How accurate are QSs?

Mark,
 
I have a number of editions of your book and am now on the brink of my first self build. We have planning permission and detailed designs, and have had a couple of builders tender for the work, which was a condition from the bank in order that they would fund the project. However the costs are more expensive than I planned (surprise surprise I hear you say), and when I costed some of the major elements (ground works, external walls, roof) using your latest book, I came to half the price quoted by the builders. I have also got a few local sub contractors to quote and their numbers match mine not the builders
 
So I have employed a quantity surveyor to do it properly on my behalf, and am now the proud owner of 25 pages of costs for the project. Thankfully I am comfortable with this kind of numerical analysis, but I cam imagine at this stage most peoples eyes glaze over ! Unfortunately his numbers come in very similar to the builders (They would do wouldn't they I hear you say, they have both used QSs to cost the project and QSs will generally use the same process and hence come up with the same cost).
 
My analysis of some of the big numbers suggests that some of my QS's numbers are the same as the numbers from your book, but some are significantly more expensive (50% to 100%) more.
 
So my question is as a self builder what would your guidance be regarding the cost you can self build for Vs a cost given by a QS. Is there always fat in the QS figure to cover eventualities ? I guess I'm hoping for a shortcut rather than go through and cost the whole project using your book to come up with the relevant figure.
 
I want to self build but want to be ensure that there is a saving in there by doing this.

Regards,

John


John,

Good to hear from you. 

My feeling is that you are coming up against one of the age-old conundrums in building in that an awful lot of pricing is an art rather than a science. An expensive QS is probably about as accurate as you can get, but if you were to ask three other expensive QSs to undertake the same task you would get three different results.  And so it is with builders quotes. They will assess the size and difficulties of each task slightly differently and, crucially, they will assess the risk of these tasks being completed on time and on budget quite differently. The more off-beat the project, the more widely varied the quotations will be. My cost tables are really only there to provide the roughest of guidelines, not to construct quotations. 

One of the critical factors is risk - or more accurately the perception of risk. You have referred to it as fat which is how many people think of it. but its really a risk premium paid by you for them taking on the fixed price quotation. IE the risk of cost overrun is being transferred from you to them, and this is, if you like, insurance money for them taking on this risk. In theory, you can do away with this risk premium by becoming your own contractor/project manager, but you will only save money if everything (OK, most things) goes according to plan. If you prove to be a lousy or an unlucky manager, you may end up spending more money than the fattest of fat builder's quote.

I hope this helps. I realise this is very general advice, but as you note, it's a common problem which people undertaking selfbuilds face. We all want it to be costed out simply like a shopping list, but it almost invariably never works out like that.

Mark


Mark,
 
Thanks for your response. I think you maybe underestimating the value of your cost tables ! In your book you actually break each of the tasks down into material and labour which makes it easy to add up the totals. However the QS uses a fixed rate for tasks which includes labour, materials and equipment (i.e. £24 per sqm of blockwork - which I think is spot on for blockwork but some of the others seem very high). This makes it very hard to break down to see what is actually costed without working out the materials. Indeed the QS bemoaned the fact that in the old days he use to produce a bill of materials but now no one wants it. They just use the fixed rate to work out the costs, and then only ever plan one stage ahead. However he is very reluctant to produce a bill of materials for me.
 
I've just re-read your chapter on project management and it all rings true. I would just love to have the complete bill of materials so I could see once and for all how much the materials would cost Vs labour. If I use the QS's 40% is material and 60% is labour, then if I assume each subbie earns £200 per day (quite generous ?) then the labour cost is the equivalent of 10 people for a whole year !

Regards

John


John,

Thanks for the interesting feedback. I spend a ridiculous amount of time on these cost tables and rarely get any feedback on how people use them.

Mark

Are empty homes really a scandal?

