Mike

Only if you bury the paper underground when you're done with it.

Why not upgrade to a whole body dryer?

Depending on the load, you may not need nail every hole; manufacturers often have load tables to enable that to be determined. Although unless you have a huge number, by the time your engineer has worked that out you could have nailed them all anyway. It's normal to use 3.75 x 30mm square twist nails, if you'd not already spotted that.

You're right; two single check valves in series = 1 double.

Do check the spec with care - non-return valves (a flap), singe check valves (spring-loaded), and double check valves (two singles in series) provide different levels of protection. I don't buy Hansgrohe, so those I've bought have only had non-return valves If a shower hose is long enough for the head to reach the water in another fitting (other than a WC or bidet), then protection is required. That is either double check valves, or a means of preventing the hose reaching the water - shower screen, fixed shower heads, shorter hose, hose retainer or, if the shower if fed from a bath tap diverter, a self-cancelling diverter. If a WC pan or bidet can be reached, then all of those means are acceptable except the double check valve, which doesn't offer enough protection (you can use a dedicated feed with a tank and an air gap, but nobody does). Which, as Jeremy notes, is somewhat strange as several of the alternatives can easily be bypassed. Seems sensible to me to always fit double check valves as a better-than-nothing backup, in addition to one of the other methods of protection.

That's a good sized tank, but the timber size sounds normal for that span, even if the load is more than normal (1.5kN/m²); personally I wouldn't be worried. And yes, the joists would flex if there were to be a problem - so without a ceiling beneath not such a big issue.

Don't do that; drainage pipes should normally be bedded and surrounded on as-dug material or pea gravel to enable the pipes to flex with ground movement, rather than cracking. Check out the installation guide for the brand you're using.

That's what I'd do, and have done in the past.

+1

The ramp looks reasonable, though not generous - for a car. However if you have a guest park on it, there wouldn't be much space to walk past. The cars you've drawn scale at around 4.65m long, and that's not very generous either - a Ford Focus is around 4.4m, a Mondeo nearly 4.9m. Finally, depending on your local authority, you could have problems with the garage - both because it's also not overly generous in size, and also because some LAs impose restrictions preventing their conversion for other uses, which you seem to be planning. You may need to be a bit more generous all round.

There are low-profile ceiling hung units (e.g. Brink Renovent Sky 200, Nuair MRXBOXAB-ECO-LP2) and units with dimensions to match kitchen wall cupboards (Vortice Vort HR 200 BP, Nuaire MRXBOX95AB-WM1, Zehnder ComfoAir 180) that might work, subject to your air flow requirements (which might be too high for a single unit, if you have a 3-floor house). Zehnder's ComfoPipe Plus twin duct range is also designed to fit along the top a row of kitchen wall units before connecting to their 70mm high flat distribution ducting.

In fact I'd also consider the door handing for the 1st floor doors in general.

Agree with ProDave, particularly about finding out what level of airtightness they can guarantee you. Also, might be worth looking at the possibility of fitting a MVHR system, if they're not too far advanced.

A few things to consider: Ground floor: Not convinced by the wood burning stove. Having one side (the back?) opening into the dining area, rather than the living area, isn't ideal - there won't be much to see from one of the sides, unless you're splashing out on an architectural or double-sided stove. You also seem to have a door into the snug, but can't shut off the space as the stove area connects the snug with the dining room. The location of the log store implies that the stove will be fed from the dining area, rather than from the snug - whereas I would guess the stove may be facing the snug? And Do you really want that many logs stored, below what I presume would be the 'TV wall'? I'm not convinced that the larder would give as much space as you might be imagining, by the time you've allowed access space within it. Would it be better to have another full height 2 kitchen cupboards, plus a separate smaller store below the stairs? You need a minimum 100mm step up from the garage to the house, for fire protection. I'd hang the utility-garage door to open against the blank wall, rather than blocking the cupboards. 1st floor: I'd add a 3rd door to the middle bedroom wardrobe, so the full width can be easily accessed. Open up the space fully between the staircase and the lightwell / void? Including, perhaps, getting rid of the store. Adequate sound-proofing between the family bathroom and the guest bedroom?

Most vapour-permeable sarking membranes have agreement certificates that enable them to be used with no ventilation gap between the felt and the insulation, and no ridge or eaves vents either, provided there is a vapour control layer on the inside of the roof / ceiling. Solitex Mento, Tyvek Supro, etc.

Raising the garage floor level would be another alternative - the Building Regs only require a 100mm step.

Building Regs Part H would be a good place to start.

Yes, there are plenty of timber frame houses that have very good airtightness - to PasivHaus standards and better. Various other threads on here talk about the topic. MVHR is certainly 'worth it' once you have good airtightness levels. Financially you'd need to calculate the payback period, but I think it's worth doing anyway for the enhanced air quality and to avoid the need for trickle vents.

Cheapest way would be to unscrew it from the wall - there may be some identifying information on the back to enable you to check out the spec.

Sounds like you need to take professional advice. If you're developing for sale you'll be liable for either income tax & NI contributions, or corporation tax, depending on the way you do it, quite apart from the VAT issue...

In some parts of the UK it's necessary to have a sump too, which could be behind the decision.

On the ground floor the main drawback is the use of the kitchen as a corridor through to the living room and to the back door, which limits the usefulness of the lower half. Difficult to do much about the living room, but access to the back door could be closed off as you already have a route via the utility room. You could look at rearranging that space, as ProDave suggests. Upstairs I'd check the sound proofing, particularly between Bed 2 and the bathroom, and between Beds 3 & 4. You don't seem to have provision for a MVHR unit?

In the course of investigating my own requirement for cooling - - I did come across the Unico Boiler that can do something similar on a small scale, if the heat pump version is chosen. It's a through-the-wall 2.5 kW unit (requiring a pair of 160 or 200mm holes), not very pretty, that can either chill or heat the air, as well as heating a 50L hot water tank (which takes priority over the air treating). I get the impression that it's more targeted at the southern European market and haven't followed it up any further yet, though I may. However at 2,700€ it's not cheap, but maybe there are better deals around. The manual is available to download from here.

Have you come across Postsaver bituminous post sleeves? Would be less hassle than building a concrete wall if they work as claimed. I used them on a new fence last year so will report back in a decade or two...

Since it's on topic, despite the big gap, thought I'd feed back that there are at least 2 companies in the MVHR business selling filter boxes that take carbon filters; Zehnder's NOx filter, and Blauberg's CleanBox (which also provides NOx filtering).