epsilonGreedy

Good to hear Option-3 is viable. I was hoping that spray insulation would: Be cheaper. Create a better air seal. With the machine available I could zap some other voids in particular the blockwork face between the ceiling and first floor boarding. Some YouTube videos show that in the US they fill all nooks and crannies with the spray nozzle. Mean no need to shape PIR sheets around service conduits, cables or pipes. The downside of foam could be: Cutting away excess. Noxious gases for days or weeks? Possible chemical argument between HEP or electric cable plastic. The benefit of PIR panels I can see are: It suits a progressive approach to finishing the house rather than a final big bang spray day. It is reversible if I need to route something extra down a wall. When you say the "batten it to trap it" is this a temporary measure prior to fixing plasterboard?

I wonder if I am creating a problem that does not exist about reveals. The concern I mentioned in my OP related to attaching the frame (wooden sash) to the nothingness of a large cavity. To overcome the block sealing issues I am already mentally prepped for a couple of days of sloppy mix parge coating. The other problem is that I imagine a full wet plaster job would render the house uninhabitable for a couple of months as it sheds all that water. I reckon the walls will be ready for finishing this time next year.

You have an excellent end result there and it would be compatible with the heritage rural look I am after. 200mm hmm, I would need to recompute internal room dimensions and judge the reaction on swmbo's face.

I confused a petrol forecourt nighttime cashier the other day asking for a Marathon bar at 1am.

I am close the point where the architectural technician assigned to creating my building control diagrams will ask me to confirm the thermal layer build up for my brick & block walls. My options based on my own research seem to be: 150mm cavity plus basic dot & dab dry lining or classic wet plaster on blocks. 100mm cavity with exotic thermally performant blocks for the inner wall plus dry lining. 100mm cavity plus commodity blocks plus 25mm insulation between battens on the inner block finished off by regular screwed on plaster board. My location means I can have a fully filled cavity. Option-1 will create a problem with a full brick reveal sash window frame due to the extra cavity width and I will loose an inch or two in many rooms. The house is L-shaped hence the sq footage loss is more painful. Option-2. I have yet to get my head around the range of blocks available but the handling/fixing/cost characteristics seem to worsen inversely to thermal performance. Option-3 is my favoured route because I feel it will offer more flexibility for a slow progressive diy 1st and 2nd fix where I will be camping out in the part finished house. I also like the idea of been able to work my way towards fully functional electrics/plumbing/heating and living with the guts exposed for 3 months. Then if nothing leaks and all electrics seem properly positioned I can then hire a machine and squirt 25mm of insulation foam between the battens, trim it back and attach the plasterboard. I also think the 25mm of inner foam will be more effective than its R value contribution indicates. @JSHarris prompted this thought a few months ago when he suggested that an inner block wall can become chilled through thermal bridging and dry lining convection. Has anyone done a selfbuild following my Option-3 and concluded it was a good solution?

Thanks all. At this point 140mm wide blocks as suggested by @Brickie seem like the simplest way to beef up a supporting wall a tad.

The main load would be first floor joists so I suppose upper floor stud wall weight is transferred down through these. Do significant roof loads also get transferred down via trusses and stud walls?

The external brick/block cavity wall is 10.5m long in my case and this partition wall being discussed is at right angles at the 5m point half way along. I will be removing an internal chimney breast at the 3m point but in its place will be a kitchen range alcove which could be structurally enhanced with small side walls meeting your 450mm criteria. Oh I see, I was going to ask in another thread if posi joists embedded within a block wall contribute to lateral masonry "panel" stabilization. I think you are saying that mortar bedding of such joists is not that useful but the straps create a structural connection. If so I might be overthinking this as usual and so can downgrade my oak beam to a decorative function and make sure it is strong enough to support just its own weight across the 2m span. The alternative building controller has previously approved 750mm return walls because she says this allows a nice big aperture between kitchen and snug plus her 600m deep larder cupboard will tuck in behind one of these.

Ok. I also imagine mortar adhesion is a big factor for the upper block courses. Here I am thinking about cyclic flexing of first floor joists and associated lateral twisting of the top of a block wall.

Right, so rather than fussing around with the block equivalent of English garden wall bond, just do stretcher bond with the blocks on their side. Like it. Have just been looking at various block sizes for this, I must do some maths to see which size is simpler to tie into a regular 100mm external block wall.

This is what a rational pro builder would do. The irrational self builder in me wants to be able to tap a real solid oak beam and know it is making a structural contribution to the house. I will also be able to spin a yarn that my reclaimed oak beam is rumored to have once supported the upper deck of one of Nelson's ships of the line.

I am struggling with the concept that a single skin 100mm thick block wall that is 24 times as high as it is thick, can be called a supporting wall. This is just an intuitive feeling not based on any evidence. My house will have one major internal supporting wall about 5.4 meters long, this will have a wooden stairs attached and a 5m run of posi joist ends sitting on it. Upstairs loads will be minor, just stud walls and no roof loads transmitted though. If space and money allows, is a double thickness 210mm block wall far more sturdy? My budget can accommodate this cost because the switch to an open plan sitting room with stairway means that a buddy wall to the remaining supporting wall has been removed from the original design.