This week we've been treated to a new housing campaign, launched on Channel 4. The problem — no, let's get this in perspective — the scandal of empty homes. George Clarke has been bestriding our screens examining what has been going down. From the bits I've seen, he has mostly been laying into the now discredited Pathfinder Policy of the last government, which sought to rip up old terraced streets up North and replace them with state-of-the-art, zero-carbon flats, or Yvettes, as they never quite came to be known.

You can trawl up and down Liverpool, Stoke-on-Trent or Sunderland and find really depressing looking wastelands of derelict and boarded-up housing estates. As Clarke kept pointing out, these could all be done up for.....well, it wasn't entirely clear how much. The key fact that he kept reiterating was that it was cheaper to do them up than it was to build new.

But the research from the Technology Strategy Board's Retrofit for the Future programme suggests otherwise. That is that if you are to create good homes fit for 2050 and our low carbon future, rebuilding may well be a more sensible and cheaper option.

Bringing these homes back to life would be expensive, however you go about it. And the fact is there may well be very little demand for these renovated or rebuilt homes in the private market. Liverpool, Stoke-on-Trent, Sunderland — none of them are exactly setting the jobs market alight at the moment. Set against the demand for affordable homes in these towns, things look very different, but that's not a market demand which would lead to people come in and spend money on these houses in return for sensible financial return.

So juxtaposing the number of empty homes with the affordable housing demand may look compelling, but it's voodoo economics. The fact is there isn't enough money for affordable homes whether it's building new ones or doing up empty ones.

Which isn't to say that there must be some spots where terraces of empty homes could be given over to enthusiastic community selfbuilders to make of them what they will. David Ireland makes this point in his open letter.

But the truth is that there will still be one hell of a lot of empty homes in places where no one is ever going to find a sensible use for them. It's very sad, but I'm not sure it really counts as a scandal.

Does Passiv mean Massive?

Ken Neal makes some interesting points on my last but one post.

• I do prefer to design passive houses rather than a PassivHaus, which are really active houses with all the kit and controls required. I do use and agree with all the standards, especially the airtightness but prefer to use passive stack ventilation. The additional heating load is about 1kW on a reasonably sized house which can be met, in rural areas where most of my designs are, by using a small wood stove.

Is he right? I don't think so. The Passivhaus only really requires one bit of kit - the mechanical ventilation system (MVHR). Sure, this kit requires controls, but they are not overly complex. Think Off — On — Boost. That's pretty much it, although there may be some element of timing involved as well. But nothing more complicated than a conventional heating system. And if you do choose to use natural ventilation instead of MVHR, you have the problem of not being able to circulate the warm air around the house, so that your wood stove wouldn't be heating the other rooms in the house. Natural ventilation requires significant input on the air intake side and that can realistically only mean trickle vents, which immediately blows a hole in your airtightness strategy. You can see why Passivhaus and natural ventilation don't really go hand in hand.

• I also prefer thermally massive houses, where you can get several days carry over of heat, to typical PassivHaus lightweight structures.

Passivhaus is agnostic on this point. There is no presumption in favour of lightweight or heavyweight structures. You can have whatever you want, so long as the thermal sums add up.

• I like a house which just sits there and does its thing on its own with very little control or active input.

Well, that is pretty much what a Passivhaus is aiming to do. But to get there, you need MVHR. Natural ventilation just doesn't cut it.


• Regarding embodied energy in materials, this only becomes significant if you are designing for a short life, say sixty years. In our energy constrained future we won't be able to build quantities of new houses, or alter significantly existing ones, because the energy to do so will be in short supply or too expensive or both. If you look at the age of some of our present housing there is no reason to suppose that a well built passive house won't last for three or four hundred years. So over that lifespan embodies energy is a very small proportion of the energy used in a building.

Basically, I agree with Ken on this point. But it does rather contradict his first point about the additional 1kW heating load placed upon a house without MVHR. Because that 1kW load will mount up over the lifetime of a house. After about twenty years, it will equate to the embodied energy of a lightweight house. After 40 or 50 years it will equal that of a heavy, masonry house. Those kilowatts, they all add up.

