danielclarke

Exterior wall for steel framed house

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Hi Everybody,

 

I am new here. Thanks for reading.

 

I am in the process of trying to plan a quick to build and affordable bungalow of approx. 120sq mtr for a budget of £60k. I need to avoid complicated machinery and build with minimal specialist trades onsite. I also need the property to be watertight as quickly as possible. 

 

The house structure will be supported by a steel portal frame. The challenge I have is that I’d prefer not to use brick or block as ultimately it takes too long and you still need to account for insulation, etc. – it’s just too labour intensive and time consuming. To add to the issue, I am not at all keen on wood cladding or anything like that. What I’d like is a nice smooth modern exterior, so I was thinking pre-fab walls or something easy and quick to put up. Whatever it is, it does not need to be load bearing because of the steel frame, but it does need to be super energy efficient.

 

Any ideas or recommendations?

 

Appreciate it!

 

Daniel

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Hi and welcome to the forum.

 

At a target price of £500 per square metre that is going to be challenging to say the least. I wish you well with that and expect to achieve that you will have to do just about everything yourself.

 

There are various man made cladding materials and don't rule out a render finish, but ultimately the decision is more likely to be what the planners will accept not just what you would like and what is cheap.  You could choose a super thick timber frame to fill in the walls which is easily DIYable then it's just the cladding to choose. If you like the idea of render then you could clad in a wood fibre board that gives more insulation and takes a thin coat render directly as I am building with.  I did have to pay someone to do the rendering as that is not in my skill set (I would have made a lousy job of it)

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Welcome.

 

Building for £500/m² is a very, very tall order, and frankly I doubt that it's possible, even with a great deal of work done by yourself, with almost no contractors involved.  The cheapest self-builds are probably around £800 to £1000/m² and can only be built at that price because of a lot of hard work by the self-builders.

 

I'd guess that a lot of self-builds tend to come in at between £1200 to £1500/m², at least those that don't have a particularly high specification.  Up the specification and it gets easy to exceed £2000/m².

 

Also, a lot of the cost depends on where you live and what the local labour rate is, and also whether some materials are cheaper or more expensive locally.  For example, steel fabrication costs have a fair proportion of transport cost in the total, as well as having plant hire costs for erection, and in some areas that can increase the cost a lot.

 

To give an idea of cost, our build is 130m², and I did the design (no architect), the planning and buildings regs submissions, project managed the ground works, did all the plumbing, heating and ventilation system installation myself, did almost all the internal joinery myself, fitted the kitchen, bathrooms, WC etc myself and a fair bit of the electrical work as the qualified electricians "assistant".  The cost came in at around £1380/m², or around £180k.  I could have reduced this a fair bit by having lower spec joinery and cheaper kitchen and bathroom stuff, and may well have been able to manage to get the cost down to about £1250/m².  That's still a long, long way from your £500/m², though.  Even our basic watertight shell and foundation came in at around £410/m², without the roofing, windows, doors etc, just a membrane clad shell.  It did go up in four and half days, though.

Edited by JSHarris

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Hi Guys,

 

I want to keep it under £60k if at all possible, and I do think it is possible to get close, though I do admit to still being in the middle of my research and planning... I will be doing most of the work myself, with the help of family - that covers all plumbing, electrics, etc.

 

The spec will be smart basic, open plan, minimalist. If you're sensible, I do think you can get a great looking house on a budget  by avoiding labour costs as much as possible and also by avoiding bespoke goods, etc.

 

The steel frames I am hoping to use are the same frames used for agricultural and storage units worldwide, so you get an abundance of space at a minimum of cost. These can be purchased cheaply, they can also be supplied locally and erect quickly. Using this system avoids expensive foundation costs too.

 

Planning is obviously going to be the biggest challenge with this, but it has been achieved already in Wales and I want to give it a shot here. Property in SE England is just ridiculously priced, so my hope is to give people an affordable self-build option. I know it isn't going to be easy, but I am an optimist!

 

Really appreciate the feedback guys.

 

Regards,

Daniel

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I wish you the greatest luck, but think you've got a great deal of work ahead to get down to £500/m².  If you're in SE England then your task will be a great deal harder, just because labour and other costs will be higher than somewhere like Wales.

 

I think the cheapest build here may well be @Declan52's build, where he did a great deal of the work himself.  He's also in a pretty cheap area, compared to SE England, so would guess his costs may well have been around 20% to 30% lower because of this.  I'm not sure what his build came in at, but have a feeling it was around £800/m² or so, which is extremely low, probably the lowest I know of.

