When I bought my plot I wanted to build a closed timber frame, passive house on a insulated raft with 3G windows.

Unfortunately redundancy, ill health, nightmare groundworks (14m x 4m retaining wall), 3 close bereavements and a lack of a mortgage have impacted my plans massively.

The retaining wall is now finished and I’m ready to start building.

I planned to use ICF blocks and DIY the build with some joiner friends, thinking this would be the best option as I’d save on labour.

When the quote came back, I realised I could have a block house built for less than the price of the blocks.

To keep cost down I looked at 140mm solid walls with EWI. It seems that BC don’t like this idea, nor do any builders I’ve spoken too. So 215mm (100mm block laid flat) make sense from a cost point of view.

I would insulate the walls myself with a timber clad finish.

I’ve read that insulated raft foundations work out cheaper than insulated strip foundations but this isn’t what I’ve found so far.

Any advice would be greatly appreciated. If I have got anything wrong I’m happy to be corrected.

I know most members are interested in building the most energy efficient houses possible. Due to my budget this isn’t a option for me unfortunately. But I’d still like to build the most energy efficient house I can.

The house is nothing exceptional. A 12.5m x 6m 4 bed detached box.

Initially it was 7.5m wide but the width of the retaining wall foundation eat into my plot.

I did finally get some good news this week regarding my plot though.

When I initially bought the plot my solicitor was shut down by the law society before he registered it in my name with the land registry. No one informed me and the guy I bought the plot off remortgaged shortly after.

As a result the land registry initially rejected my completion certificate. It only took my conveyancer 3 years to resolve. I got the call on Tuesday.

Posted By: Kev.kI would insulate the walls myself with a timber clad finish.

I would have thought that the conventional EWI render finish would work out (much) cheaper than timber cladding and possible to DIY.

Assuming you are a building trades novice;
If you get final approval for a basic block-work construction and consider DIY-ing it, my experience is....don't. Unless you are fit, active, and have, PLENTY OF TIME, plus a degree of bricklaying skill, your time will be better spent project managing and supervising. Throw you hand in, if required, doing labouring jobs, this is useful as you'll pick up skills by osmosis.
An experienced block-work team will have the walls up in no time at all. Better to use your time managing material supply, and monitoring all the thousand and one other aspects of house build, that could slip through the net.

Time means money and with that in mind do the same as above for roofing joinery, and roof tilers. Get the shell up ASAP and then "enjoy" the interior and exterior finishing stuff yourself.

Thanks for all the replies and advice.

I have no intention of laying the blocks myself, or doing the roof. It is cheaper to buy the blocks and have them laid than it is to buy the ICF blocks. I will be fitting the kitchen, bathroom and doing most of the interior work myself with assistance.

The original plans were drawn years ago, the layout has been changed due to the width of the retaining wall. It was impossible to engineer a solution as it is in the original plans.

I didn’t not go into detail re the 140mm solid wall. The bco, every builder and se I spoke to did not like the idea. It seems cheaper to do it in 215mm as no one will take the job or even design in 140mm. I imagine it could cause. Issues with mortgages further down the line.

When I priced EWI with render it was horribly expensive no doubt due to government grants. The “expert” fitters were mostly kids who had attended a 2 day course. It just seemed like the latest eco con job to me. I also seen a few examples that had aged awfully.

I like the idea of EWI with timber cladding as I could diy it with a friend who is a joiner.

Maybe a 300mm cavity wall is a cheaper option?

<blockquote><cite>Posted By: owlman</cite>Kev.k :-
" Maybe a 300mm cavity wall is a cheaper option? "

You may well be right, factoring time etc. into the equation, esp. as it's something the brickies know how to do, and therefore gives you a wider choice of sub contractors. It'll satisfy BC etc. so no delay and no reason not to do it in block/block with no fancy time consuming pointing, so fairly quick also.</blockquote>

Cavity walls make no sense to me but if it’s the cheapest option it works.

Would make EWI a lot cheaper too as I would go with 50mm.

I can't see how a cavity wall would be cheaper. (IMO it shouldn't be) In addition you will need wall ties for a 300mm cavity (availability?) and you would have to watch the builders like a hawk to make sure that the insulation had no voids and was put in uncompressed and without gaps around the wall ties. At least with EWI you can see the insulation before it is all hidden by the render.

