jack

FYI, this was a spammer (posted a spam link later in this thread), so his post has been hidden.

Awesome, you were playing the role of "Airtightness Champion": https://carbonlite.net/wp-content/uploads/2017/04/Aldas-12-Steps-to-Airtightness-revised-June-2019.pdf

That could well be what happened. I know, I did my garage floor with it. That isn't what I meant by "expensive". My main point on epoxy is that I don't like how it looks. As such, all I would achieve by putting it down is covering some stains. Even the modest amount it would cost to lay epoxy just wouldn't be good value (to me) in the circumstances. The door opening height wouldn't be affected. The problem would be that the unit is in one piece (including threshold) and difficult to move.

The doors that would need raising include: a 5.5 m long, ~900kg (according to the installer), flush threshold, triple-glazed slider, which is built in behind a wooden facade. two large, flush threshold, triple-glazed window doors. a 2+ m high, one-piece front door assembly with door and side window. two large, triple glazed windows with lower frames flush with the floor. The screed is on a slip membrane, so easy enough to separate from the underlying slab. While cutting it out would be messy and unpleasant, it seems to me it would be a much more straightforward and lower risk job. Epoxy coating would be a lot of expense to avoid looking at a few stains. I also don't much like solid colours on floors, as I think they show every bit of dirt and wear. That's why we went for concrete in the first place! Personally, I doubt I'd ever be able to justify the cost of replacing or covering the entire downstairs floor. I might, however, get just the kitchen done at some stage, since that's where 95% of the problems are. Can't see it happening for at least 5 years based on current household finances!

100% should be done before walls if you want an even result. Also, my recollection is that (at least with actual concrete) the grinding needs to be done within a certain period of pouring - from memory it was within a few days of pouring. After that, it hardens so much that it takes a lot more work and diamond stones to grind and polish. One other thing I forgot to mention: we were advised to keep it covered for as long as possible. We bought a load of correx sheets, laid them down, and taped all seams. Weirdly, ten years later you can still see lines showing where the joins were. I have no idea whether the joins allowed the underlying concrete to cure and/or dry out faster, but it's something to think about. To be fair, I'm the only one who notices them.

It's all relevant to the topic, so no issues from my perspective. Partly aesthetics, partly function (easy to clean, good for UFH). It was not a particularly cheap option. I think it was comparable to getting decent wood flooring installed, but it's been over 10 years so I don't remember. No, it's ordinary poured concrete. It had a tint added, so it's slightly darker than regular concrete. No fibres (wouldn't they show on the surface?). It had the aggregate mixed in. I don't remember them doing a dry shake, but it was a long time ago. Certainly no stones were visible after power floating. It took quite a bit of coarse grinding to start exposing the aggregate, and even after that, there are areas with little to no visible aggregate. To be fair, that outcome was partly driven by my wife, who didn't want a lot of it visible. One of the things that might have contributed to the couple of cracks we have is that our nominally 65 mm thickness is 10 mm less than the recommended minimum. They did warn us in writing of an increased risk of cracking, so I can't really fault the supplier. No-one's suggested torching, but the big stain is almost certainly too deep to be torched or polished out. I've considered repeatedly applying and mopping up a solvent to see whether that would help, but it's so far down the (long!) list of life priorities that I'll probably never get to it. *Thumbs up*

We still have visible bits of airtightness tape at the junction between plasterboard and frame in some of our reveals. Ours is a combination of bad window installation, sub-optimal taping, and careless plasterers who did everything the easy way. Personally, I'd absolutely do it myself if I were doing it again. I doubt it's difficult, but doing it properly takes good preparation, time, and attention to detail. There are good vids on YouTube showing what's required.

Mains voltage is RMS. Multimeters nominally display RMS, but I think cheaper ones do something like measuring the average peak and estimating RMS by dividing by the relevant factor (sqrt 2, roughly 1.4). This assumes a perfect sine wave. The further from a perfect sine wave the input signal is, the more incorrect the value will be. Better ones will display "true" RMS, which involves performing the actual RMS calculations based on sampled voltage values. There's a lot more to calculate, so you need more memory and processing power, hence true RMS meters are more expensive.

