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I have made a bit of a sequencing error with my airtightness strategy. I had planned to use a liquid membrane at the ground floor slab to wall junction before the insulation was laid and screed was poured. I neglected this and the 175mm insulation and then a latex screed with foam perimeter was poured. I am dot and dabbing so wet plastering cant help me. Can I use a liquid membrane to seal the finished screed to the wall? There’s the annoyance of the foam perimeter strip to get over and the plastic sheet under the screed would need trimming right back as currently that’s been left long lapping onto the block wall by couple hundred mm. Am I good to just try and seal this junction with liquid membrane (soudatight lq prob) as best I can?

Hope you had a fun time toooo! These sketch drawings are very good! Well done. In terms of the daylight to next door you're allowed a certain reduction before it becomes material. It's somewhere in the docs I think. The overshaddowing of the neighbours doesn't seem to be much of an issue, yet to see the rear elevation, I suspect that may well be ok. Your house is significanlty lower. This is a good observation. But the houses are still well separated and you're proposed new roof still significantly lower. If you project a roof line of the terrace down the hill what you are proposing is stil below that. If push comes to shove you could set back the face of the extension a little and / or tweak the roof so the gutter is a little lower than the main house, makes it more subservient / less mass. Usually 1.0m is accepted but I would go for 500mm if pressed as a first offer. Don't offer this up to start with, stick to what you want. If you can sketch like this then have you thought about doing you own scaled hand drawings and submitting a planning application under your own steam? This at least will let you see, what if any, concerns the planners may have and leaves you in full control over the design process at your end. If you do your own application then there is other stuff you need to submit, but that applies in all cases. Here is a quick, but not comprehensive list of things that help build a planning application like this. 1/ A site location plan, OS or say from UK Planning Maps etc, main thing is that it has a copyright number, address and a grid reference. 2/ A block plan showing the site and as you have trees you need to identify these, both within and adjacent your site. Also hedges, fences and heights. I often do a little table and annotate the drawing. Also show existing parking and proposed parking provision, bin storage area and access (also width) to rear garden. The block plan should also show the neighbours with some basic dimensions where the planners might be interested.. You also need to show the garden area and that there is sufficient garden (curtilage) left after you have built the extension. You'll find a guide in the permitted development (PD) guide. In this case you may need to do a block plan on elevation similar to what I posted earlier. Like this: 3/ Site photographs. 4/ Drawings as a minimum. All existing and proposed: Elevations, ground and first floor plans with the rooms annotated, associated with parking provision not least. A roof plan with the roof slopes indicated. Make sure you add a drawing title box, scale bar, a north point on the plan drawings and identify each elevation clearly. 5/ Some water boards are a bit touchy about adding a roof area and connecting the rainwater run off into the existing drainage system. Do a bit of research on this and keep your findings under your hat for now. 6/ Try not to be overly helpful and avoid highlighting things that "might" be debatable say if you were trying to argue some wierd technical planning detail down the pub. Let the planners do their job and come back to you with any requests for more detail. If you fancy doing the drawings yourself then you'll get loads of tips on BH about what and what not to do and, also how to avoid excessive work.

Or thickness? Cheap addon options for conventional radiators exist on Amazon (or other) and do work to a degree, but they won't perform miracles. Another option to think about is if you could replace the radiator with a proper fan coil unit with thermostat control. You could likely greatly increase the output from the space your existing radiator uses assuming there is a similar sized fan-coil available. Not cheap though.

Yes, the white is efflorescence caused by the deposit of salts from the brickwork onto its surface as the moisture evaporates. Efflorescence is harmless but can take a very long time to disappear. It may also appear damp as the salts themselves can absorb moisture from the atmosphere. Bush it off every few months or, if you prefer, buy an efflorescence remover (a mild acid) from your local builder's merchant; it may require more than one application.

@tanneja hope you are still on the forum as I have a few questions. Did you buy the buffer and do you have any tips on keeping the floor clean? Does it need an annual clean and reseal?

Glad you got it sorted @SelfBuildSmurf . I have the build hub UFH stapler ready to pass on to who needs it.

I have recently used both types of expansion foam with and without the skirt. I found the skirt, often yellow foam, only had one small strip of adhesive on it to stick to the walls and wasn’t a snug fit. I also had one without the skirt, blue, which had a full depth of adhesive on the rear that stuck really well to the walls and studs.

Definitely fill the cavity which will end up internally, which will help to prevent the chimney effect of heat loss

ASHP output will rise as the buffer heats, the system attempts to keep a constant DeltaT

Looking at your original photos, it’s definitely an improvement how it is now. You will find the white powder appearing (efflorescence) as they dry out, and as they’ve been wet for so long this is bound to happen, keep brushing it off with a stiff brush to keep it to a minimum. when I dug out to do external wall insulation below the DPC, I went all the way down to the foundation and it took around 6 weeks of fine weather for it to be completely dry, it will take some prolonged time especially at this time of year when it’s cold and damp most days

The combi is full of weak components and no cylinder, ergo something would just go pop if it ever super-heated the water. Loads of failsafe avenues there. If you heat a sealed cylinder, it becomes a bomb.

