epsilonGreedy

If you took the time to review the thread timeline you would note: Someone asked me for a reference to clarify a below dpc stronger mortar mix. I provided a link to an NHBC table which illustrates the prescribed range of mortar mix/strengths in different use cases. Declan immediately countered saying he used 3:1 throughout and then questioned why would anyone try to save money using a weaker mix. I thought this an odd comment but then concluded his house was built using entirely of blocks in Northern Ireland hence his decision must reflect local building convention. In a direct quote of Declan's 3:1 recommendation, Jeremy seemed to reinforce this view by equating weaker mortar mixes with a questionable desire to save money. At this point I felt is necessary to point out that use of prescribed NHBC spec weaker mortar mixes where recommend, leads to improved structural integrity.

It is entirely relevant to illustrate why using a 3:1 cement mortar throughout house walls could lower structural integrity, which is a point you confirm later in your post. Some people reading the@JSHarrispost might conclude they should use 3:1 for the whole of their house which could lead to cracking as your say. All large structures are subject to stresses and movement. Their long term structural integrity is determined by how they flex in response to these stresses. By some measures cast iron is stronger than steel but a super tanker built from cast iron would break up in the first storm it encountered at sea. Houses and ships need to flex and using the right hardness/strength of mortar or grade of steel is part of the engineered solution. To impune that modern houses are suffering structural failure because the NHBC permits a variety of strengths of mortar is misleading. Indeed and what else should that be called other than the phrase I used above = "gross transgression of elementary building standards". My point is that modern houses have not been condemned because builders used NHBC specified softer mortar mixes.

If you mean it is "bonkers" to use any mortar less than 3:1 in strength then that would be bad advice. For hundreds of years mortar mixes have traditionally been far softer than current NHBC standards. Above dpc there are two competing considerations, on one hand a 3:1 mix is too brittle for a whole masonry wall and age old brickie lore is mortar should be matched to the strength of the brick or block. A wall built with a softer mortar can accommodate movement without fracturing. The 150 year old cottage next door to me has experienced obvious movement in its walls as the foundations have moved, had a modern house with brittle 3:1 mortar throughout its elevations been built on the same Victorian standard foundations it would have been condemned by now because a modern wall would have fractured under the movement stress. On the other hand a strong mortar is more weather resistant and so different regional regional practice evolves. The mortar failures in mass built houses that routinely hit the news are attributed to gross transgression of elementary building standards, nothing to do with dodgy modern standards that specify use-cases for softer mortar.

An easy to digest lookup table of recommended mortar mixes here: http://nhbccampaigns.co.uk/landingpages/techzone/previous_versions/2011/Part6/section1/appendix.htm#61C Thanks for asking because in responding I noticed that my future chimney stacks will require a below dpc strength mortar.

The mathematical cynic would observe that since your house is CO2 neutral and generates a profit as an energy producer then a percentage increase in your fuel consumption takes us into a new undiscovered financial dimension.

Good point, NHBC standards dictate stronger mortar below dpc which as you say is more effective at keeping water out.

All true but the absolute numbers in my post will help the OP comprehend that chasing ever better u-value figures is a game of diminishing returns which for a 2-story rectangular house 1800 sq ft in size, translates in trivial annual cashing savings.

Ah ha, that makes sense. The parting comment from a brickie on the subject of grey engineering bricks was "don't ask me to lay them in wet weather or the finish will be messy".

The House Builders Bible has tables showing the thermal performance and likely fuel costs for an average sized house built to 2013 and Passivhaus standards. The annual bills for hotwater and space heating are estimated at £800 and £224. The u-values for the 2013 house are assumed to be 0.18, 0.22 and 0.18 for roof, walls and floor. The 2013 model house is does not feature MVHR which accounts for 25% of the difference in thermal performance. Given that either of your u-value options is substantially better than the model 2013 house and you will have MVHR, then I suggest your option of 0.11 and 0.15 for different kits equates to less than £50 p/a in fuel bills for an average sized house.

