Dreadnaught

I am choosing my timber frame company for my modern bungalow in Cambridge. One respected company has offered a floor made of eco-joists rather than the usual reinforced concrete passive slab I had assumed. I am worried about the floor sounding hollow and making the whole dwelling feel flimsy and insubstantial: Anybody have experience of a ground floor made with joists? Could I perhaps screed such a floor to give it a more solid feeling (and create a space for UFH)? I wonder if such a construction would be cheaper than a passive slab. Any guesses? Any other pros or cons to using joists for ground floor? Overall what do people think, joists or slab? (My foundation system is screw piles. The build will be near passive.) (By the way, with joists I know I would lose the ability to use a slab as a thermal store).

A very clear presentation, @Visti! Very helpful. Is your logic correct: does a board of a given density provide the same acoustic attenuation as double the amount of board of half the density? In other words, is kg/m² linearly proportional to acoustic attenuation, and across all wavelengths? As your research continues, I would be interested to know your view on using resilience bars? If you choose to use standard board, will you therefore be wet skimming with plaster too?

Out of interest where did you choose to install resilient bar on your ground floor? Everywhere or selectively?

Surely that's the shortest conceivable complete sentence. It is almost perfect, bettered only if it had punctuation. No?

Habito strikes me as a half-way house towards Fermacell with regard to fixings. But as I understand it from reading the official literature with Fermacell it is possible to use the score-and-break technique. On a tangent, I wonder how the specific heat capacity of OSB or plywood compares with plasterboard or Fermacell. I recall @Jeremy Harris mentioning the benefit of the combined influence of all the plasterboard in a dwelling on the thermal time constant of the internal climate.

Thanks @Roundtuit. Yes please. PM on its way.

Thanks @Oz07 Not really sure, to be honest. Just feels right not to while I am choosing. Public forum and all that. Oh that's not the kit one. That's the local company proposing using their classroom-suited solution: they do erect. Reason for possibly substituting blown cellulose for rockwool is only because it has a better decrement delay. I think they have similar λ values (W/m.K) so there probably isn't much difference there.

Sure @oldkettle. PM coming right up.

Oh, I missed the tiny minus symbol too and thought it was an error.

Thanks again, @Sensus. Appreciated. Just checked my red line: they are outside of it. Phew!

Thanks @Sensus. Very interesting. Should I just leave the condition there and challenge it only if it was ever used against me regarding a tree not on my land? Or would it be better to have the condition removed, because there are actually no trees on my land to which it could apply and it is therefore an irrelevant condition? (I got my planning approval just three days ago by the way).

I just read @Sensus mention in another thread that: "the rules are that [planners] should not impose Planning Conditions unless a number of tests can be met - one of which is that the Condition must be enforceable, which it is not" (my emphasis). It was not in that case because it related to influence over an object (a wall in that case) on land which the subject did not own or control. In my case, I have the planning requirement shown below. However, none of the trees near my plot are actually on the land I own, they are all either in neighbours' gardens or in the access road outside my plot. (At least the tree's trunks above ground are not on my plot. Their roots extend under my plot of course.) I wonder, does this requirement therefore not apply to those trees in my case? Can it only relate to trees that are on land I control?

Good idea. I will add it to my list of questions.

Yes, quite right, we will be removing two small trees that are within the footprint of the dwelling. Just to be clear, there are no other trees on my plot. The big chestnut tree is just across the fence.

I appreciate your frank comment but overall I am confident we'll find a way to work within the root-protection area. I think I have chosen a good practical arborist. And we have already had one site meeting with the LPA tree officer (with one more to go). Lets see if it will drive me to distraction! I am no expert of course but I believe that the RPA has indeed been defined in the AIA* according to the standard that cite. The AIA was a key document in obtaining the planing approval. And now that I have panning approval, the next step is to write the full AMA* and TPP* and have them agreed with the LPA tree officer. Fully agree. Hopeful of retaining use for storage of a substantial area within the RPA. Sounds about right for this tree. It is a big fat old chestnut. * AIA = Arboricultural impact assessment. AMA = Arboricultural Method statement. TPP = Tree Protection Plan.

Obliquely related to this, I do have a planning restriction to replace a tree as follows… You describe my chestnut tree precisely

As I mentioned in my last post, as one of my very first actions I feel that I need to talk to my arboriculturalist. I think that many subsequent decisions depend on his answers. My small plot (20m x 20m) has a chesntnut tree on its border and its roots are to be preserved. Those roots spread under about half my plot. And it is the half between my access gate and where the dwelling will be so exactly in the wrong place. Everything will travel across the roots. And the root zone is almost also the only location on the plot where I can stoer things during the build (other than inside the dwelling of course). I have a whole host of questions for my tree guy, I have a couple of possible routes across the plot for the drains and services. Which is the better one for the trees? When it comes to the build, how can I arrange storage on site without damaging any tree roots? For example, the plot has an existing area of old block driveway right in front of the gate and over the roots. Should I keep it and use it for storage during the build? Or lift it out and put some other root-protection surface down instead? Should I take any root-friendly precautions when I clear the plot? I am having screw-pile foundations but how deep can I scrape and level the plot, particularly as I have about 40 cm of height difference across the plot (lumps and bumps, not a consistent gradient). When to clear the vegetation (otherwise known as “the jungle” from the plot)? Any precautions to take? How to stop weeds regrowing. There are quite few derelict low-level brick and concrete structures on the plot, mainly consisting of the foundations for long-since-gone greenhouse? Should I just rip everything out, or should be concerned about tree roots in doing so? In particular there is an old concrete water tank sunk deep into the ground (like a water butt from the ‘50s, about 1 meter square, open to the sky). It has what seems to be a land drain running into it. What to do with that?

