Jeremy Harris

Thanks Nick. It was a question that came up during a discussion about low temperature UFH, and both Karndean/Amtico had said no higher than 27 deg C. I'd already given a reassurance that there's no way that the floor would get this hot from the UFH (it's a build similar to ours) and that I thought it'd be OK as our floor never gets above about 23 deg C. I just wanted to check with you, as this person's flooring supplier was a bit twitchy about laying this stuff over UFH, which is fair enough if they are only used to conventional systems at high temperature, I suppose.

I used the contact page on the BGS website and they sent me a copy of the form to fill in and send back to them, together with any other data, like the water analysis or the hydrogeological report. When I enquired as to why our borehole wasn't showing on the viewer (the local council wanted the BGS reference to tie their water analysis results to), this is the reply I had back: The email address I received the above from was: ngdc@bgs.ac.uk

What's surprising is taking a walk around and finding them. I've found about 2/3rds of the boreholes within half a mile of so of our new build and only one is still in use, by a local farmer to supply his cattle drinking troughs. One of the local ones is now underneath the kitchen floor of a new bungalow...................... The old village artesian borehole is now a nuisance, as the cast iron pipe has broken somewhere and water now runs across the lane at the junction about 50m in front of our new house. The result is that the road surface is constantly breaking up and the water running over the road freezes in very cold weather. No one seems to own it any more, so no one will take responsibility for fixing it. I've been up and looked at it (the borehole is maybe 100m away from us) and it's clear that it's the source of the water. I don't think the fix would be that expensive, it'd just be a matter of digging up around 40m of bridleway, taking out the old cast iron pipe and laying a new bit of MDPE, either to the old standpipe or as an underground drain to the brook. Cornwall had loads of working private water supplies not that long ago, as mains water was really only available in the towns. The pumps on some of them are works of art. Mother's has a large (around 3ft diameter) cast iron wheel at the top, that was once driven by a flat belt, possibly by a wind turbine (Amos Pumps in Wendron used to manufacture them, US-style, and there were still loads around down there 40 years ago). The big cast iron wheel has a crank on it that is connected to a load of articulated iron bars, connected to a series on lift pumps, to get the necessary lift from however deep the thing is (it's pretty deep, as her farm's on top of the moor). The whole thing looks more like mining engineering that normal well stuff, but that's probably because of the strong mining engineering heritage in that part of the world.

Ours was flatter over the longest length that could be measured (about 10 to 12m or so) than the accuracy that a laser level could detect, so better than around +/- 1mm (laser level accuracy is usually +/-3mm over 30m). We (or rather our floor tiler) spent around 40 minutes trying the find the high spot to work his levels from then gave up, concluding that there was no high spot that he could find. In practice the combination of timber deflection and the DPM deflection may well take up 1mm, and anyway I doubt if anyone really levels a frame to better than a mm along any one side, so if it's been wedged up to make it level it's fair to assume that the error is several mm, and it frankly isn't hard to get a foundation level to better than that.

I have a feeling that the ruling may be per location, rather than per borehole, but it'll be buried away somewhere in the EA stuff, I'm sure. You could get lucky and find they allow 40,000 litres per 24 hours from a pair of closely spaced wells, but I suspect not, as the rule was intended to prevent commercial users from abstracting large volumes of water without an abstraction licence. There are thousands of boreholes around, many now disused. Our village has around a dozen, many drilled during WWI when there was a large army training camp just outside the village. People forget that in rural areas wells and boreholes were the primary water supply until around the 1930's, when mains water started to be run out of towns and cities and into rural areas. Mains water arrived in our village in 1934, but the old village borehole and standpipe still exists. The standpipe is down by the brook, around 4 or 5 metres below the water table and the old borehole is artesian, i.e. it is under pressure at the surface, so it was capped with a cast iron plate and a pipe run down to the standpipe - no pump needed.

Yes, you could do, or just do a decent job by either getting the foundation flat in the first place or by laying a bed of sealant on top of the DPM before placing the sole plate down. It's primarily a poor workmanship problem, one that's annoying because it's awkward and difficult to fix afterwards. It's not difficult to get a dead level foundation, it just has to be floated off level. This is done all the time: our entire slab was floated off dead level, so it's not exactly hard to do.

