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Hi @kaish did you ever get around to building your shed. What did you do for foundations in the end?

Actually, just found this interlocking tile from Weinerberger Sandtoft called a Vauban that refers to the magic 168mm width as the covering width. Would this tessellate with my neighbour’s plain tiles? I attach the data sheet.

I thought I would update this thread with the latest. We now know exactly what we want in an ideal world: plain clay tile (265mm x 165mm) in anthracite grey. This will tessellate with my attached neighbour's rough as that is the size of his clay tiles, and it is also the colour we want. However, we are not living in an ideal world. Lead times for this tile, regardless of manufacturer, is 16 weeks plus. If I wait for that, my builder will probably kill me. I've looked at concrete alternatives, but as we are having a tiled roof over our porch we will see the tiles up close everytime we walk into the house through the front door and concrete tiles up close just don't look as nice. I don't like their roughness, especially on the edges. I also understand that the colour on concrete tiles can eventually fade and they absorb more water. Looking at my contract I realise I had agreed with the builder that he would lay interlocking tiles, so I imagine if I now ask him to buy and lay plain tiles he will charge me more as the whole point of interlocking is that they will make life easier for him. My question is, if I get a Redland Fontanelle Interlocking Plain Clay tile, which is both more readily available and will match the spec agreed with the builder, will he be able to tessellate it with the plain tiles of my neighbour? Here is a diagram of the Redland Fontanelle: I'm assuming the answer to my question is a big NO, but wondering if there is a way for this to join up with my neighbour's 265mm x 165mm plain tiles fairly seamlessly so I can avoid the issue identified by @joe90 as well as keeping it more seamless for aesthetic reasons. If there isn't, then I might revisit the idea of reusing existing tiles that was suggested by @keith65, even though I hate their colour, they must be at least 40 years old.

But what I don’t understand is how people use these non standard size bricks to course properly with their cement blocks? Do they get non standard cement blocks as well?

I’m just struggling to find a brick colour that will work with my scheme. It’s odd though, the sample board they sent me for these bricks is definitely regular sized bricks. But for some reason their website only shows the short ones. Fingers crossed this is just an oversight on their site. I will give them a call in the morning.

I was about to confirm my order for the facing bricks for my rear extension, and I noticed that the bricks I am about to order are 11mm shorter than the standard height of a facing brick, in that they are 215 x 102.5 x 54mm. Does this matter? Apart from having to lay an extra 20% more bricks, are there any other downsides? Will this still tessellate with a standard cement block for the inner skin? What mortar height would you recommend with 54mm high bricks?

I saw that on another thread @Onoff said that Lots on here have done away with a screed and just have a floor build up with the floor finish going straight on the concrete slab. Would that mean I would increase my concrete slab by 55mm to 205mm and do away with the 55mm screed? What are the advantages of this?

So what is better egger or caber?

Anybody have any comments on this build up of my ground floor (we've taken out the original timber vented subfloor of a 1930s semi and are going to have a concrete slab instead). Any tweaks or improvements? (I don't have any more space, so any increase in insulation would have to be balanced out by a decrease in something else.)

Yes, it is meant to be a facing brick. Not sure what you mean by weather resistant. It is marketed as frost resistant. here are specs:

Helpful, thanks. What about the crumbling corner/edges?

I’m about to order about 2800 facing bricks for our extension. After much searching, its come down to this brick (pictured). However, two things are concerning me: first, is it normal for bricks to crumble slightly at the edges/corners before they have even been handled very much? This brick was sent to me by the manufacturer wrapped in bubble wrap, by fedex, as a free sample, together with two others which were also individually wrapped in bubble wrap. On taking the brick out of the wrapping it looked to be in mint condition, but just taking the brick from one room to another and looking at it in different light it has somehow started to crumble. second, why is the facing side of the brick slightly darker than the top side (the top side being the side upon which my thumb is resting)? I asked the salesperson about this and she replied “as with every single brick on the market place all bricks only ever guarantee one good header and one good stretcher; the bricks are not coated or varnished with any coatings that is the natural finish of the facing brick” but it really doesn’t make sense to me why it looks slightly darker as if it has had some sort of sealant applied to it. I prefer the lighter side, so I’m almost tempted to lay them on their sides, but that is probably a recipe for disaster.

Thanks @Nickfromwales. What calculation do I need to do to know what size accumulator to go for and are there any particular brands and models you recommend?

Once it's finished, my house will have three bathrooms, a kitchen sink, a utility room sink and a sink for the guest WC. So plenty of outlets. We're a large family so chances of more than one person showering and also having to compete with the person doing the washing up in the kitchen sink are fairly likely. But I had thought that one could maintain pressure/flow (these are different albeit related concepts of course) by installing an unvented hot water cylinder. Isn't that the main advantage of an unvented hot water cylinder over say a combi boiler, in that a cylinder will replicate mains pressure at flow across multiple outlets? Or have I completely misunderstood that? I haven't managed to figure out my mains pressure/flow yet because I know it is currently poor, but we are upgrading the diameter of the connection to the water company's mains, so once I do that I will know for certain. But prior to the upgrade I think I was only getting about 13 or 14 litres a minute and probably a bit less during peak times. Fine for a single shower, but unusable when I was in the shower competing with the kitchen sink (though I guess that could be down to the boiler we had which was a 18kw Vaillant ecotec from about 8 years ago. Also interesting that with that boiler if you switched the heating on at the same time as trying to have a shower, the heating wouldn't come on until the shower was turned off. So useless for heating up a towel on a towel rad whilst having a shower.

thanks @Nickfromwales that’s helpful. Re your point above, what are the advantages and disadvantages of radial pipes over regular series, apart from being able to switch off individual supplies with radial? Does radial require a manifold and aren’t these quite pricy?