Thanks for pointing that out. There was no mention of it in the info I looked at, but I did have a concern at the time. Thinking about it, how is it different from the combi input heat, which would be far greater

You won't have a choice, if you put an immersion heater into a sealed system.

I dont like the added complication of the tundish and discharge pipe work in my situation Thanks for your input

If you have the space put a proper UVC in. The mini store is unlikely to perform much better than your combi except immediate draw of would be quicker.

Thanks for the reply "£1400 isn't modest in my book." *Agreed, it's modest compared to a heat pump and solar PV system though "Plus if used the way you are suggesting you would need a full safety group" Not familiar with this term, could you expand please "You may have a few things to resolve" Not sure I follow your logic in this paragraph The cylinder is heated from the heating side of the combi Via a 2 port valve controlled by a cylinder stat. A second 2 port valve valve would be required to allow heating via a room Stat. all this adds complication of course. The hot water side of the combi is not used. The DHW draw is via the the heat exchanger one side being mains fed the other to the taps, as there is very little stored water to be heated in the heat exchanger, way under 15L, so no tundish or discharge pipework required I do like your preheat cylinder idea, not sure it would help with the long draw off time though

It's all pricey. Block and beam is a good option and not esp costly. Where you say slab, it's probably a screed. Miles cheaper than a structural raft.

Excluding the fact op mentions block of flats do people here really get an SE to design how their windows will be supported in the opening?! For instance if building bog standard building regs you just overhang the cavity by minimum 30mm for part l regs. Nobody worries about whether the masonry will support the glazing. As @FuerteStu says the weight of brickwork in the same opening would be getting on for 250kg plus mortar just on the external skin.

Hi, Moved into a 1.5 story 1960s 'Chalet' style house a year ago. After living in the property for a bit we have got more of a feel of what works/ what doesn't and what we want from to achieve. The two main aims will be to alter the floorplan on the ground floor and to significantly improve energy efficiency (it's freezing). I have also become interested in retrofit. I am currently researching as much as I can whilst planning to meet with a few potential architects in the new year. Looking forward to learning from everyone on here! Dan

Just one, looks like she has a large nut cracker

Someone on here recently did a blog post with their place getting sprayed and back rolled i asked a question in the blog. I'd be paying someone I've tried it before with a cheap sprayer, had to pole sand the lot. As it happens a painter I know on site prefers to mist coat them before the skim has fully dried. Says they drink the paint otherwise too much topping up the roller. Can't really see a problem with this for a mist coat watered down anyway. He gets 150 a plot for mist coat whether it be 2 bed or 4 bed. He can finish them by 1pm and get back to the plot he's in. Has a neat corner roller for internals

Is it single storey? Even if its 2 storey if existing is 50mm cavity you might be overthinking this. It's not like the existing building is at passive levels of insulation. It's likely to not be the only cold bridge in the house whats the existing floor insulation? A 4" break should be fine

Hi Russell, I don't have the drawings for the DAN-wood house just yet; however I have the drawings for the previous timber framed house. That was as I described - made my eyes water!! 1.9m deep closest to hedge on strips 750 wide, graduating back to 1.1 deep on 500 wide, then the B&B with a huge void and finally a reinforced slab. That was for a passivhaus, but I'm not sure I should hope for it to be any different now, and I'm sure the D-W spec on site prep says something like 'do your SE-designed foundations, then cast a slab over the top to this specification' ... my computer's playing up just now, and won't let me access the files I wanted, to share more info.

As part of our proposed extension work, a current external cavity wall will become an internal wall. The current brick wall will have a 100mm slit to act as a thermal break, but I will still have a approx 4m length of cavity that is still "connected" to the outside. Do you see this causing any issues with heat loss? I can wet plaster both sides to help with airtightness - but I really don't want to add insulation to the walls on both sides (although I could fill with eps beads). The one idea I have in mind is to start the new block work from the old block work by having an approx. 250mm opening down the entire side of the wall and joining the two. This will result in a separation between the" internal" cavity and the external one. There are two challenges I see here: 1) with the 250mm opening, could it be done from bottom up without the need for any lintels. Google tells me this should be OK. Otherwise, we could do it top down. 2) the new block that will connect to the old would have to use whatever the current foundation depth is - at least for 150mm of the block. Would this be a problem?

SWMBO tried spray painting. Gave up due to the kit. Switched to what she knew and spent probably about 12 weeks on and off rollering and cutting in. About 270m2 of ceilings alone. But, it looks great. Plan is to live with white for several months, then apply colour if/when we know it's right