Provided you don't abstract more than 20,000 litres per 24 hours period then no, they are not regulated at all. Anyone can drill one and draw up to that amount of water per day out without needing to get any permission from anyone. There is a requirement for the driller to notify the British Geological Survey and provide them with a drilling log, but our driller failed to do this so I sent the BGS the data myself, only recently as I was browsing the BGS borehole map and noted ours wasn't on it yet. You can browse the borehole map here: http://mapapps.bgs.ac.uk/geologyofbritain/home.html and select "borehole scans" at the top left. You have to zoom in to see borehole positions and each will have a number and a reference that if you click on it will bring up whatever historical records the BGS holds for that borehole. I've just checked at it looks like the borehole record I sent them a couple of months ago is now on line as borehole reference SU02NW24

As I understand it, it is the gross internal habitable floor area, so the area of all the internal floors inside the external shell. Non-habitable area is subtracted, so in our case the "loft" space down the eaves is subtracted, as the first floor is in the roof and so has a smaller floor area than the ground floor. Space taken by internal walls is not normally excluded, though. In our case we have 75m² of gross internal ground floor area plus 54m² of gross internal first floor area, with an external footprint that is around 86m². This is why I'm concerned about ensuring that the VOA use sensible data, as if they just use the external footprint and use their normal rules to calculate the internal volume they could easily assume that it is around 150 to 155 m², rather than the true figure of 129 m². I've done our costings on the basis of 130 m², as at the time I started doing them I hadn't refined the true gross internal floor area as built. We are now at around £1380/m², a bit higher than I initially predicted, but we've added a few things that pushed the cost up. I budgeted on £1300/m², so being around 6% out doesn't seem too bad given what we see on the TV house build programmes!

There's water pretty much everywhere underground, far, far more of it than many realise. Drill a hole anywhere in Southern England and you will find at least one, probably two or three, aquifers. The key is knowing how deep it is and whether it's likely to be drinkable without a lot of hassle. We're far more fussy about drinking water that we used to be, as we've learned about shallow wells being a source of things like e coli, so it's normal now to drill down to a clean aquifer and seal around the borehole to keep surface water out, so that the risk of contamination from faecal coliforms is reduced. Our cost of getting a mains water connection was around £23k+, so I opted for a borehole. It was a fair bit of hassle, and delayed our build by probably around 12 months overall, but still a lot cheaper than a mains connection. The cost for ours (all price ex-VAT, as this was a zero rated job for a new build) broke down as: Cost to mobilise drill rig to site: £950 Drilling cost per drilled metre: £47.50 Cost of screen, casing, glass filter media, bentonite grout, per drilled metre: £37.50 Cost of Mud Puppy and tanks (used for wet drilling with mud): £675 On top of that you have to add around £700 for a decent submersible pump, maybe £150 for a well head chamber, around £100 for MDPE pipe and fittings, plus the cost of whatever size pressure vessel you need, plus the pressure switch. You may also have to include a filtration system to remove stuff like iron, manganese, hydrogen sulphide etc from some ground water and if the water tests positive for even a single e coli per ml then you have to install a disinfection system. We have a UV tube system to disinfect ours, even though it tested OK, as it is very easy to accidentally contaminate a private supply. If you just want water for irrigation, then try using the US method for driving a small bore irrigation well. They use a spiked galvanised pipe with a conical screen on the end and either just impact drive it into the ground our use hydraulic or pneumatic drilling. The former is easy, you just connect a hose pipe to the drill pipe, fit a tee handle on the top and let the water do the drilling for you. You push down on the pipe and the water washes out the much as you go. There are YouTube videos showing how they do this, its a common procedure in some area, usually where there's a sand aquifer (these are sometimes called sand point wells). Sometimes they just pound these wells in using a hammer, or even road drill, threading extra sections of pipe on as needed.

As above, it is essential that any gap, however tiny, is filled. The last thing you want is water vapour freely moving in and out under the sole plate and condensing into water when the conditions are right. This is pretty much what caused so many early timber frame failures in England back in the 70's when a mass builder started building timber frame houses without understanding the interstitial condensation risk. Some didn't even make it to the end of their 10 year warranty before the frames started rotting out.

