5 (2 adults, 3 dogs) go building in Dorset

I too am looking at all these systems.

the velox internal wall panels --just don,t use them ,if only non load beating then stud walls?

or use 2 velox panels at thinner size and pour ?

.

where your site  is makes a difference to costings on all  types--due to transport costs --I will be more as in scotland 

Isotex  looks a better made  of block and could be a the one --

I still am looking at one type of poly ICF 

that is ISODOM 2000--looks by far the best poly system and wall blocks are longest,best locking between blocks  --so making straight wall will be easier+ biggest selection of different elements  of any system 

the agent assures me that hire of bracing will not be a probelm ,and inferred it could be included --I may have picked him up wrong

,but same as you 

till I  have a design  I cannot get comparative quote

Isodom agent, ekonect, also build it you wish --they used to be durisol agent -so they are not just salesmen 

 

Edited February 2, 2019 by scottishjohn

Thanks for this very informative blog. I wish you luck with your decision and look forward to this project unfolding. If the blog continues in this vein, it will be of much use to others, I'm sure.

Pat pat, good blog ! Best of luck.

 

>We have no experience of actual building work but let's face it, how hard can it be ? - famous last words.

 

There exists a rabbit hole down which - at some point - you will discover that you have fallen !

 

A bit of extra info for Durisol virgins who just surf-on-in:

 

1 - I think Durisol (and the other one) give stronger concrete structures than you may have implied, as done properly the sloppy concrete infiltrates the matrix of the block.

2 - Durisol is cut with a normal power saw (no guarantee on blade life time ?)

 

 

Credit: http://endeavourcentre.org/2012/06/a-finished-durisol-block-foundation/olympus-digital-camera-29/

Edited February 2, 2019 by Ferdinand

48 minutes ago, Ferdinand said:

There exists a rabbit hole down which - at some point - you will discover that you have fallen !

But I am FANTASTIC at Lego ??

 

49 minutes ago, Ferdinand said:

I think Durisol (and the other one) give stronger concrete structures than you may have implied, as done properly the sloppy concrete infiltrates the matrix of the block.

 

It’s not the strength but the air-tightness that I think will be different.  I know that @JSHarris has previously mentioned that concrete is not necessarily air tight but it has a much better chance than the woodcrete.  The difference between the three products is how complete the concrete wall within the formwork will be.

 

During the Durisol training, they were very keen to talk about the product being breathable.  Passivhaus and air-tightness were almost dismissed as a goal not worth aiming towards.  The MD (a structural engineer) went so far as to state that it made no sense to him as an engineer to make a property air-tight and then introduce an MVHR to bring in ventilation.    They also talked about Thermal Mass and I just smiled sweetly and thought of our Jeremy ?.

 

We went to a passivhaus seminar at NSBRC in November and cat flaps were mentioned.  IIRC they were mentioned in the hundreds of pounds to much laughter.  During the Durisol PowerPoint, a similar cat flap story had become thousands £s.  We have a similar story in our family.  Peter lost £5 in the sea in Cornwall during our first holiday together when we were mere babes.  (17 &19).  This was way before children came along and before the lottery existed.  That £5 is now referred to by the kids as a winning lottery ticket that would have set them up for life if only their dad hadn’t lost it in the sea - it has taken on a life of it’s own ??.

1 hour ago, Redoctober said:

Thanks for this very informative blog. I wish you luck with your decision and look forward to this project unfolding. If the blog continues in this vein, it will be of much use to others, I'm sure.

Hopefully others will find it useful, the danger is that it will be too dry as it is my decision making process as opposed to nice action posts - that should, with luck come

along later.

 

2 minutes ago, Sue B said:

 

 I know that @JSHarris? has previously mentioned that concrete is not necessarily air tight but it has a much better chance than the woodcrete. 

 

 

Not quite.  I've mentioned before that block and brickwork won't be very airtight, unless parged or wet plastered, but cast in-situ concrete should be pretty airtight I'd have thought.  It very much depends on the nature of the ties between the inner and outer skins of ICF, as they are about the only places where there is a small risk of air leakage. 

This is what is was thinking of -  not you @JSHarris but @najem-icf.  “Reminds me of an article I read when I was Stateside some years ago about a Durisol build 22 storey hotel in Canada - built back in the early 1980's - guests complained of "ghosts" in the rooms - later realised it was curtains moving due to air penetration through the structure.”

 

I knew I’d Read something somewhere.

Just parge coating Durisol should fix that easily enough I'd have thought.  Pretty quick and easy to do, just need a bucket and broom.

If you chase channels out on  inside  of wall for your electrics

then hard plaster ,that will do the same .

and if cladding outside ,then maybe house wrap it under the batons for the cladding

but if going rendered that will also serve  to do the same

plenty of good options

should be less concrete cost using durisol  or isotex as they are 120mm concrete -

lot of poly types are much thicker 

 

Edited February 2, 2019 by scottishjohn

Thanks for sharing your thoughts and research @Sue B really interesting to read. I'm just along the coast from you  I think in Boscombe, building in Parkstone.