In my house the RSJ would not be supporting anything above and the first floor joists will be orientated the same way hence they can do all the supporting of the first floor and stud work above. So any remaining function of the RSJ would be lateral bracing of large panels of masonry wall. The original architect showed a dividing wall between kitchen and snug with just a smallish pair of glazed french doors. This meant the masonry portion of the dividing wall was about 1m each side of the doors. I assume that with an enlarged opening the vestigial masonry wall each side no longer provides enough lateral support to adjoining major walls hence the RSJ ties the vestigial walls into a continuous structure. I need to have a chat with my neighbour to ask why the RSJ appeared in his design solution, maybe he needs to support something fancy like a large thermal store point load above. The reason for this question is that I was looking to verify the oak beam would be a reasonable request to load onto the architectural technologist who will be producing the BC diagrams.

This is what my self build neigbour has done i.e. proper water supply trenching to the front of the house, then a temp T connection and a long run of garden hose to the caravan.

I would like to have an exposed internal oak ceiling beam between kitchen and snug where currently in a similar position my neighbour's selfbuild house has an RSJ bridging across a 3m span, my span will be 2m. His RSJ sits on two substantial internal wall block wall supports built out of adjoining block walls (about 700mm x 250mm thick x 2.4m high ). The oak beam would be at first floor level and appear to be a ceiling joist protruding below the ceiling plasterboard. I think the purpose of the RSJ is to provide a horizontal tie between an internal 6m block wall supporting a stairs and an external wall 8m long masonry cavity wall that is otherwise only braced by posijoists. Can a 2m long lump of oak beam provide the same lateral tie structural function as an RSJ?

Yes no problem. The cooperative pro builder of that plot also suggested I get my levels from his now that he has done the leg work of finding a substantial local reference for his setting out. Safety in numbers I suppose.

I used metal tent pegs for my trials runs as these were easy to remove and so no opportunity for an ambulance chasing fraudster to claim wooden pages were a source of hazard and injury. I also found it was better to focus effort on marking out a large accurate rectangle that enveloped the whole house and then mark out more fiddly footing details with reference to this master outer box. The alternative is marking out one box relative to an adjoining box but I found this led to errors.

I am at a similar stage and considering diy setting out to save £500. My house position is also vague with nothing substantial available for precise positioning of the footings. I have two hedges, a lane, another ancient property about 15 meters away and one new house 30 meters away in-build. The local planning officer told me they don't resort to enforcement when the position is less than 0.5m out. My house also has an interesting rotation 10 degrees different to the building-line alignment of nearby properties, so I plan to reference a solar azimuth table and align the front elevation to a shadow at the right time of the day. I have done multiple trial set outs of the foundation plan by resorting to school boy trigonometry, the bit that worries me is "levels". I don't get all the mystique about levels but have 3 weeks to get my head around the subject. Everyone in the building trade assumes I will be paying an expert to obtain laser calibrated "levels", this feels like overkill considering the max fall across my footings is 250mm. Easy visual trigonometry can be done at this web site, it is preferable to scaling up from 3,4,5 triangles: https://www.visualtrig.com p.s. Do all you trigonometry diagonal length calculations back home on a desk, it is too much bother to fiddle with a trig web site at the plot on a sunny day.

When I went solo offshore sailing I still put my lifejacket on and then wondered why as there would be no one left onboard to turn around should I fall overboard. In the end I concluded the lifejacket was a security dummy.

And for me its the location too. The first thing I look for in any property is how it relates to the local topology, next comes community. My plot sits within some interesting folds in the Lincolnshire Wolds which remind me of the ups and downs in south Devon. I recall standing behind Swmbo on our first visit to the plot, pointing to a hill 1/2 a mile away and saying if we are up early on a spring morning and look out of the bedroom window the sun will be highlighting the pastures at the top. On a subsequent walk around the village we encountered happy folk leaving the weekly woodcarving class and further up the lane an old gent was selling cottage garden plants from his front garden in aid of the village hall. Grand designers will find little of interest in my future modest house however for the past 15 years I have often described my dream house as a Georgian rectory sitting on some rural hills about 15 miles from Exeter. My mini faux Georgian rectory does not fall too far short of that dream house.

In defense of the building trade, might those crumble blocks just be positioned markers to help the beam layers avoid obstructing the timber frame supports.

I followed @recoveringacademic 's link and did not encounter a pay-wall. Are you referring to the cost of a printed copy?

Best assume no PV. The architect showed an airing cupboard upstairs, I will retain that space for a later DHW thermal store upgrade in say 10 years time and ensure it would not be too problematic to connect up with spare pipes and high current wires. Brick & block construction just meeting current thermal regs but hope to exceed air permeability by a large margin. L-shaped 2-story house 10m x 6m + smaller 2 story block of 4.5m x 4m. All dimensions external. There is in fact an even smaller 3m x 4m single story utility room/toilet block attached to the far end of the 4.5m x 4m block, however given the relatively large perimeter to floor area of that section of the house I feel that a couple of small rads will do there. Current plan is that the upstairs will be heated by 1 small rad in both bathrooms plus 1 mid sized rad in the master bedroom. No science behind that thinking just a hunch.

No. It is more like saying there is a time and place for hot air ballooning e.g. best done 2 hours before sunset and try not to land on the main runway at Heathrow.

I have been watching a lot of Skill Builder material recently and feel they pitch at my level. In the bathroom video I "discovered" that a wall-hung bathroom was assembled from the outer wall inwards whereas previously I imagined the reverse where the finishing step was to plasterboard the far side of the wide partition wall. There were little info gems for me such as the importance of rubber feet on the wallhung toilet frame to reduce noise transmission. One convincing message from the video is that a diyer like me will have fewer head-scratching delays or trips to a BM for the reverse angled thing-a-ma-jig because of the benefit of integration. If true this would justify a price premium for someone in my situation though deep down I suspect this is just a staged demo illusion.