Use a listening rod. It's a rod around 4ft long with a cup on the end that you stick over your ear. Poke it on the ground along the run of the pipe and you'll be able to pinpoint where the leak is. It's what the water company use, believe it or not. It works a bit like a stethoscope. You can probably make one. The ones I've seen have been something like a fibreglass tent pole, with a hard rubber disc on the end you hold hard against your ear.

I'd have to say it's not at all common, it's very bad practice. Our build is a timber frame and was fitted to a proper foundation that was laid absolutely flat. Anyone laying a foundation for a timber frame building knows that the foundation has to be dead flat and level, it's been common knowledge for decades. There really is no excuse for poor workmanship that can have such serious consequences on the life of the building and for the thermal integrity. Having any gap under the sole plate is wholly unacceptable, especially as filling and sealing such a gap post-erection is both very difficult and unlikely to be 100% effective. Best to try and get the sealant to totally, 100% (absolutely no voids), fill the space between the sole plate and the DPC. It'll be a pig of a job to do well, and will probably need some thin nozzles fitted to a decent foam gun to ensure there's half a chance of getting LE foam right into the slimmest gaps. Any gap at all, no matter how small, will act as a condensation locus when external water vapour moves in through it, and the impact is that the sole plate is likely to remain damp in any such area, with the inevitable risk of rot.

Thanks for reminding me about the assumption of internal floor area based only on the external ground floor measurements - it's reminded me to make sure I give the VOA as much verifiable evidence as to the true internal area as possible. Worth noting that they are still working off the rules that are in the very old Rating Act as far as sizing for valuation is concerned, so this means they assume 1969 (IIRC) wall thicknesses, unless you can make them take into account your much thicker walls.

Just goes to show what a bit of heat does to a fluid that expands yet is (to all intents and purposes) incompressible!

This needs to be a really good sealant to make that joint 100% air tight - frankly I don't like the idea of there needing to be packing under there anyway, as it's asking for poor airtightness and indicative of a foundation that wasn't properly laid. It also means that the frame is putting point loads into the foundation, rather than having the load evenly distributed. You need to seal this gap up to absolutely, 100% stop cold air getting in under the sole plate from outside, anywhere, as that risks cooling it and causing interstitial condensation from vapour movement that could, in time, cause the untreated timber to rot. Can you get at both faces of the sole plate? If so, then injecting low expansion foam as deeply as you can get it, from both sides, may be an option. It's going to be fiddly to do, but you are where you are so have to deal with this somehow. After injecting low expansion foam and after it's cured, then sealing the remaining edges with a decent quality PU or MSP sealant will stop moisture penetrating the foam (the foam is fairly air tight, but will most probably be vapour permeable).

There isn't in mine, either. I still had to comply with it, though, as it's now a bit of legislation. It was passed into law in 2010, although it's fair to say that local authorities have not acted swiftly to set up the required approval bodies. However, I found that building control dealt with it as a part of general drainage, and wanted to see that whatever we installed was SUDS compliant, even though there was nothing on our planning permission about it, apart from a mention in the D&A by me, and the D&A doesn't seem to have been referenced in our decision notice, so is non-binding (something I thought was a bit curious). As always, it will probably come down to your building inspector as to what they want to see to handle surface water drainage. Some may want full SUDS compliance, some may not; it's probably just pot luck which you get.