We have an MBC slab topped by a ~65 mm polished concrete screed that was installed by a specialist polished concrete company. A few thoughts in no particular order: 1. You can't predict the outcome of a pour The quality of surface finish of a structural slab can't reliably be predicted in advance, and it isn't necessarily to do with the installer. In our case, the slab was poured in January. I believe (without any real evidence) that the concrete we were supplied with wasn't ideal in terms of slump. I think, in particular, that it had too much water in it. In any event, we started pouring first thing in the morning, but even by 11 o'clock that night it hadn't gone off enough to power float. It got very cold that night and we ended up with really bad spalling on large areas of the slab. To their credit, MBC offered to fix at their cost by raising the frame and covering the slab with a self-levelling screed. We went with polished concrete instead so that wasn't necessary. The main point I'm making here is that if something goes wrong with the pour or finishing and you haven't allowed for the additional buildup of a screed to fix, you'll need to think about microscreed or other thin finish to rectify. 2. Polished concrete is usually not just "concrete" As others have said, ideally you should add the right additives to the mix and use a surface hardener (I think our guys sprayed something on right before the power floated, or maybe before they started polishing). I don't know how this all works when you're talking about doing everything based on the structural slab, but if you're getting a specialist in to do the polishing, you should probably be getting their advice in advance, and possibly even onsite input during and immediately after the pour. 3. Polishing is best done before the frame goes up We made the mistake of leaving the decision on flooring until the frame was already up. Large polishing machines can't get right up to edges, and corners are a real challenge. These areas are polished with smaller hand machines which definitely don't do as good or consistent a job as the large machines. We have lots of waviness and visible artefacts along edges and in corners. We've convinced ourselves they add character. We also have a couple of large cracks. We did have crack-relief cuts made in the appropriate places, but because the frame was in the way, the cuts couldn't be made all the way to the edge. This wouldn't have happened if it had all be done before the frame went up. 4. Polishing isn't perfect Along with the edge and corner inconsistencies, we have several spots in our floor where you can see blade marks from power float being stopped. They look like big '+' signs. The underlying aggregate is inconsistently exposed. This is something you might be able to improve by being present during the polishing (and particularly the early part where the coarser grinding is done). Yes, and yes! Our floors are completely covered in fine surface microcracks. You can't see them in most places unless you look closely, but they're more obvious where there's wear or staining. 5. Concrete doesn't (in my personal experience) age well This is just my experience, but we've found the concrete to be an absolute bear to keep clean, especially in the kitchen. Every spill, particularly containing oil, risks a permanent stain on the surface unless it's wiped up immediately. Some months after moving in, my wife took the rubbish bag out of the bin in the kitchen and put it on the floor. She forgot to take it out and it leaked overnight. The resultant large and obvious stain is still there over 9 years later. There are smaller stains underneath the bin, in front of the fridge, along the bottom edge of the dishwasher, and at various random points throughout the kitchen/dining area. It's just my personal impression, but it also just feels like it's become a bit grubby over time. It's partly due to the stains mentioned above, but also the polished surface has dulled in areas of high traffic. To me, there's a difference between a rustic, "honest" finish that shows the construction method (e.g., edge/corner inconsistency and float marks) and the history of the house (general wear, such as more matte areas where the polished surface has worn down over time), and stains that just make the place look dirty. We're not super tidy people but we are quite clean, so the staining really annoys me. I don't personally see how you can avoid staining. Perhaps regularly applying a sealant would reduce the problem (we've only done that once or twice after the original sealant was applied), but the big stain mentioned above happened only a few months after the first industrial sealant was applied. 6. You might be stuck with it If you really hated a tiled or wooden floor after a while, it would be costly to replace, but it wouldn't necessarily be that difficult to break up a tiled floor or remove a wooden floor. It's potentially a real challenge to do the same with concrete. In my case, I don't know what the process for taking up the whole screed would be. I suppose we could cut down through it along walls and around kitchen units, then chop it into sections for removal. A breaker probably wouldn't be ideal, as there's anti-crack mesh, and I wouldn't want to damage the underlying structural slab and its UFH pipework. Where the structural slab is polished, it might be even worse. You're unlikely to have much space to add a different floor on top of the existing slab. In our case, there's only a few millimetres' clearance underneath a couple of the external doors, so even adding a topping layer such as a microcement screed would be challenging (quite aside from the fact we couldn't afford it anyway!). Probably the best option would be to apply some sort of industrial epoxy topper, but that really limits the end look. Other thoughts It's not all bad. In general, it looks pretty good other than in the kitchen where all the stains are. It's very easy to run a broom, vacuum cleaner, or mop over - far less resistance than even a wooden surface. This is great if (like us) you have a dog that sheds hair and drops dirt/dust around the place. It's brilliant for underfloor heating and cooling - it feels nice and cool in summer and warm in winter. Some people think the surface will feel unpleasantly hard, but I don't find that bothers me at all. We have rugs in some places to soften it out, but even without them I don't have any issues. On balance, my wife and I agree that we definitely wouldn't go for concrete again. She'd prefer wooden floors throughout. I'd prefer tiles (either large format, or possibly those wood-effect tiles you can get, although I'd want a closer look at them before committing).

From memory, the DNO can change the local voltage by switching which tap they connect to on the local transformer. I'm sure there was a member a few years ago who was trying to get the DNO to do this but I don't recall the outcome.

I replaced all of my fire/smoke alarms last week, as they're coming up to 10 years old (two starting beeping within a week of each other). Each came with an elasticated cover and instructions not to remove the cover until at least 24 hours after completion of any work involving decorating, including sanding and painting. I've put the covers aside for when we eventually repaint.

Good point. I haven't mentioned it in this thread, but I'm absolutely getting a plumber involved. This thread is more about making sure I know exactly what I want done, as in my experience, trades tend to advise what's convenient for them rather than best for you (e.g., the last time I had a G3 inspection, the plumber installed - directly onto the tank- an overpressure valve designed for strictly cold water use, presumably because that's all the local plumber's merchant had in stock and he didn't want to come back again).

Our NRV is right at the mains inlet. There's no separate NRV after the branch to the cylinder from the cold feed. It's funny you mention that. Until I did the diagram above, I assumed we had one. Indeed, I thought it was a requirement (or at least a recommendation), but from a brief review I couldn't find any such requirement. No such valve is shown in the manufacturer's installation diagram, as shown in John's post above. I was going to ask whether it's at least best practice, as this would be a good opportunity to add one. The cold feed to the cylinder is quite long and there's plenty of room to fit an NRV in the cold feed to the cylinder upstream of the expansion vessels.

Thanks John. Yes, the existing EV is right above the cylinder. I'll take this opportunity to move it to the cold inlet. Given that the water softener has isolation valves, would it be best practice to connect the EVs after the softener, so they can never be disconnected from the cylinder? Thanks.

I don't know why you found the offset being there so offensive! 😆 I could have moved the table so the offset wasn't required, but it was easier to add the offset than to undo the cell merges, move the table, and re-merge the cells. Not even close. I've figured out which one to get but I need to figure out where to locate it in the plant room. This needs a bit of thinking due to the location of the water softener.