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Foam just needs tidied up and then plaster, also aluplast, well done. 4000, 8000 or Energeto? Did you purchase from a UK supplier?

If you've got an abundance of time and money, then maybe............ From all the jobs I have been on where the client wanted to use this ghastly stuff it's been a painful, elongated, and expensive pursuit. In the end most give up with the FST and just plaster over it in a state of complete surrender. Life is hard enough.........why make it harder.

Drain the cylinder and stick a borescope camera in and have a look? Cheap cameras are £10 on amazon. EDIT: it's a vented tank so maybe there is something other than scale in there.

So maybe the 30 year old cylinder is showing its age and it's time to buy a new one. If you do get one with a big coil for fast reheats and heating at a lower flow temp. Maybe scale on the inside of the cylinder protected, but could just as easily be bunged inside the coil. So you could clean with chemicals. But a 30 year old cylinder the risk is yours to take.

Hi, I have an s-plan setup. I have tried setting the flow temp higher and it makes no difference, the boiler behaves in the same way with just a slight variation in the temperature that the boiler restarts the burner. So boiler set to 70c, cylinder stat left at 55c, same sequence of events as before and cylinder never reaches the cylinder stat setting or even stays on long enough to reach the setting.

Plasterboard....what's that. Real self-builders use Fermacell! But yes I've found that the multitool is the solution for the plastic boxes....needs a steady hand and concentration! Have fitted a fair few metal boxes too!

So are you on an S or Y plan? Assume you are. If so the flow temp of the boiler will be the same for heating and DHW. So would suspect you have turned the flow temp down to be efficient, but you now have a flow temp too low to heat cylinder. Set to 70 degs flow temp and see what changes

Not quite true as a large amount of installs will be fitted with BS61008 RCCB's which are all bi-directional. It's only B61009 RCBO's where the issue arises, as these are usually uni-directional unless otherwise stated. This never used to be a problem until a couple of years ago, when it suddenly became a problem. Now, it doesn't seem to be a problem anymore. It's almost like magic.

It’s a swizz, I’m sure of it. The thing is from my experience, nearly every floor layer plays the same game. I’ve done whole secondary schools with a slab poured 12 months prior, many metal rib with only 150mm max thickness, they put the probes in, it says moisture too high (especially for resilient floor coverings like linoleum) and they say DPM or no guarantee. 90% the time, it’s ok. 10% the adhesive fails and it’s a very expensive job to make good. ultimately, they don’t want the risk. I get it’s we pay because we don’t want the risk either. it’s not always the case but often. you can always tell them you will take the risk? Imho, less of an issue when the floor can breathe like timber

Unlikely to be scale as the house has always had softened water.

Sounds like scale on the HW coil in the cylinder. Descaling likely hard, so maybe time to think about a new cylinder?

Recently I have been looking at ways to improve the heating of my DHW due to my boiler struggling to heat the HWC to the temperature set on the cylinder thermostat. To give some background………I have an 11 year old Worcester Bosch Greenstar 24i system boiler with the boiler thermostat set to about 65c and a 30 year old vented HWC with the cylinder thermostat set to about 55c. We have sufficient hot water for our needs even though it never heats to the cylinder thermostat setting, generally the temperature at the taps is about 50c. The issue I am having is that in a one hour DHW heating cycle I have noticed that the boiler fires for about 20mins in total in the one hour period, the rest of the time the burner is off but the pump is continuously running. BTW I have an ABV installed which I have checked to make sure it isn’t activating. A typical cycle is…..Schedule on, boiler fires, after about 15mins the boiler turns off the burner having reached the boiler set temperature, pump continues to run, about 35mins later the boiler turns the burner on again (flow temp at approx 48c), after about 5mins the boiler turns the burner off having again reached the boiler set temperature, about 5mins later the schedule turns off and the pump finally stops. Clearly the HWC is unable to absorb all the heat from the boiler resulting in a low deltaT of about 6c between boiler flow and return. Lowering or increasing the boiler set temperature by a few degrees either way makes no difference, adjusting the flow restriction valve on the HWC return makes no difference and Worcester Bosch tech support tell me the boiler can not be range rated so am I just stuck with a poor performing boiler? I know this issue will go away once the heating season is back but I am wasting electrical energy in the mean time due to the pump running continuously during the “ON” schedule. Any suggestions on what if any improvements I can make would be appreciated, other than to scrap the boiler and buy a lower rated one. Thanks

If you must use fast fix boxes, use a multi tool to cut the hole. Then paint the cut hole in the plasterboard with PVA and let dry before fitting the boxes. It keeps the cut plasterboard edges together.