Thanks for pursuing this, as we're seriously interested in the same setup (and I've registered an interest with Andrew a while ago). It seems to me that the cell pressure release issue is very minor, as the volume is low and the likelihood of it ever happening is miniscule, a far, far lower risk than with a conventional sealed water heater. It wouldn't surprise me at all to find that, with time, there might be a change to the regs to accommodate systems like this and remove the need for the cell PRV altogether. The consequences of an over-pressure event are not serious, either. My view is that it's mainly a case of regulations that are worded (very wisely) for conventional unvented systems, but that really aren't wholly appropriate for this system. Nice to hear that Andrew's view is the same as mine, that an additional pair of cells should be in series/parallel with the existing pair of cells. When I was looking at the hydraulic diagram this seemed the logical way to increase the capacity, to me. It looks like feeding a flow and return from the cell circuit out of the case and connecting to the flow and return of the new series connected pair of cells should be quite straightforward. The only issue would be dodging the vacuum panel insulation and it would probably be necessary to include an additional air vent to bleed air from the new pipe loops. Another possibility that comes to mind would be to fit a ball valve (hand operated or motorised) to select whether or not the additional cells were to be used. For example, in winter, without much PV, I'd probably want to cut the storage down to just that which I could heat with a mix of PV and a timed boost. In summer, or if we had guests and needed more capacity, I could turn on the additional storage and allow that to be charged. As far as the Sunamp controls are concerned nothing would change, as it uses temperature as the indicator of state of charge and for control. I need to have a bit of a think about this, but my gut feeling is that it could be useful to be able to switch the capacity easily.

Ours came with the option of a similar ground anchor kit, as an extra. Form the description it sounds very like the one you describe, galvanised angle iron and chains: Because our unit was going to have it's lower 1/3rd below the local water table I was a bit concerned about the possibility of corrosion (and I may be paranoid, but having witnessed a Klargester "onion" float out of a field I wasn't taking any chances!). When I spoke to the manufacturer they said they had moulded in lugs that could be embedded in a concrete ring anchor, as an alternative to using the anchor kit. It was a bit fiddly, as we had to hold the tank up in the air with a digger as a crane, whilst barrowing in concrete around the narrow slot around the tank, then lowering to its final resting place, pumping water into it to get it to sit at exactly the right level. There was a layer of gravel under the concrete that the pointed bit of the tank base was resting in, with the concrete ring above this.

Bear in mind that, with no air anywhere, there may well be a marked variation in pressure with temperature. Water volume increases with increasing temperature above 4 deg C. Because of this the pressure will vary, as it's a closed system with nowhere for the additional volume to go (except the air bubbles that will inevitably be in there somewhere at this stage). Odd things happen when you dissolve gasses into water as well (which is what will happen with an initial fill like this). Ideally any pressure test like this needs a near-constant temperature. There is another effect too, caused by the way concrete contracts slightly as it cures. This is useful, as it causes it to grip reinforcement very tightly, but a nuisance when you have pipes running through it and are trying to measure pressure, as the pipes will be squeezed as well. This means you can see a slight pressure rise as the concrete cures and very slightly compresses the pipes. I'd not take too much heed of any variation in pressure measured between pre-pour and post-pour. It's likely that there were temperature variations, and the effect of the concrete initial cure, that have messed up the readings. Best to do the test when conditions are stable. FWIW I didn't bother with any pressure testing at all. I took the view that the pipe was pretty tough, there were no joints anywhere and a visual inspection would be fine. I used the same philosophy as when laying MDPE water pipe, where the chances of the pipe itself developing a leak are so close to zero that it's commonplace to not bother pressure testing it before backfilling trenches.

It may well be asbestos-free if it dates from the 80's, as I have a feeling that it's only the older stuff, before we became as aware of the risks from asbestos, that had fibres in. Probably best to just get back to a sound surface (removing the dodgy tapes and any loose stuff) and then just get it skimmed, I think.

As Ferdinand says, adding skirt insulation can be a significant help as it pretty much totally removes the edge losses, With a renovation, where there will be little insulation and not much hope of a cold-bridge free wall to floor junction otherwise, this can make a worthwhile difference, just by reducing the rate of heat loss around the periphery, My guess is that this may well make up for having less underfloor insulation.

It may well be laminated - I'll try and read the markings and report back.

It might be an idea to minimise the risk of any rippling from expansion.

Ours have 6.4mm thick toughened glass on the inner pane, and the same reduction in gap, so my guess is that 6.4mm might be a standard thickness for toughened glass (but I've not checked).

If this is old artex, then take care, as the old stuff used asbestos fibres for added strength, so don't sand it, or if you have to, wet sand it and use protective gear. I've not tried, but have heard that artex can be steamed off, and, if it works, then this might be the cleanest way of getting back to a good surface to then repair. Skimming over the artex won't be as easy as skimming over a smooth surface with scrim tape over the joints, I think.