd probably enjoy doing, if I didn't have a business to run. He told me, he'd told the BCO this is what he was going to do, & the BCO was OK with it.

How will the gap between the beams in the picture below be dealt with? Will the builder cut concrete blocks in half lengthways? I have a feeling I’m over thinking this, but I work on the principal that even if you’re 99% sure, if you’ve time to ask someone who knows, you should ask. & sorry for all the questions. I will, of course, be asking the builder, but based on his performance over the past month, I think it’s as well to try to learn as much as I can here, because I don’t trust him to always offer me the best possible solution, or even do what he told me he was going to do the day before.

I’d just like to check that it’s normal to fit blocks with bits missing from the edges into B&B floor. Will the builder just stick some mortar into these? If so, will it matter if the mortar slops down to form a bridge to the wet ground, about 250mm below the beams? Once the B&B floor is done, it will likely be many months before we start building the walls. Should I tell the builder to just leave the holes, in case his weak mix (relative to concrete blocks) deteriorates through the winter, & we can fill the holes when we’re ready to build up the floor? How will the small rectangular holes by the sleeper wall be filled?

I can’t see what’s going on on the other pier because all I see is B&B covering it. I’m surprised to see it being built like this. Perhaps the builder will remove the blocks & build up under them, so the blocks are supported, on top of the foundation. If that’s his plan, what do I do about mitigating cold bridge? Do I stick some Marmox blocks in somewhere? Where? I don’t know much about these. I need to learn. The sleeper wall within the green ellipse at the bottom of the picture is intended to support a wall that will come up about 1m above FFL & support one side of a landing just under half way up the stairs. So this wall will be supporting the staggered ends of short beams. Presumably, I can build my 1m high by 100mm wide wall, to support one side of the 180 degree turn landing, from concrete blocks, directly on top of the beams. Do I need to worry about cold bridge here? The beams are resting on aerated trench blocks, so not as bad for cold bridging as would be the case if they were resting on regular 100mm concrete blocks.

My B&B floor is more than half complete. Over the weekend I made a site inspection & I can see that the B&B floor has just been put over the top of these two foundation piers. In the picture below, there’s a gap of several cm between the beam, which is off the right edge of the sleeper wall underneath, & the sleeper wall below.

My foundation plan looks like this: The two piers that are right in the middle (I’ve drawn a purple ellipse over one of them) are there so the entrance hall (in the middle at the bottom of the picture) will be open plan onto the kitchen, which is in the middle at the top of the picture. I envisaged 100mm wide concrete block piers being built up off the top of the poured concrete foundation (where the piers are) all the way up to the RSJ that will support the side of the landing that overlooks the galleried entrance hall. The top of the stairs may also be supported on this RSJ.

Thanks, @nod, that's reassuring. @Russell griffiths. Thanks for the suggestion. I don't think it's a good idea to tell the builder to stop work for a couple of days & pay his team to do nothing, or if they have another job to go to, they may lose momentum on my job. I don't want him to start thinking I'm being unreasonable, even though he has disappointed me. Drainage is around the other side from where the pictures were taken. It's good to learn the bits that are missing are called "dolly blocks". I will ask him about these. @Oz07. Thanks. I guess wrapping the DPC back over the beams isn't an option for me because my air bricks are going to have to go in between the beams. I was expecting them to be lower, but I don't suppose it matters. I know some beams have exposed steel bars showing at the ends & I'd probably have sprayed bitumen on the ends if this had been the case for mine, but all I see is concrete.

& what’s been built doesn’t match any of the diagrams I see on the internet, which mostly have a gap beneath the insulation to help any water in the cavity drop down onto a slope that directs it to the outer leaf. The drawings the builder is working from show beams sitting on DPC on the inner leaf of a cavity wall. I can see this makes sense, because any water inside the cavity wall will drop down beyond the beams. With the arrangement that’s been built, any water in the cavity could pool right next to the beam & as soon as it’s 2mm deep it will be over the top of the DPM & onto the beam. He told me he was going to put a tray in, but it seems to me this tray will not be in the best possible position. & if there’s a tray sloping to the outside wall, doesn’t that mean there will be no insulation against the B&B floor? Air bricks: All the diagrams I see have the inner vent of the periscope lower than the beams – it doesn’t look like that’s what my builder is planning to do. The outer skin of the house will be rendered blocks. The builder knows we want standard size black bricks, beneath the render, going into the ground. Presumably, he’s intending to lay 2+ courses of black bricks on top of the edge of the trench blocks then build up the ground so we can’t see where the black bricks meet the blocks beneath ground level. I think there will be damp coming through from the ground & into the trench blocks the beams are sitting on. Does this matter? This (below) is much closer to what I was expecting:

What's built doesn't match the drawings the builder is working from (which I did understand). See below

Does this look OK? I don't understand how it's going to work.