If you are putting in a 300mm cavity why have the EWI at all? Most of the EWI cost in the UK is the labour. 200mm EWI isn't 4 times the price of 50mm 'cos the adhesive, render coat, mesh and finish coat is all the same. All you have is an extra 150mm of EPS (over nere EPS is priced by the M3) plus a bit extra for the longer mechanical fixings if you are using them

<blockquote><cite>Posted By: Peter_in_Hungary</cite>I can't see how a cavity wall would be cheaper. (IMO it shouldn't be) In addition you will need wall ties for a 300mm cavity (availability?) and you would have to watch the builders like a hawk to make sure that the insulation had no voids and was put in uncompressed and without gaps around the wall ties. At least with EWI you can see the insulation before it is all hidden by the render.

If you are putting in a 300mm cavity why have the EWI at all? Most of the EWI cost in the UK is the labour. 200mm EWI isn't 4 times the price of 50mm 'cos the adhesive, render coat, mesh and finish coat is all the same. All you have is an extra 150mm of EPS (over nere EPS is priced by the M3) plus a bit extra for the longer mechanical fixings if you are using them</blockquote>

Logic doesn’t apply to building in the uk unfortunately. The rest of the world think we build a house twice which is true.

Cavity walls are the norm so cheap and cheerful brickies are more comfortable with them. If i take this route I would have the insulation blown in. Brickies hate the boards and you are right about the gaps.

If I could diy one of the render systems I’d consider it, but the cost installed is ridiculous. Government grants mean the price goes up by 300% and they employ direct salesmen.

I’m planning a timber clad exterior so thought I may as well add a thin layer of insulation.

My plan is to keep skilled trades to a minimum. I couldn’t render a house well, but I could clad one.

<blockquote><cite>Posted By: tony</cite>tonyshouse has a 300 wide cavity, full plans, videos, even things that went wrong ,<a href="http://tonyshouse.readinguk.org/" rel="nofollow">http://tonyshouse.readinguk.org/</a>

My costs we very low and reported but I did half the work myself but paying myself as much as my solicitor earns it still cost less than major house builders figures, all reported but nearly ten years ago.

I would get an engineer to design a cantilevered structure over the foundations to this retaining wall</blockquote>

Thanks for that, I appreciate it.

I had a nightmare with the wall.

Gabions, 2.5m wide and much more expensive than I imagined.

Soil nailing, £70k and legal agreement with neighbour.

King post, £8k design cost and 12m columns.

Timber crib, £60k

Poured concrete, 65k.

Block and steel, £55k.

When I bought the plot I had a good job and a mortgage in place. These quotes meant that I would have to sell the plot. Until I discovered concrete Lego was surprisingly cheap. Down side is 1.8m width at the base.

It wasn’t a easy job, but it saved my build.

If you're comfortable with basic joinery buy a chopsaw, a pile of C16 RS sticks and site build in timber frame.

We built timber frame but to paraphrase someone on here earlier essentially 'built the walls twice' as we had CLT inside for aesthetics and then a non-structural 'larsen truss' built from engineered joists to hold the cladding out far enough to insulate.

With a bit more time for structural design and less budget, we might have used the timber I-joists structurally instead and then just sheathed each side out. You can then blow insulation in or fit between the studs.

No connection to this company but they appear to offer what I describe above as a 'system' option: http://www.phhomes.co.uk/ph15-system/

I know the raw materials on our joists came to about £6k delivered, so you ought to be mainly paying for the structural design and then labour of getting them into place if you can't do this bit yourself.

Don't know if that's of interest but it sounds like it could be a relatively affordable route for someone with joinery contacts.


p.s. I feel your pain with the retaining wall - we had to do three of them to a height of 2.5m x 60m in total. It nearly bankrupted the project before we'd got out of the ground!

I’d find that a bit daunting tbh.

If you can cut wood to a few mm accuracy and knock a nail in fairly square, its straight forward to build frames. We had a timber engineer do structural calcs for the overall building and provide generic detail drawings for window, door and corner construction. Any joiner would be able to do it and DIY following the drawings was a breeze.

Posted By: Kev.k

I’ve been looking at the i joist system DT mentioned. I like it a lot.

I have the same I-beam frame construction on my house and I was told by the structural engineer that a limiting factor was you couldn't have a shallow angle on the roof. My house was the second built in the country and was in 2010. The ph15-system seems to have been a development of the construction method used nine years ago.