My first jobs after my planning approval are to: (i) choose a timber-frame supplier; and (ii) arrange a conversation with my arboriculturalist. This post is about the (i). The next post will be about (ii). Timber-frame suppliers: I am in touch with the usual names known to this forum. Not sure if I should be naming names here. Six in total. Two companies supply panellised frames with a range of insulation levels, including open panel and double stud. Two companies supply I-beam-based frames, one of which is a company local to my plot in Cambridge, just 30-min away. One company provides a passive-house certified I-beam frame but as a pre-cut kit, complete with all tapes, etc. Frame erection would be by my own team. Quotes from them all are due by next Friday. Some random thoughts on my choice … The local company proposing an I-beam solution is interesting. Its a solution they use for school classrooms: I-Beam walls and roof filled with rock wool, although I see no reason in principle why the rock wool could not be replaced with blown cellulose. Airtightness using SIGA tapes & membranes. My dwelling is very simple in form (a simple L-shapted bungalow with a flat roof about, 125 m²) so when the rep from the this company saw that he immediately suggested this solution. Looking forward to that quote. My plot has problematic access: small plot, about 20m x 20m, a narrow 45m access road, mature tree overhanging the only gate, no space for a big crane. So a non-panellised I-beam solution has its attractions, although I suspect I am over doing it as one of the panel-based company seemed to think they could manhandle the panels on to site pretty easily, especially for such a relatively small build. The passive-house pre-cut kit supplier is also interesting. They provide everything from frame design to foundation design to PHPP and the kit includes Austrian passive-certified windows and MVHR system too, as well as the I-beams, all membranes and tapes, and all to a single firm price. They also include training sessions for your contractors. If I went down the route of a stick-build, albeit pre-cut I-beams, I have met a carpenter who is doing exactly such a build at present and using the pre-cut kit provider above. He has expressed an interest about possibly coming onboard in the spring and thinks he could erect the frame in 3x weeks. That sounds quite interesting as an option. As you can see I am mid-decision and still thinking through the pros and cons for my particular circumstances.

Next we'll see a roll of airtightness tape in his mouth …

I have just got my planning approval 2-days ago. My 26 weeks date was back in about July (!) but they never asked for an extension. I think it was an oversight on their part because of a change in planning officer. Yesterday, a day after the planning meeting, I received an email from them inviting me to retrospectively approve a planning extension (!) which I politely declined. I am going to ask for a refund as soon as I get the signed planning letter through. A few weeks ago I did mention the possibility of a refund to my planning officer and he said they might refuse because I supplied some key documents within 26 weeks of this final decision. I don't think that is in accordance with the Planning Guarantee and the wording of the regulations, which requires an extension to be agreed in writing, so let's see what happens.

Thanks @Mr Punter and all the regulars here. Mine will certainly be a BuildHub build, all the way through.

Thanks @Mr Punter. Good advice, appreciated. I have to admit to being wary, hence the wish to de-skill as much as possible, do as much myself as I can, and be close to the detail of everything. This is not related contractors as such but Its interesting to note that at even at this early stage, without having broken ground, I have already experienced two occasions on which experts have blatantly tried to take advantage of what they assumed was my lack of knowledge to over charge (and who knows how many I didn't spot). As the spend now ramps up, I suspect I am going to doubly vigilant (perhaps to a fault).

Thanks @PeterStarck. I'm hoping for foundations and frame in the spring next year. Weathertight as soon as possible thereafter. And then probably at least a year's worth of first fix, second fix, and finishes. So completion in summer 2021 would be a pleasant surprise but won't be rushing things and happy to go slower. My getting-my-hands-dirty approach will be nothing compared to what you achieved! I will be using the trades regularly but doing the bits I can. But I am also trying to design the build to be as simple and easy as possible. For example, I am keen to use no-wet-plaster approach if I can. And I am choosing a brick slips system for cladding that does not require a skilled installer, let alone a brick layer.

Haha, what an idea! What public accountability! Building-the-Dream and Charlie-Luxton style. My budget is more of a cost tracker. Its a complex spreadsheet where each figure is matched by a confidence rating. As I learn more about a given item, drywalling for example, I increase the its confidence rating. That then can be summed to a bottom-up total figure for the cost of the build. Currently about half the items in that sheet are nothing more than guesses. However, another way to answer your question is: £360,000. That's a top-down figure. That's the target figure to ensure the land + plot ≤ to the sale price. So that is about £2,400 per m² for the build including everything except the plot cost. It includes, for example, the conveyancing costs, planning permission costs, and the proverbial kitchen sink. My bottom-up figure and my top-down figure have a current gap of £9k, which is in effect the current contingency amount but that has been shrinking as I learn more. At present I intend to be hands on a do as much as I can DIY. Whether that intention will survive even first contact with reality remains to be seen. On the time/cost/quality triad I am firmly aiming for cost and then a sensible compromise between quality and time.

Oh yes, good idea but the plot looks rather like a jungle at the moment. I live about 2½ hours away from it so I haven't been a dutiful gardener.