Does that mean you aren’t ventilating the cavity above the window, nor allowing moisture that sits above the windows to make its way out?

Not sure if there’s anything out of shot that we can’t see, but I’d say there’s no point putting intumescent strip above that window. Just use treated timber that’s 38mm or deeper to close it off, don’t think there’s anything worth ventilating there.

I'm going to look for the screed manufacturer's info on this. I noticed that they had about 8 products and they will all have different absorption properties. We are currently measuring the air humidity in the enclosed space of the testing box. That must be an approximation. A probe will be another approximation as the free moisture content must be linked to the amount of impermeable aggregate in it. The only real test is to take a core and heat it and measure the water evaporated off it. That isn't going to happen. The floor will be engineered timber, and the manufacturer has nothing to say on the matter. The contractor changes his requirements when challenged, as in the initial post. Wants to seal the screed or charge an abort cost, so I have no trust in them. I will be there on the day and the poor chap may have a hard time if he plays at being technical. What I don't want is them walking off because the scam hasn't worked.

47mm boxes screwed into the green OSB boards for current MBC project; 35mm battens, ~16mm PB + skim, so the box is bang on. Were doing 15mm PB everywhere here, so a bit shy of the painted surface, but much better than fast-fix boxes tbh. These have their place, like when clients can’t make such decisions ahead of boarding / skimming etc, but metal boxes should be used where you can.

I've always found that they give the correct advice and don't sell for the sake of it. That's good business too as they started with just the one passionate inventor: was it 25 years ago?

The 135 spigot connector may well be an odd size, as some have a Euro spec outlet on the trap body, then an Euro > UK adaptor to get you to 40/42mm metric waste pipe. If you can pull the spigot 135 out, try fitting a 40mm compression nut onto tye thread to see if it’s Euro > UK, or simply a conveniently supplied UK > UK offset (that can be discarded if superfluous. If it’s a UK fitment then you can just replace the conical rubber seal, but if it’s a Euro fitting then this may need ‘more research’ to get the correct replacement. If you want a simple, robust solution, CT1 the male spigot, put the existing rubber back onto the spigot, apply a bit more over it, and crank the bastard home. Leave for 3-4 hrs and test. Also check the body of the trap doesn’t have a crack in it.

What would you like to know?

Am I correct in thinking that for ventilation behind the cladding here (assuming it’s timber), you rely on the horizontal battens providing lateral air movement? (love the detail in this thread - exactly what makes buildhub so useful!)

@john0wingnut >>> how I am going to run an intumescent strip along the top with ventilation mesh Envirograf do a combined mesh / intumescent product if that helps.

>>> So do I need the windows as well as the ridge and eaves for No 3? Sorry missed that. Can’t see any reason to unless you think you might have a battle over ‘overlooking’ or need to establish some similarity to the neighbours e.g. building a new end-of-terrace. In any case once the surveyors have done their set-up, marked their stations, taken gps coords of those, recorded points say on a 2m grid for ground levels, features, fences, poles, pipes etc etc etc … a few extra points will (should) make zilch difference to the price. You may want to use the same surveyors to mark out your design, so you might ask them about that process. Also, you might like to set-up a hard-to-disturb datum level (we used scaffold poles) at a known round number absolute level. Then you can calc other levels from that with a laser whenever you need.

@Owain1602 >>> What are you going to do at the heads of the windows? We used thin stainless strip as per an earlier ‘ub discussion. Quite a bit of work, but done now. Much cheaper than intumescent of course and seems to me anything fireproof will work (maybe not in the regs though) as you don’t need the expandability of intumescent.