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The side wall of our semi detached 1930s house is made from a double thickness solid wall on ground floor and a single thickness solid wall above that. This wall, predominantly the ground floor, but also some further up, was diagnosed with damp at the beginning of winter. It has been damp for a couple of years as when we bought the house in 2018, damp came up on the survey. The surveyor who looked at it in December last year identified various issues causing the damp, predominantly 1930s pebbledash not being great for walls, the pebbledash itself having lots of cracks, the DPC being too close to the external ground layer, inadequate drainage, various cracked downpipes. We have taken off all the pebbledash, dug a trench to install an aco drain and are planning to improve the wall by affixing 40mm K5 insulation externally and then rendering over that. All drain pipes will be replaced as well. The insulation will stop the breathability of the wall on the outside, but to mitigate that we are using a fully breathable build up internally, with a ventilation gap. The surveyor is happy that this will be a good solution but would like us to dry the wall a bit more before doing this. His "belt and braces" solution for drying it was to install a temporary render on the outside (instead of the K5) that will draw out the moisture and then take it off after a couple of months and then do the K5 and finished render. This is quite expensive as it effectively triples the labour as well as adding material cost. As an alternative, he suggested we hire some large dehumidifiers and run them for a couple of weeks. The difficulty we have is that we are not air and water tight yet, so I don't think the dehumidifiers will work well until we are. Most of the windows are in, but they've not been sealed yet and there is a large 4.3m by 2.1m gaping hole at the back of the house where we are still waiting for the sliding doors from Sunflex. The wall is on the side of the house in an alley way so doesn't get much/any sunlight, particular at ground floor where the damp is worse. My builder has a large space heater, a bit like an industrial sized hair dryer and I was just wondering if it would make any difference if we blasted the wall with that for a few hours a day for a week? It would surely heat up the bricks and allow the moisture to evaporate, but could it damage the bricks in any way?

"Boundary of the property" is different to "property" because the latter is a little ambiguous in that it could mean several things, from a chattel to real property, whereas the former is quite clear that it is referring to real property (i.e. land) and not to any building on the land. "Boundary of the property therefore means, in the strict sense the boundary around your land as shown on the title plan. Now whether you count that as your sole land or also including the shared ownership bit, is a bit unclear and I agree with @IanR that if one interpretation over the other suits you best you argue for that one, as they are both arguable. Where I think you are on less strong ground is in respect of the portion of driveway that you don't own at all and just have an easement of access. That is not your property at all and certainly doesn't fall within its boundary.

Are you serious? On the pitched roof, I think the neighbours would complain to the council and I would get in trouble. But on the flat roof on top of the loft conversion, that is probably fine, as long as it doesn’t affect the performance of the roof covering, which I think will be GRP - assuming that is the standard covering for a loft conversion’s flat roof???

That was my plan, but in this thread you had a look at my roof and didn't think PV would work well. We are using a heat reflective membrane/felt within the roof build up, something made by Tyvec, which is meant to be quite good, but I'm not sure it will actually work. I hadn't considered a reflective coating though.

My build up for the walls and roof includes a layer of 40mm Steico Protect dry internal wood fibre board. This is out of stock with all the merchants I have approached (Mark Wye, insulationsuperstore and ecomerchant) and most are quoting very long lead times of up to 10 weeks. Can anybody suggest an alternative which would have the same decrement delay properties. Someone has suggested Phenolic Foam based product Kooltherm K7, made by Kingspan, on the basis that it has a density of 200kg/m3, but I don't think it will have the same decrement delay just because of the density. Any thoughts?

Now managed to have a play around with a calculator and figured out that if we fill the rafters fully with soft wood fibre wool, and then add PIR below, we will meet regs for heat loss and manage a decrement delay of 9.15h, although the solid wood rafters probably won't keep the heat out as much as the soft wood fibre wool in the voids in between, so not sure how accurate that 9.15h measurement is. Assuming it is more or less accurate, is that enough to be comfortable for the type of bedroom I describe above, or should I add an additional layer of wood fibre below the PIR to try and hit 11h or even 12h decrement delay? This would compromise head height, but it might be worth it. Was hoping @SteamyTea might share his thoughts on this as I think he's done quite a bit of research and experimentation on this.

Anybody aware of any other free decrement delay calculators?

I have what i think is known as a mansard roof over our first floor extension. It is flat at the top and then has a pitched perimeter along the three sides (on the fourth side there is no roof as that is where it adjoins our house). We had planned on a warm roof, but it's looking like we don't have space due to some design changes that we need to make. The rafters are 175mm. Area of room, which is a rectangle is about 4.3m long by 3.75m wide. Half of that floor space (half of the 16.125 m2) is in the extension and the other half is in the first floor of the original house, with a second floor above it. So although the majority of the external walls are brand new cavity walls, there is a 2.1m bit of wall that is just solid wall with 40mm of K5 insulation on the outside. The flat part of the roof has a large skylight 900mm by 1800mm which has solar control double glazing SN70/35 (g value 35%, U value 1.0). The only other window in the room (about 2.2m by 1.4m) is made from the same glass (g value 35%, U value 1.0) We were hoping to use wood fibre to increase decrement delay of the roof so that overheating is minimised. My architect wasn't entirely sure this was necessary as although the outlook of the room is west facing, until about 11am, possibly later, the majority of the roof will be shaded by the large loft conversion on the floor above and the neighbouring house. But with afternoon sun, that might still make it uncomfortable in summer. But with switching to a cold roof, with insulation between the rafters, I only have 175mm of space for insulation. My architect is checking to see if 100mm of wood fibre plus 75mm of PIR will meet regs. If not, he says we just build up the inside with additional PIR or insulated plasterboard. But I know regs only care about keeping the heat in, not keeping the heat out. Anyone know how much wood fibre, when used with PIR, is needed to have a decent impact on preventing (or delaying, to use the decrement delay terminology) heat from coming in from this type of situation? I know I should do a proper model, but don't know where to start with that. Alternatively, is there a wood fibre product that is rigid enough to be used on top of the rafters and double up as a structural board for the roof covering? I don't have a lot of space, but could maybe squeeze something in.