 

Your going to need foundations, with low thermal bridging if you want a low energy home, and just the cost of the cheapest type of insulated floor and foundation is going to eat up around 25% of your budget, even with you doing all the labour, and getting materials at a keen price.  Designing a thermal-bridge free, internal steel portal frame structure is certainly possible, but you'll need to do a lot of the design and thermal modelling work yourself to keep costs down.  The devil will be in the detail, like how you deal with the wall to floor junction, how the insulation is continued from under the floor to the walls and how the insulation and rain screen is fixed to the structural frame.  It's quite a neat way to build, but I'm not sure that it's particularly cost effective.  I have a feeling that a well-insulated timber frame may well be a fair bit cheaper, overall.

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Hi Daniel

 

While costs can be squeezed, Quick and Affordable are often at opposite ends of a compromise scale, and to an extent you choose your place along that scale by the decisions you make.

 

It would be interesting to compare numbers with the current costs for Walter Segal style builds.

 

Ferdinand

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Probably @Crofter house is the cheapest being built here as he's doing everything himself. He is also building under the "portable building" (caravan) legislarion so he is exempt from building control.  You might want to take a look at that option as it's not a million miles from what you want.  In Scotland a portable building can be up to 100 square metres. In England and Wales it can be a bit larger (but I don't know the exact size) because the Caravan act in England and Wales got updated at some point but not in Scotland.

 

If you find you can live within that size limit, that is a way to shave off some of the build costs. You might be able to get a more eficcient use of space as you would not have to comply with building regs accessibility and circulation space rules.  the downsize is you might not to be able to reclaim the VAT as you won't have a conventional completion certificate, and I don't know of anyone that has tried reclaiming the VAT with any other paperwork instead.

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Wow @ProDave that sounds really interesting... Are there any links here to @Crofter's house? I'm really keen to check that out....

 

I heard these properties can be put on the green belt because planning permission is not required, nor is there are building reg restrictions, so land is obviously very cheap. I'd certinatly be interested in looking into that, whether it is a portable building or not, I don't care, so long as it fits the bill of affordable housing for people.

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To date my build is at £108,000 and the only thing left to do is the drive. I have just got a lorry load of granite chippings spread over it for now.  I haven't even priced it up yet but if I allow £7000  for tarmac just to keep the figures easy to work with my cost is £522 per sqm. Mine is a 220 sqm chalet bungalow in NI  and as Jeremy said bar the electrics, plumbing and wet plastering and had a hand with the roof I done the rest. Took 2 long back breaking years and near killed me with exhaustion but I can enjoy it now. 

I got the site for free as i built in my parents front garden which helped a lot.

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8 minutes ago, danielclarke said:

Wow @ProDave that sounds really interesting... Are there any links here to @Crofter's house? I'm really keen to check that out....

 

I heard these properties can be put on the green belt because planning permission is not required, nor is there are building reg restrictions, so land is obviously very cheap. I'd certinatly be interested in looking into that, whether it is a portable building or not, I don't care, so long as it fits the bill of affordable housing for people.

 

@Crofter's blog is here:

 

There are a fair few myths about what you can and cannot build on Green Belt, and the starting point is that there is a presumption against building, erecting, or parking any form of dwelling.  Getting permission to put something on Green Belt would be pretty time consuming and costly, so is not really an option if you want to keep costs down, I think.

 

Have you actually got a building plot?  If not, then that's going to be the first hurdle, as it can take a long time to find a plot at an affordable price, especially in some parts of the country.  In high housing demand areas, the majority of the possible plots have already been developed, and despite slight loosening of the planning restrictions, it's still near-impossible for a self-builder to gain planning permission on land that's outside the development boundary.  The big developers can do it, as they make substantial payments to local authorities, which, in effect, means there is a net benefit in terms of revenue that the local authority can use for infrastructure, education, etc.

 

There are some self-build cooperatives around, where groups of people have got together to build a small development, at an affordable cost.  There are significant advantages in this, as it allows the sort of housing density that local authorities like to see for affordable housing (something that can be hard to meet for a single self-build) and the costs are reduced because of the economy of scale (it's generally a lot cheaper, per house, to build ten houses on a site than one house on a site).  If you can't find a local cooperative, then you could, perhaps, look at starting one.

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As @JSHarris says, a portable building does not exempt you from planning permission. It exempts you from most aspects of building control but you still need building control for the drainage to serve it.