I've left lots of detail out of my story, because there's a lot to it & a full explanation would be so lengthy nobody would want to read it. The 1m instructions were given when a BCO visited the site & inspected 2m holes I'd dug either side of the house location around 3 years ago, before we properly got going with the build. I didn't think we had time for an argument. The ground was unstable & the trenches could have collapsed. The shuttering had been engineered to last just a few days & the builder & I thought, if we don't do whatever needs to be done quickly, we could end up having to spend even more money to satisfy BCO. I was discussing this with another local builder a couple of days ago & he explained BC are a lot more strict on foundations than they used to be just a few years ago, especially when it comers to nearby trees.

I've duplicated some of this story in my separate trench blocks thread. Thanks for all the responses here. The work continues. I have plenty of sympathy for the builder. He is working hard in conditions that are more difficult than we anticipated. I agree, the ground is eating my budget, & the BCO has cost me a fortune by telling me to pay for something to be done then telling me, on his next visit, that what he asked me to do (& I've paid for) is not what needed to be done, & a new plan needs to be devised & paid for. My email to the builder was not dictatorial; I set out some materials calculations & asked him to comment on them or correct them. I was seeking clarity on how much of what I'd paid £17,000+ for had been done & how much had not been done - ie how much of the £17k+ should have been deducted from the subsequent invoice I received, which covered implementing the new plan that was required because the BCO didn't tell us he was concerned about the tree, on his first visit. The new plan replaced the £17k plan - it wasn't a case of, "Do everything I told you to do & do this extra work as well.". I'm more inclined to agree with Joe's view, "get it in writing", than pay for an off site meeting during which the builder must attempt to explain loads & loads of figures & a fair amount of maths. There's too much to take in if I'm listening to it all, rather than steadily working through an email I've printed out & can write notes on. We've had a good meeting since our email exchange.

Yes, but what kind of blocks? 7.3N concrete blocks (100mm wide) are normal, but I couldn't even find 7.3N trench blocks (350mm wide) when I Googled - they're all 3.6N. My partner called Travis Perkins & Jewson & they both told her, they can supply 7.3N trench blocks, but they're unusual, so they don't stock them; they have to make a special order. What happened was, after the BCO had told us to dig an extra metre down (& still pour only 600mm of concrete in the trenches), he made a second visit, to see the 2m trenches, & he pointed out a tree, which meant we had to change our plan again & pour a lot more concrete. I think the trench blocks were ordered when the builder thought he'd be building up from the bottom of a 1.4m trench (ie top of concrete 1.4 below GL), then when we were given the new spec' to deal with the tree, the trench blocks (over spec'ed TBs) had already been ordered, so he used them rather than send them back. I'm annoyed because I've got 3 courses of TBs on top of the concrete & that's got us up to the level to put the beams down. What's built doesn't look like the drawing the builder is supposed to be working from. I was expecting the beams to be sitting on the inner leaf of a cavity wall made from 100mm wide concrete blocks, but he's going to put down 100mm wide DPC on the inner edge of the TBs & sit the beams on this. He says he told the BCO what he intended to do & BCO was OK with it. I'll just remind everyone, I'm new to this & there are vast gaps in my knowledge, but my thinking is: each of these £10.71 blocks (certainly the top 2 courses) could have been two £1.50 100mm wide concrete blocks, with a cavity between them, & the additional labour to lay the second £1.50 concrete block would still leave a good saving over each £10.71 TB. Am I right?

Thanks for the tip. I will hopefully remember this when I eventually get onto my roof. I expect the GRP solution means there are no visible joints, which would be a big bonus.

He did. The original quote, based on 1m trenches included: Block solid concrete 7.3Kn 100mm cavity walls. Fill cavity with concrete to within 150mm of DPC level.

Thanks. Something to ask about before I accept a quote then. I have these switches outside my office, for my a/c, & some kids turned them off a few times. I didn't realise I may be able to lock them.

Thanks for the encouragement. I said I'd update, so: Confidence in the builder is waning. I'm too busy to trouble you with all the details right now, but the bill for the first lot of extra work was £17,700. The BCO made a second visit & decided a tree he hadn't seen on his first visit would require yet another plan to be devised. This second BCO visit resulted in another bill for extras from the builder. I said, "But now you're not building everything that was included in the first bill for extras. The invoice lines on the 2nd bill might be OK, but you should have gone on to deduct some of what was on the first bill". The builder has now agreed a small deduction should have been made, but I think it should be much bigger. His explanation of the various costs is not clear. I want it all explained in an email so I can pick through it carefully. He says he's not good at email & he's pressurising me to run through it all at a site meeting.

