Mike

Don't come to France then! The old partitions in my place were built with 30mm thick bricks that look like thick terracotta tiles. The chimney still is, which is crazy. Domestically 50mm or 75mm seems to be the norm here these days, and of course the sound resistance is hopeless, so there's a good market in upgrading them.

Not sure if they do the full range, but I bought mine from Dimco - https://www.dimco.eu/

Yes, if it was properly done.

+1. And you can also avoid the need for trickle vents in the windows. In that case it's the perfect time to make the building airtight. There are plenty of threads about that on here.

Rather like underpinning, cutting through the full depth of a wall, to fully replace a DPC or all the bricks should be done in short sections, so that the rest of the wall remains supported, with several days between sections. It's not something that can be done in a morning... ...so if they also used an angle grinder, rather than a disc cutter, I guess that the just did something superficial on the outside. In which case, how - if at all - did they join the plastic DPC to the portion of the slate DPC that they left deeper in the wall? I fear that they may have made the damp situation (if there ever was one) worse. I'd be looking for a different builder.

The underside will heat up whether or not there are pipes, to the same temperature as the rest of the floor (though it will loose less heat when warm, of course). If there are pipes beneath it will heat up quicker, if you don't it will be slower. On the other hand, if you - or a future owner - change the layout, or change the use of the room (I've seen that happen) they would have a cooler patch where there are no pipes.

Agree - The BCO isn't going to reject the SE's design, but does need to approve it. If it was deliberate, I'd be talking to the police about criminal damage.

Yep! +1 Also don't overlook the possibility that some of the damp may well be due to poor heating and ventilation. You may need to address those too.

There's always a risk, but the BCO is king and should - hopefully - know the local conditions. In theory would be possible to insert movement joints. I'd probably just remove any loose material, tamp down the trench bottom and get on with it, unless you have a particular reason to be concerned. The alternative would be to get a structural engineer's design that the BCO is happy with.

Welcome to the forum. Cement-based pointing 'cures' - a chemical process that can take place under water - rather than drying out. That will largely have happened in the first month. However it's harder to know whether the mix used was appropriate, or whether it was applied properly. For example the joints should have been cut back to allow a sufficient depth of pointing - if it was smeared over the surface then it wouldn't have much adhesion. But from your description I'm not surprised that the cavity wall insulation was the problem. If water penetrates the out brickwork - which it can, in large quantities in an exposed condition, even with good pointing - then it still shouldn't affect the inner leaf.

Welcome - sounds like you're on the right track! Apart from the aesthetics of concrete tiles, they are also significantly heavier than clay tiles, and heavier than the roof timbers were designed for, which can lead to sagging. I'd change them too.

If you have a low-e coating on one pane, you can shine a LED light through the glass and work out which layer the reflection is coming back from (it will have a different colour). If you specified a pane of toughened or laminated glass, then it should have a marking similar to @Kelvin's photo. Otherwise you'd need a specialist laser-based detector. I do remember some old research saying that it wasn't uncommon for units to be fitted the wrong way round. So worth checking if you can.

I last used Pro Clima Mento 1000. A company with a good reputation, but not the cheapest.

Except, presumably, clothes? That's where I'd guess they're coming from.

An interesting project, and also ideally suited to upgrading the thermal insulation throughout too. Indeed the work you're doing requires that to comply with Building Regulations, but I guess you know that if you've been talking to an architect. Lime plaster is breathable and airtight, provided it is sound, without cracks, and has been stripped of vinyl paints and papers. However you'll also need to seal all the junctions with other materials using specialist airtightness products - there are other threads on here about those. You want breathable paint, to allow moisture vapour to escape. This is a key decision. If you can afford to, stick to those independently tested for the Passivhaus Institute: https://database.passivehouse.com/en/components/list/ventilation_small (the 'efficiency ratio' is the overall measure, taking into account heat recovery + electricity consumption). Passivhaus certified units come with a more realistic measure of their performance compared to non-certified units (Paul have a short explanation). But any properly specified MVHR unit is better than none. Generally the ducting is run in the ceilings, or sometimes the partitions, so unlikely to be a problem.