So if I were to do that, how does the join from a Hep20 pipe to an outlet, say a tap in the bathroom or kitchen sink, not get “hidden” and at the same time not be visible whilst one is actually using the tap. Is it concealed within a basin cabinet? What about with a shower or bath tub? Apologies, I’m a complete novice.

Okay, so Hep20 fittings and Hep20 plastic pipes seem to be clearly preferred on this forum. Two questions: 1) are they significantly cheaper than copper pipes and brass fittings? 2) does one still need to insulate the hot pipes?

Thanks @joe90 and @PeterW. I was told by a family member who has done a lot of property refurbs that plastic pipes are more prone to leak at the pushfit connections, and that whenever he has had to fix a leak it's been a plastic pipe. Now in those conversations, he definitely mentioned "plastic pipes" not "hep20". Is there a difference? I have no experience or knowledge of hep20, but I would have thought that if a mistake is made with the installation of a push-fit fitting on a hep20, it might not be noticed until the floor/ceiling is sealed up. i.e. on an initial test the loose connection just about survives and it is not until later that it fails, whereas with metal joins either its tight or its not and the plumber would see this immediately. Now this may all be just a figment of my imagination and as I say, i have little direct experience of either product. My main concern is that I don't have the ability to supervise and check the plumber's work, so I rather specify what is most likely not to fail. But maybe that is hep20.

And there I was thinking copper pipes are better than plastic. I've specified copper pipes and brass fittings. But I hate noisy pipes. Currently living in a rental place where the pipes are so loud they can wake us up. @epsilonGreedy are you saying that the floor needs to give the copper pipes space for expansion? Won't all pipe work be between the webbed gaps in the posi joists?

Thanks everyone, you've convinced me of the 400mm spacing, so will insist on that. @epsilonGreedy you make a good point about 18mm ply being damaged by weather. I hadn't really considered that. Would you recommend Caberdeck P5 instead. TP sells it for 17.88 per sheet including VAT, whereas the equivalent amount of 18mm ply would cost 24.40 inc VAT. So ply is actually more expensive. I just assumed even P5 chipboard would eventually soften up and ply would have more longevity, but I've not used anything other than ply previously, and I've never been dissapointed with ply. Except previously has always been in flats with no exposure to the elements. How do you recommend I stress test the first floor? Just walking on it and feeling it, or is there a more technical method? And does the D4 glue just go on top of the joist before the structural floor is laid onto it?

Yes, well I want no bounce really. And I'm a big guy (100kg) with big stompy feet and my wife always moans about the floors creaking. I've specified 18mm plywood flooring deck instead of chipboard because I thought that would give more rigidity and I thought that was a good thing to pay extra for, but I guess the joists are just as important. I think 400mm centres is overkill though. Surely 450mm or 500mm would be sufficient, particularly with the 18mm ply as the structural floor.

This would increase the amount of posi joists required by almost 50% (e.g. a 6m wide space would require 16 instead of 11) which seems like quite a big expense. I have about 120 square metres to cover, very roughly it's a 7.5m by 10m rectangle plus a 7m by 6.5m, so not a small amount of joists. Surely if the manufacturer specifies 600mm centres, then as long as they are installed in accordance with manufacturer's instructions, they will be solid. Or am I being naive?

Thanks @Big Jimbo. By upping the spec do you mean laying them at 400 centres rather than 500 or 600, or do you mean going for wider joists, or both?

Reading this thread is making me regret switching from regular joists to posi joists in my spec. The only reasons for the switch were various people on this blog praising the ease of installing MVHR ducting through posi joists, but that was when I wasn't expecting my builder to say that he had never worked with posi joists before. Given I will be using mainly 75mm diameter radial ducting, query whether I should just switch back to traditional joists. Won't those be thick enough to withstand 75mm holes? I really hate springy floors and want it to feel rock solid. Maybe I should have done what @joe90 did which i think was go for JJI joists, with those metal frames for hole supports, but that just seemed like extra work and at over £20 plus VAT for the metal hole support, seemed expensive. I just feel like I'm damned if go for Posi joists and damned if I don't. So given builder is more comfortable with regular joists, perhaps reverting to that is the answer. Or maybe the answer is to ensure builder studies the installation detail of posi joists and follows it religiously. He is very capable, so there is no rational reason for me to be worried I think. Is this something a Building Regs officer would monitor, or do i need to do it myself? I would ask my architect, but he hasn't got experience with posi joists either. The SE was obviously familiar with them, but not sure that sort of supervision comes under his remit. I don't think anything has been ordered yet, but it's happening this week, so not much time to decide.

@PeterW thanks for this recommendation. I gave them a call and they have helpfully offered an option for Sunguard SN35/70 glass as well, which isn't too expensive, considering these are 3G. They are also fairly reasonable for structural glazing as well. Just wondered what your experience of their external flat rooflight is. In particular, what were the upstands like and do you have any photos of the installed rooflight from within your house you wouldn't mind sharing?