The standard grey engineering brick in these parts at the BMs features three finger size holes right through the brick. Given the moisture resistant qualities of an engineering brick I am troubled by the thought these holes will be filled with moisture conducting mortar. I appreciate that the DPC is the ultimate moisture barrier but it feels wrong to undermine the essential quality of an engineering brick with a fast path for moisture.

I am a Spax fan, could this be a Beatles v. Rolling Stones type loyalty thing? Spax have a little extra bump on the bit head which helps keep the screw firmly attached to the bit. My Spax obsession led me to purchase an assorted set of 2,400 in a robust Spax branded carry case.

Eeek. Ceramic flooring will be the main floor cover downstairs.

I am coming under some pressure to screed my downstairs floor with flowscreed, as there would be an economy of scale thing (one pump for two houses). Reading up on Flowscreed I note a recommended max depth of 60mm. Why is this? Something to do with a mild exothermic cure perhaps? Background: This will be for a block and beam ground floor with UFH over 150mm of insulation.

TS? Trans Siberia vodka stores?

I know of a local case where just the scaffolding overrun charge equated to an extra £30 per m2, he got it revised down 50%.

Where do the duration-related extra costs creep in? I can think of material price inflation, extending site insurance, regular travel to the new build and temporary home rental costs though I know in your case this did not apply.

I can add: Pinging a neighbour's house wall to find the centre line of a hedge without walking on their property. Quick check of foundation dimensions when estimating hardcore and concrete orders. Checking tree distance from foundations. Covertly measuring the size of a nice example fireplace in a pub.

Did you struggle to get a passing SAP design with mains gas heating? I tend to agree with you about running costs however lowest running cost does not imply an optimum SAP score because CO2 generation is arithmetic poison in the SAP formula and scheduled to be a larger factor in the next standard as electricity will get a lower CO2 penalty due to the growing percentage of renewable generation.

Lasers were an unknown subject to me prior to my self build. I am happy with my DeWalt DW088 red line laser, it is effective outside within an hour of sunset given some cloud cover. My distance laser is a Leica Disto D2 which has been a major disappointment due to the poor ergonomics of the main measure button. This distance laser model has a bit more oomph than entry level models (though still a red laser) and it is effective at painting a dot outside in daylight conditions. I purchased red visor goggles made by Bosch which increase the ability pick out the dot at a distance they also make me look like an extra in a Star Trek movie. Still on my shopping list is a tripod with a fine tune height adjust mechanism, I currently use an old photo tripod which is fiddly.

Ok when armed with this additional knowledge how would you design an ASHP installation for an improved 4 bed 1800 sq ft 1970's house which looses say 10kw of heat when it is freezing outside?

I hear the same, it is odd that beyond the scope of this forum the prevailing folk law in the building industry is that ASHP = shivering disappointment. This seems to be because they are retrofitted into unsuitable properties on green initiatives and that general UK building construction standards have not caught up with the exacting standards of the Passiv House pioneers here.

That is odd because we have the same Council and when I volunteered to get the plot & static caravan registered for council tax they were happy to proceed. The initial address allocated came from the building control department which had an address error replicated on the tax bill, perhaps in your case you have not submitted diagrams to building control? In the first instance your property will have to be valued by another department before the bill arrives, Band A in our case. My main motivation for paying tax was for bin collection and on the first collection day I stood by the bin as the refuse team picked them up and explained the new address, "no worries mate, we just pick up any bins left out".

Do you need one and what for? Some people pursuing a "forever house" grand design need an architect to add value to a special or difficult plot. Others need an architect with specialist local knowledge to win over the planning office particularly when building in a conservation area. Later during a build an architect can offer an inspection/warranty service. At the other end of the scale with say a build budget of less than £200k you could avoid architect fees entirely by selecting a timber frame design off the peg.

About 50% of total build cost, maybe more if ground conditions are poor, service connection cost are high or you have a steep plot gradient.

Looks like quite a thick local slate or is that a trick of the light, how many mm thick? In my party of the world a Collyweston slate is common.