Mike Jones also makes some interesting comments on the same post.

• I plan to self-build to Passivhaus standard but I'd like a simple efficient MHRV system that I can service myself so I do not have expensive maintenance costs. Are the Passivhaus recommended MHRV systems easy to maintain by the householder or is maintenance a factor to be added to the building running costs? Anyone know?

I don't know enough about MVHR to answer that for sure. One of the issues to be resolved is that whilst there are dozens of MVHR systems on the market, very few are "Passivhaus certified." And whether these need professional servicing, I have no idea.

Half FIT

One morning two weeks ago, I was awoken by some banging coming from a neighbour's roof. Draw back curtains and, lo and behold, across the street, some guys are up on the roof, seating some PV panels. Now this is a street running North-South, which means the panels are facing due east, so the amount of power they will create will be well down on their designed output.

To me, this was a sure fire sign that the Feed-in-Tariffs (FITS) had gone too far. Harvesting sunlight to make electricity in this manner is never really going to make much sense in a northerly latitude like ours, and doing it inefficiently like this really offends me. No way would anyone ever conceive of erecting east-facing PV if it wasn't for the promise of a big fat subsidy cheque. I've never liked these subsidies (having bleated about them on this blog often enough) and I don't have a huge amount of sympathy for these businesses which have apparently been "caught out" by this week's announcement that the subsidy is to be approximately halved forthwith (actually from December 12th).

Building a business plan on the whims of government renewable subsidies has never been a clever idea, especially in the UK which has a lamentable history in this area. We had Clear Skies, launched in 2003: they cocked that up. We had the Low Carbon Buildings Programme, launched in 2006: they cocked that up. Now the FITs, launched way back in April 2010, show every sign of being cocked-up too. Roll on the Renewable Heat Incentive!

On 2011 UK Passivhaus Conference

Monday and Tuesday this week saw me at the 2nd UK Passivhaus Conference at the Barbican Centre in London.

There were around 250 attendees consisting of a fair smattering of old AECB-heads, a fair few BRE types, a sprinkling of academics and a good gaggle of "people who had come to learn." Consequently, the conversations ranged from the basic "This is what a Passivhaus is" through to the arcana of extreme building physics. The Passivhaus Trust itself would seem to be in rude health, energised by the fusing of the AECB's enthusiasm with the BRE's clout and professionalism.

Not everyone in the sustainable building arena buys into Passivhaus as a concept. Some decry its enforcement of MVHR (mechanical ventilation), others are suspicious of its cult-like qualities — it's very much the brain child of Wolfgang Feist and he gets to decide who and what gets certified, as well as remaining the owner of the PassivHaus Institute. But the beauty of PassivHaus is that it's a relatively simple standard, it appears to be based on solid building science, it's been shown to deliver what it says on the tin, and it's an internationally recognised standard, thanks mostly to the tireless promotional work of Feist himself. And in the UK in particular, Passivhaus still represents a giant leap forward on current building standards, even low energy ones, so it's not hard to see why the green building movement (OK some of it!) is so keen to promote it.

Day Two was for me the more interesting. It delved into a variety of technical topics and it would have been good to be able to sit in on them all, but the nature of the breakout sessions was that you had to choose one from three. Mark Siddall was particularly impressive on the subject of thermal by-passes and wind washing, a topic that lies beyond the confines of Passivhaus, but goes a long way towards explaining why low U value walls and roofs don't perform as designed. I also sat in on a good session given by Paul Tuohy (Strathclyde Uni) and Prof Chis Tweed (Cardiff) about the problems of post-occupancy monitoring. Everybody and their aunt calls for more of it, but the process is fraught with difficulties and the results are sometimes meaningless because there are so many incidental factors at work. Co-heating, in particular, was singled out as being hugely unreliable which is interesting because the practice involves keeping the temperature in a building constant over a long period and measuring the resultant heat loss, which reminds me of the tests run all those years ago by Actis to show that their multifoil was the equal of 250mm mineral wool.