I have a bit of a dispute going with my builder who’s dug footings, poured concrete, laid 3 courses of trench blocks & should be going on to top this off with B&B floor then dig drains & make a connection to the sewer. We’re building a 1.5 storey house, block inner & block outer walls with render. After a visit from BCO & SE, we needed to abandon our plan for 1m trenches with 600mm poured concrete, & dig deeper trenches (1.95 across about 25% of the trenches & 1.65 deep on the rest) & pour more concrete, to take the level up so there was no more than 650mm of “trench block/underbuild”, to quote the SE, below B&B. The builder said he’d not allowed for any trench blocks o in his original quote, however, his invoice for extras resulting from the BCO visits includes £3215 for trench blocks. That’s just for the blocks – he’s also charged £600 for extra sand+cement & £2400 (95m2 @ £25, yes rounded up by £25) to lay the 300 trench blocks & 500 regular size concrete blocks. The builder says the trench blocks cost £10.71 each. I said they should cost him less than £7 each (before VAT). He said they’re expensive because he’s used 7N trench blocks. They’re 440 long x 350 wide & I think they’re 220 high, but I may have the height wrong – some of these are 215 high. My first question is: how can tell if what he’s used are 7N trench blocks? My understanding is, it’s unusual for this type of block to be used in this situation. Are 7N & the usual 3.6N trench blocks different densities? How much should one of these weigh? He didn’t allow for any trench blocks in his original quote – he was going to build a cavity wall straight off the concrete at the bottom of the 1m trenches. He hasn’t yet explained the benefit of the trench blocks over using regular blocks + cavity.

It's disappointing to hear the vendor is not offering sufficient help. I'm in Surrey & I'll be shopping for an ASHP at some point during my build. Would you share the name of your vendor, please so I can be sure to avoid them? A message, rather than forum post would be great, if you don't want to run the risk of defaming these people on a public forum. I hope you overcome your problems soon.

My partner spoke to Openreach a couple of months ago, because we'd stopped using the line that was on the house about 2 years ago & we wanted it reconnected. She didn't mention the new house - it didn't seem relevant; we just wanted a phone line that worked so we could ditch the 4G router we'd been using & have reliable internet again. I'm not convinced anybody will be laying fibre to the houses in our road any time soon - the houses are quite far apart. I wish I'd thought of this sooner. The run goes across the driveway & just a few weeks ago, we dug a new ditch & moved the services for the caravan into it, then made good so the muck away trucks, etc could drive over it. Never mind - it's only a small mistake.

Thanks, everybody. So the answer to my problem is: the detached garage. Why didn't I think of that? Virgin isn't an option down my road & I have Virgin at my workplace (my own small business) & at my mum's (which I look after), so I know I wouldn't choose them even if I could. So the next thing I need to decide is: do I let the builder put the copper telephone wire in the same 110mm conduit he's using to run SWA from the garage to the house? I'm planning to have my elec meter on the back of the garage, out of sight. The meter will be about 20m from the consumer unit, in my utility room. I'm concerned the elec will cause interference on the copper telephone line. I suppose a separate run, at least 1m away, would be best, but I don't really know what I'm doing, which is why I'm here.

The concrete was poured this week & my builder has just started laying trench blocks today. Before we knocked the old house down, I took the BT copper wire off the apex of the roof & fed it into the our static caravan, which is our temp accomodation. A friend who knows more about this than me came & installed the wall box in the van. I’m fairly sure he installed two boxes, so our telephone wire that’s outside goes into one box, under the van & this feeds into another box by the skirting board inside, & we plug our router into this box. I asked my builder to put some conduit across the garden & through the wall below ground level, thinking I’d have both telecom boxes, as described above, in the corner of a room at the front of the house where I’m intending to build a cupboard – so they’d be hidden. He tells me, I must have the BT box on the outside of the house (above GL of course), so BT can maintain it. This may be the preference of Openreach or whomever, although they may be happy to have their box out of the weather; my preference is to not have their ugly box on show. Should I go with my plan, or the builder’s plan?

Good point, ProDave, but is this something that ever needs to be done? I suppose you could have the underground pipes passing through one of those cheap plastic inspection chambers if you're concerned you may need to bleed, in future. To answer Joe's question (although it was directed at Nic - sorry, Nic): I'd planned to put my ASHP against the wall on the south side of my house, which would mean it would be a prominent feature in my small patio + back garden area, but these things are so ugly (& there's the noise & cold draught to consider as well), I'm thinking it may be well worth be worth the additional installation, running & maintenance costs to put it out of the way, against the boundary hedge to the east. That would put it about 4m away from the house. This would mean the pipes would have to go underground, & if they're underground they may as well come up into the house through the block & beam floor. Please have a go at dissuading me. While I'm on the subject, I'll just ask, do I have to have one of these electric isolator switches, as shown in the picture, below? Does it have to be outside, near the unit or can it be in the house? The electrician who made this video explains it must be at least 200mm away, but he didn't mention a max. distance.