@PeterW you are a genius, thank you. Not sure why that size isn't available on the sites I was looking at.

We have removed the pebbledash from a 1930s semi and had planned on installing 40mm of external rigid board insulation onto the brickwork which we have exposed, and then rendering over that. Kingspan K5 is a phenolic core which is faced on both sides with glass tissue (more details here). Problem is it comes in 20mm and 50mm, but not 40mm. 40mm is already making things a bit tight in terms of keeping the original features of the house, but we can just about make it work. 50mm would be too much though. Can anybody recommend something similar to K5 that comes in a 40mm thickness? I don't think PIR is an option because that tends to be foil faced making rendering over it not really an option. We could use two lots of 20mm thick Kingspan and just fasten the fixings of the outer layer through the inner layer and then onto the underlying wall, but it is effectively twice as much labour, so I rather not do that.

I'm not keen on ASHP because of the noise and unsightlyness of them and the requirement in our area to get planning permission for them. A solution to most of these problems is to go with a super expensive unit like an Oschner, but even then they require a lot of space for the internal compressor which we didn't really have unless we severely compromised our utility room. Next house. The Solar Thermal idea however might work quite well for us. How much do you think that would cost? We have quite high hot water requirements (our UVC is going to be either 300L or 400L in size).

Thanks @SteamyTea, here are some drawings. The first drawing shows part of the roof plan. The dimensions are about 8.2m by 3.15m; I'd forgotten we had to make the dormer slightly smaller - for reasons I won't go into to). The ridge line is centred with the chimney stack (shown as a rectangle with 8 circles in it). The second drawing shows a cross section. You can see the pitch of the small piece of pitched roof between the flat roof and the ridge line is 45 degrees. But the diagonal length of that bit of roof (i.e. the hypotenuse on the cross section) is only about a metre, so I'm hoping there won't be much shading from that. Obviously the chimney stack will cause a bit of shade, but there isn't much we can do about that as we use it and it is also jointly owned by our semi detached neighbours.

@delta9 I really think you should: 1) find a good mortgage broker with experience of these transactions; and 2) speak to the specialist lenders that focus on the sector of the market. Both should give you useful info for free.

It’sa flat roof, ie the lid of a dormer. Hasn’t been built yet, so possibly time to reinforce it if necessary.

No, I was hoping to get those moving mounts that track the path of the sun as the back of the house faces west and the front of the house east. Not sure if they are expensive though.

Incidentally, I bought a vitra concealed cistern/frame and matt black flush plate for the very reason that matt black will work with our colour scheme (all our windows are matt black framed) and vitra seemed very good value. I didn’t have the confidence in Vitra to buy this brand for all the toilets though. Have gone with them just for one toilet that won’t be used as much as the others. @tanneja to answer your question, @Temp used his skills to find me some more affordable brass effect plates in the Grohe range from this website: https://insani24.de/ I ordered two a couple of weeks ago. The website is a bit weird because after ordering I didn’t get a confirmation email, but when I log on to my account the order is there. It was meant to dispatch a couple of days ago, but for some rain it hasn’t, so I actually emailed them today to check what’s going on (your message reminded me - thanks!). It looks all legit, so I’m sure it’s fine, I’m hoping it’s just a couple of weeks till I get them. I still haven’t ordered the Grohe cisterns/frames yet. Thinking of going with the new model that comes with a flow regulator, though I’ve never been an early adopter of new technologies, so seems a bit risky. Just appealed to it by the fact that you can tweak the flush flow rate to work perfectly with any rimless toilet - I’ve probably just fallen for the marketing!

Yes, well this is why I don’t like the idea of a thumb turn! Having said that, our letterbox is a through the wall one with a lockable security flap.

The reason I’m against a thumb turn is that our door is like this. As you can see, it is mostly glass. So although it is PAS24, and the glass will therefore be laminated, my gut is telling me that a burglar looking through the glass could see that behind the steel lockbox is a thumb turn, and that might inspire him to try to break the glass to get in. I’m not sure he (or, let’s be egalitarian, she) would actually get in, but as good as PAS24 is, it is not perfect. i can design the door to have a wider lockbox, so more of the thumb turn is obscured by the steel, or I can just lose the thumb turn and ensure there are spare keys in a place that everybody can find easily in a fire. Thoughts?

So how does one go about doing this? I will have scaffolding up in a couple of months when the loft is converted so good opportunity to do it, and hoping to put PV panels on my flat roof (above the dormer conversion) which is about 8.5m by 5m. Got a couple of quotes from companies that also install and it was just crazy prices.

Good news: the BCO has backed down and admitted that “on reflection” there is no requirement for a thumb turn.

What multiplier did they give you?

You need to find a cheaper broker! Mine charges £260 per transaction, and only after you have an actual mortgage offer. Pm me if you want the details.

So what’s the solution when I have gone to the expense of going with a private BCO and he is being a complete twit?!

I’m wondering whether these actually work well in practice. Chipboard doesn’t sound like it has the right properties to deflect heat upwards, or is the idea that you install spreader plates onto the pregrooved chipboard.