Another observation was the ever growing interest in natural building materials and breathable fabrics. This is another area on which Passivhaus is silent: it emphasises airtightness above almost everything else, but has nothing to say on vapour permeability or embodied energy. Should these be included? Is there good practice to be passed on here or is it just getting too complicated?

And, more than once, the subject of quality control came up. Much of the success of Passivhaus is down to ensuring that the building is designed right and built right and the official or certified Passivhauses have to go through an expensive (like £2,000) and fairly rigorous auditing process. The materials need to be checked off, invoices examined, photographs taken. All very anal and tedious but critical in delivering quality. Some people are of the opinion that the certification process lies at the very heart of Passivhaus and is the main reason for its monitored success, but others feel that it's much too expensive and the certification cost needs to be reduced. It's a political point as well because Feist's PassivHaus Institute is resolute in insisting that they remain the police force here and they fear that any move away from this will inevitably lower standards. The UK Passivhaus Trust is firmly in Feist's camp but other countries (notably the USA) are taking a more relaxed view, claiming that the standards should be open and usable by all.

In one sense they already are. Anybody can look up what the Passivhaus standards are, anyone can purchase the design package (the Passivhaus Planning Package), anyone can claim to build to these standards. But where is the quality control? Without some form of rigorous certification process, how can you really know you have built a genuine Passivhaus and not a pale imitation that doesn't deliver energy savings as designed? It's a big issue, arguably the biggest one surrounding the Passivhaus movement. And it's interesting to note that of the 30,000 Passivhaus buildings constructed to date around the world, only about 10% have been through the official certification process.

Which brings me onto my final point, if it's the certification process which is the BIG THING, then maybe there's nothing much wrong with our building regs as they now stand, if only we built them properly.

Brownfields, no gardens

Last Wednesday evening (actually Sep 21, the day before I locked horns with the National Trust), I attended a talk put on by Cambridge Architectural Research and presented by David Birkbeck, who runs Design for Homes, and, incidentally, someone I have known for many years, having once written for Building Homes which David once edited. David is also a selfbuilder and I have written about his exploits here and here.

But he wasn't in Cambridge to talk about selfbuild, he was instead chewing over the Housing Design Awards and how the styles and fashions have changed over the years. He covered the last 15 years, the time that marked the end of the cul-de-sac style developments of the 80s and 90s, and the move into brownfields, Georgian densities, and flats. And Poundbury-style site layouts.

He was interesting on Poundbury, and quite critical of the tortuous road layouts it uses (all curvy and wiggly and seemingly chaotic). Much better to go the whole hog and build squares and streets, like the Georgians, and indeed he showed that the current crop of award winning schemes all tend to do this. (I'd pepper you with examples but, of course, I wasn't taking notes and I have trouble remembering stuff a week ago. In any event, you can access them at the Housing Awards Website.)

But towards the end of the presentation, the subject of gardens came up. Or rather, the lack of them. The current trend is to move away from simple balconies towards roof terraces which aren't overlooked, so you get a bit of decking and a planting bed or two, next to which you can place your sunlounger and pretend you are somewhere else. Often, these areas are situated at first or second floor level and have someone else's home underneath, so they are in fact variations on the intensive green roof. David mentioned that there are already a few claims coming in for water penetration through these green roofs into the homes below and he suspected that we would see more of this over the coming years. It's not altogether easy or practical to build a roof garden, but that's one of the consequences of our predilection towards building at Georgian densities (although I don't recall the Georgians' going for roof gardens!)

I like a bit of irony, so I couldn't help thinking that the current National Trust anti-NPPF campaign, if successful, will continue this urban cramming trend we have embarked upon (otherwise known as the brownfield first policy). The flipside of "Protect Our Countryside" is "Ban the Garden."