It should mostly resolve itself. The tannins will leach out over a couple of years or so, subject to the weather. And likely from the render too some time after that. However, there is likely to be some ongoing staining from the rain - it's a potential problem whenever whenever rain drips off one surface on to another absorbent one. A drip bead similar to @Russdl's can significantly reduce that.

Prior to this, moisture below the floor would have been able to evaporate into the room. As this can no longer happen it will tend to build up and consequently make the bottom of the external walls damper. In other words, you've turned it from being 'breathable' - as per @Redbeard's definition above - to non breathable. Dig down outside so that moisture in the wall has the ability to evaporate to the outside, so preventing the damp from reaching floor level. As the rest of the walls are dry, that will hopefully be enough, subject to the following (and assuming damp isn't a bigger problem at other times of the year). As there's no damp where the ground level is lower, lowering the ground level is the likely fix. Though, as above, the new concrete floor may increase the moisture levels in the wall. Consequently I'd also suggest digging a little further elsewhere too, if you can, so that there's more wall below floor level from which the moisture can harmlessly evaporate. To enable the wall to breath, I'd suggest using a breathable (moisture vapour permeable) insulation - preferably a natural one such as wood-fibre or hemp insulation batts - behind your metal studs. Many natural insulations such as these can adsorb and desorb moisture vapour into their fibres - which is good (and why they're preferable to rockwool, which is also breathable). And, to maintain the breathability, you'd need to use natural paints, rather than sealing the plasterboard with acrylic ones. An alternative would be to loose the frame and the plasterboard and use hempcrete as the insulation, with a lime plaster finish. As @Redbeard says, you'd need to create the a ventilated void so that moisture could escape, as that's not the meaning of breathable, but that's not normally done. Finally, to enable moisture from the room to escape, you'll also need good ventilation.

I'd try adding some standard UFCH pipe staples. The minimum length is probably 40mm, so if you only have 20mm of insulation you'll need to staple over the pipe, though the crate and into the insulation. And you'll need to punch a pair of holes through the crate first for each staple. Hopefully the insulation won't lift too, but if it does you'll have to add some temporary bricks. I guess you're using a liquid screed - if so pouring it from the centre of the floor will also hopefully help to flatten everything and allow you to take out the bricks.

Personally I'd choose an external system, with a drained internal cavity as backup. That's mainly because, years ago, I knew someone who had an externally tanked system that leaked. It was a semi-underground extension to provide bedrooms for his kids. By the time the legal dispute was settled (solution: add an internal drained cavity) - the kids had left home.

And, if there are no other viable means of cooling, 'too much noise' may be somewhat elastic. Normally the in-room diffusers should run whisper-quiet but, in a heatwave, given a choice between being unable to sleep due to too much noise -vs- too much heat, the tolerance for noise may well increase.

I've just installed one in my French apartment renovation as I had no other viable options. However the chances are the summer may be over before it will be operational, so unlikely to be able to provide feedback soon (and France isn't the UK). There are a few useful reviews on the Netherlands version of the Ventilationland website that you can put through a translator. From my research, in theory such units should be able to drop the air temperature to within 3 or 4° of the wet bulb temperature. According to the 2005 ASHRAE Handbook, in London the monthly design dry bulb and mean coincident wet bulb temperatures for July are 30.9° and 19.7°, so nominally you may be able to drop the temperature (in the duct) to around 23 or 24°C (3 or 4° above 19.7°), which would be a useful improvement over pulling in air at 31°. However the airflow rate is a limiting factor. In my case I have plenty of spare capacity to boost the flow rate in heatwave conditions to well over 1 air changes / hour, which will help. If your unit is low end, maybe that's not an option. While not huge, the HomEvap does require a bit of space - it has 200mm duct connections, needs enough clearance to rotate it to change the cartridge (unless you have top access), and needs a drain connection. And it must be horizontal.

Skim every time for me; it provides a better quality surface. With jointed plasterboard it's virtually always possible to detect the joints when the light is in the wrong direction.

I'd avoid PIR too, for the same reason. I'd either be looking to use hempcrete, or hemp / wood fibre insulation batts.

Me too. Or use bricks set below the level of the lawn. And I'd invest in a robot mower...

Yes, example 3 is the answer - get it accepted as an art installation and skip the building regs...