 

There's a program running on Channel 4 now by Sarah Beany, how to live mortgage free. I think a lot of the advice she gives on that program is misleading. In one case she said it's easy to get permanent permission for a portable building on agricultural land, and another one she said they don't need planning permission at all as they are not going to live in it forever. I am not sure either of those is true.

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Hi Daniel, welcome to the forum.

I'll echo what the others have said about your target budget being highly ambitious. Does it include site prep and services?

 

A quick summary of my own build: As Dave says, it's legally a 'portable building' rather than a house. This has the advantage of making it exempt from any building regs which makes the DIY approach to design and build much less scary. It also opens the door to various unusual construction methods or features, and would allow you to skimp on things like insulation, activity space, disabled access, airtightness testing, etc. Most of these things are in the regs for very good reasons though- so apart from not doing a formal airtightness test, and not having a disabled access ramp, I'm not aware of having cut any corners.

 

The downsides, however, are significant. To stay within the definition, the house cannot be more than 6x18m, and the ceiling can be no more than 10ft high. It has to be capable of being built in either one or two modules that can be lifted, craned, towed, etc. So therefore you cannot have a slab foundation- you must have a suspended floor. It has to be a bungalow (unless you are only 3ft tall). There is no completion certificate, so no VAT reclaim, and probably no chance of getting a conventional mortgage secured on the property. Indeed, as movable property the kind of loan you would be looking at would be more like you would have for a car, boat, etc. In effect this will have a substantial impact on the eventual market value.

 

I was in an unusual position where all these factors were bearable. I did not need finance from a bank, my site suited a building on piers, and as a second home I wasn't going to be eligible for VAT reclaim anyway. My plans for the future do not involve selling the house, and I wanted to do all of the work myself.

 

My total budget comes to a little under £40k, which includes high-than-average site prep costs. I had to do a lot of breaking out of rock to build up an access, had to import several loads of stone at eyewatering prices (you're probably not as far from your nearest quarry as I am), and spent more than average on the sewerage system, due to ground conditions and usage pattern. Add in the other services and associated fees (road crossings etc) and my 'non building' costs come to close to half my total spend. That leaves me spending £20k on a building that is 52/43m2 external/internal. This budget includes notional figures for internal joinery, electrics, bathroom, kitchen, flooring, but not plastering/painting. I also budgeted materials only for the electrics so, having chosen to get a sparky in, I will be going a bit over budget. I'm probably going to overspend a little on both the kitchen and bathroom as well, so in the end I will probably be just over the £40k. I could have saved maybe £1.5-2k by going for cheap UPVC windows, saved at most £1k by going for minimal insulation, and saved another c.£1k each by deleting the woodburning stove and MVHR. A lower roof pitch would have saved some money but I never costed that option.

 

 

As Jeremy notes, planning in the SE is tricky. Just in case you aren't aware, planning and building control are two totally separate systems. I am exempt from building regs but still have planning permission for a conventional house. I didn't say anything in my planning application about construction method, and just called the property a 'dwelling'. The planners want to know two things: what it will look like, and what the impact will be on local services like roads etc. So they care about how many people will live there, and whether it will be permanently occupied or not. They will care about whether it will be a permanent structure or not. But they don't directly have any interest in construction methods, which are the realm of building control.

 

 

As to your own build: what has started you down the road of steel frame? If somebody was to ask me to build the cheapest possible new build with acceptable thermal performance, I would use a timber frame with steel roof sheets as the cladding. I found that corrugated steel cladding cost about the same per m2 as larch sourced directly from the sawmill, and it was far easier and faster to install. Obviously too early to tell which will last longer, but my larch is fairly low grade locally sourced stuff and I am budgeting to treat it every few years. Whereas the steel sheets have a 20yr guarantee and a PVC coating on them which looks very tough.

 

You're probably right to go open plan, as hallways and extra partitions require more space and materials. Also I think you're right to avoid brick and blockwork. You don't need expensive things like woodburners, huge and complex glazing, or high spec kitchens and flooring.

 

Good luck, and keep us posted.

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@JSHarris no plot yet, i'm in the process of looking. Obviously the cost of land is not included in my budget. I'm in no rush  as I'm still trying to develop the build plan. TBH I was never seriously considering green belt, but the idea did catch my interest when i read it. It's been known to be a nightmare to do anything with, and whats worse, it isn't illegal to sell land you know cannot be built on, and a lot of people still market it as potentially build-able knowing perfectly well that it is not. So when I find something I'm seriously keen on I'll sit down with the local authority first.

 

You've given me a great deal to think about though and I do appreciate that, thank you. In all honesty I wasn't sure what to expect on this forum and so far you've all been great.

 

@ProDave I have been watching that 'how to live mortgage free' program and it is incredibly misleading, I actually think that's where I got the idea of building on agricultural land! In truth, whilst it sounds great, I think i will avoid the portable home route. I want to create something that is mortgage-able so it is a realistic option for first-time-buyers, etc.

 

@Crofter your project sounds absolutely amazing and i salute you on pulling that off - great achievement! It doesn't really sound right for me personally though as my hope is to build a product I can eventually sell at a return. The first build will be for myself and family - if i can achieve a build anywhere near my budget target then I'll look to productize it. I want 80-100k all in, including services, suites, etc.

 

What started me down the road of a steel frame is this - though i found it to be a little misleading, i still feel the concept is a great one.

http://www.walesonline.co.uk/news/wales-news/grand-designs-style-house-costs-just-7945802

 

To answer your first question, the budget does include site prep but not services.

 

 

 

 

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That 'Barnhause' design looks familiar, I think I might have read about it a few months ago. Some nice ideas in there (steel cladding!) but I wonder what you get for £41k- from the article, it sounds as though it may be a bare shell lacking insulation etc. There are some pricey features too, though, notably those huge and presumably bespoke gable windows.

 

Fitting out to a habitable, and building regs compliant, standard is a huge portion of the total cost. See @JSHarris's figures comparing the cost of a wind and watertight shell and the total finished cost.

 

Thanks for the kind comments on my own project. It's become a bit of a labour of love, but being so small has meant that progress has been fairly steady. It was tempting to go bigger- I could probably have doubled the size for around £10k- but working on my own I think I would have got too bogged down by the scale. Maybe the next one...

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I think the "£41k to make" is the give away with the Welsh houses.  Our basic house only cost around £53k to "make", the bulk of the cost is in all the other stuff.  Site costs can be high, especially for self-build plots, as often these plots are only available to self-builders because they have site costs that are too high for a builder to be able to make a profit on.  Often the plot cost is reduced because of this, but as the supply of plots is a lot lower than the demand, there is still a "self-build premium". 

 

Our plot is, perhaps, at the extreme end of this phenomenon.  It's a small plot, just 35m x 16m.  It would have an open market value here in the Mid-South West of around £150k.  We paid a lot less than that for it, because it needed around £56k of ground works, just to get a level bit of land to build the house on.  On top of that was another £12k to get a water supply (initial quote was nearly £24k), just under £4k to get the electricity sorted and around £4k to put in a sewage treatment plant, as that was cheaper than the ~£18k to connect to the main sewer.  So, before we'd even started the foundations we had incurred site preparation and services costs of around £76k.

 

Land prices around here are a bit lower than in the South East, so much so that when we were plot hunting we drew a line on a map from around Oxford, South as far as the coast at Southampton, and only looked in areas to the West of this line.  We pretty quickly realised that we couldn't really afford to buy a plot East of this line, so just excluded that area completely, even though we were living practically on that line at the time.  We had around £150k to £180k available to buy a plot, and were only looking for enough space for a 2 bedroom house with a small garden.

 

 

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@Crofter he uses straw bales for insulation - i hear they're only 70-80p per bale, super cheap, but a friend recently reminded me how much of a huge fire hazard they are! I certinally won't be using that, regardless of how cheap, efficient or eco friendly they are.

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Straw bales have a lot of advantages, and if encapsulated inside the structure aren't a significant fire hazard.  The secret is to stop air getting at them, which you have to do in a house, anyway, to both make the house air tight and provide a vapour control layer on the inner surface. 

 

The advantages of bales is that they can provide a reasonable level of insulation, they are reasonably priced, they have a fairly high decrement delay (which helps to stabilise internal temperature) and they are pretty quick to build with.

 

The only real down side with straw bales, particularly for a small house is that they are big, and need to be to give a decent insulation level, so the walls end up being around half a metre or more thick.  This reduces the amount of usable space inside the house, to a greater extent than for a larger house.  Having said that, the 300mm of cellulose we have in our timber frame walls also ends up making the walls pretty thick; I think our walls are around 430mm thick overall (we don't have any masonry on the outside).

 

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I wired a straw bale house many years ago. I was very impressed with the insulation. I was working in the house in the middle of winter, snow on the ground outside and it was cosy and warm in the house. The only heating on, was a tiny electric fire in the middle of the main room downstairs, doing a good job of keeping the whole house warm even upstairs, and that heater was not even on all the time, it was clicking on and off on it's thermostat.

 

This one I did, they encased the bales in a twin wall timber frame with OSB on the inside and outside, air tight membrane on the inside then a service void, and timber cladding on the outside.

 

The only issue with regards to services, was the few places cables had to go through the walls, they were put in conduit (and sealed to the air tight layer.)

 

I recall there was a concern about the dryness of the bales. They wanted them much dryer than you would perhaps want otherwise and they had to choose (or were lucky) to get a decent dry spell for the straw to dry in the field before being baled.

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Aren't you supposed to treat bales with a borax fire retardent? Or maybe I'm thinking of sheep's wool.

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1 minute ago, Crofter said:

Aren't you supposed to treat bales with a borax fire retardent? Or maybe I'm thinking of sheep's wool.

 

 

I'm not at all sure.  Blown cellulose insulation is treated with borax, I believe.  As far as I can tell from a quick search, it looks like straw bales are inherently fire resistant when incorporated into a structure:

http://www.sustainablebuild.co.uk/constructionstrawbale.html

http://strawworks.co.uk/faqs/

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3 hours ago, ProDave said:

This one I did, they encased the bales in a twin wall timber frame with OSB on the inside and outside, air tight membrane on the inside then a service void, and timber cladding on the outside.

 

Sounds like a potential fire hazard if there's a space between the un-plastered bales and the OSB - a nice chimney. The generally accepted way of making bales fire resistant is to plaster both sides thoroughly to make sure that air can't get to the surface.

 

Some years ago I built a couple of straw bale huts as temporary accommodation, partly in order to assess suitability for an outbuilding I was going to reconstruct. In the end I decided it wasn't a practical system. The relative cheapness of the materials is outweighed by the much wider foundations needed and the very large amount of labour input to plaster the walls.

 

I've just been disposing of some left over bales on a bonfire, and seeing the ease with which they burn, I would want to make sure any building using them was very carefully plastered.

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32 minutes ago, billt said:

 

Sounds like a potential fire hazard if there's a space between the un-plastered bales and the OSB - a nice chimney. The generally accepted way of making bales fire resistant is to plaster both sides thoroughly to make sure that air can't get to the surface.

 

My recollection was the OSB formed a tight sandwich either side of the bales with no air gap.

 

If a fire has got to the point it has burned through the plasterboard, and then through the OSB to ignight the bales, I think the house is lost anyway.

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I very seriously looked into straw bale construction, back in the early days when we'd just bought our bungalow and had no idea what we were going to build when we knocked it down.

 

It's a genuinely amazing construction method, but I believe it's better in drier climates.  In a wet climate like ours in the UK (especially further north and west), you have to carefully manage keeping moisture away from the base of the external walls.  That means a some sort of raised base and a decent rainscreen (or very wide roof overhangs), which tends to eat away at the relatively low cost of the bales themselves.  

 

In the end, I decided we were doing enough unconventional stuff without throwing a relatively untested construction method into the mix as well.   

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19 hours ago, danielclarke said:

What started me down the road of a steel frame is this - though i found it to be a little misleading, i still feel the concept is a great one.

http://www.walesonline.co.uk/news/wales-news/grand-designs-style-house-costs-just-7945802

 

 

Probably worth having a read through this thread:

 

Although it didn't actually reach any conclusions, there's some relevant opinions shared.

 

If you are serious about using a steel portal frame it would be worth making contact with Ed Green at Pentan Architects, who did the Barnhaus concept. While the concept was a competition entry (which it won) and had such things a straw bale insulation and a notional make price of £41K, that concept has now gone forward to actual builds. Around 18 months ago they'd got planning approved on around 4 units for social housing, with others in the pipeline, so I assume some are now built, or well underway.

 

I'd imagine they've learnt a lot going through the process of turning the concept into real builds.

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Having built a steel framed garage that was bigger than my house, i can certainly see the merit in it. It was 61sqm and came in comfortably under £25K all in, even with fancy doors! And serious foundations, as it was on clay near trees. All insulated cladding and insulated base. Ok, the walls and ceiling would need the thicker panels to comply with regs for a house, but the additional cost of that would not be great.

 

Given the cost of the foundations, which was a good part of it, brings me to my question with a steel framed structure, why have foundations? Some type 1 to the necessary depth and a steel frame secured to the ground with some sort of anchor system....................................

 

Taking out the usual foundation systems would surely take out significant cost?

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