 

Also ICF enthusiasts, interested to see your concerns re fixing to the walls. I'd considered that and thought that for internal fixings we'd fix structural ply before fixing plasterboard for key areas in kitchen and bathroom. I am thinking now about exterior fixings as after render that isn't so obvious - thinking initially lighting but even simple things like hose reels in garden or in future who knows what. You can of course go through to the concrete but with ~75mm of EPS that isn't ideal and heavy items I'm a little concerned (maybe unnecessarily) about the pressure applied to the wall so will keep researching this. May even have a look at non-EPS/XPS options - we have rear walls which are below ground so need something that is appropriate (of course with waterproofing solution).

Not far at all @Adam2.  I was in Poole this morning and took the opportunity to drive round past the Durisol build there.  Window forms are in so I'm sure they will be pouring very shortly.

in the process of studying dry wall finish  against  chasing wall for electrics + then mechanical spray plastering --

used in europe for years --now plenty of uk companies that do it--will be good for air tightness as well

easy to chase woodcrete --and how often do you REALLY want to add new electric supplies?

ball park figure i,m being told by  an ICF supplier  is around £8 sqm -for spray plastering finished job .

so anyone done a calculation of proper drylining with service void ?

cos with drywall stuck on ,

you might as well go hard plaster 

 

One of our wish list items is wet plaster (possibly spray) as opposed to dot and dab.  Partly because of the air-tightness but more

because I just prefer the finish.

The house will have to have a VCL, and that will be on the inside face of the structure, and that should be airtight as well as being vapour tight.  It worries me when we see poor construction allowing cold air in behind dreadful dot'n'dab plasterboard, as it's not the dot'n'dab that's really the problem at all, it's that the builder hasn't ensured there's an effective VCL.  Houses like this are going to have interstitial condensation problems, I'm sure.

not convinced that an ICF solid wall house where insulation is on outside and keeping solid wall warm ,same temp as room ,or near enough 

and with proper MVHR will ever have the required temp dif of wall and air to get condensation 

 but interested to know how and where you would fit a vcl  on these types of build ?

52 minutes ago, Sue B said:

One of our wish list items is wet plaster (possibly spray) as opposed to dot and dab.  Partly because of the air-tightness but more

because I just prefer the finish.

 

Do you mean the solid feel of wet plaster ..?? I’ve used the new foam adhesive rather than dot and dab and been surprised how solid it feels - you get the speed benefit of the skim coat and quick drying with the “solid” feel with no hollow sound behind the boards. 

The VCL is what it says, a Vapour Control Layer.  It can easily be a part of the fabric and doesn't have to be a separate entity that's added on as an afterthought.  Take our build as an example; our VCL is an inner frame racking skin of Spano Durelis.  In an EPS ICF construction the VCL may well be the inner layer of EPS.  With wood/cement fibre ICF construction the VCL could well be a cementitious parge coat on the inner face, before plastering.

 

A VCL doesn't have to be totally vapour impermeable, it just has to have a permeance that is significantly lower than anything within the build outside it.  The name gives away exactly what it does, control vapour movement, not necessarily completely block it.

 

Finally, as ICF is a sandwich that may well have a significant amount of insulation on the inside as well as the outside (some ICF seems to be almost 50/50) then the concrete core is going to tend to sit at a temperature part way between the inside and outside temperature.  Concrete is a relatively good thermal conductor (around 1.5 to 2 times more conductive than water and around 25 times the thermal conductivity of something like EPS) so it's likely that the core will be at a reasonably even temperature through its thickness with the greatest temperature gradients being through the insulation on either side.

VCL was mentioned during the Durisol course but I didn’t listen as I was busy making notes about another issue and it was just background noise at the time.  However, I will of course be asking Jamie about it later this month during the Isotex training.  

 

Heads up Jamie - you know one ofnhe questions coming your way ?

23 hours ago, JSHarris said:

an inner frame racking skin of Spano Durelis

 

Blimey. That sounds like an STD.

On 03/02/2019 at 10:30, JSHarris said:

Spano Durelis

so how did that compare with osb+vcl  in price --could end being cheaper maybe?.

providing you comparing 12mm osb and not 9mm 

I don't know, as it was a closed panel system that was designed to meet the performance spec and be quick to put up.  The inner panels are 12mm thick, and taping the joints after assembly looked to be much quicker and easier than fitting a separate VCL membrane, particularly as the surface of the inner panels is very smooth, because of the vapour sealant on the outer surfaces of the board.

We have just had the word that the Durisol build near us has the first concrete pour on Tuesday 26th.  Just booked my half day holiday so that we can go there first thing.  Very excited so I can't imagine how they are feeling

 

Edited February 19, 2019 by Sue B

And the pour has been delayed - sturctural engineers disagreeing over what is required.  

 

Today we went to the free training day at Swindon NHBRC for the Isotex build system.  The day was a very similar format to the Durisol training day but the whole day felt less formal and went really well.  The actual hand's on part of the day, I thoroughly enjoyed, I felt we learnt much more about how to actually use this product, including how to fix something that we know is likely to happen (putting a block round the wrong way so that the insulation is on the inside and not the outside).  The issue with this is the break it will make in the concrete honeycomb - the wall will have a weak spot so you have to fix it.  We built over a window frame, cut some blocks, talked about door openings and left feeling quite confident about the product.

 

So now I have seen the 2 products that are in contention in a training environment.  My verdict comes down 100% on the side of Isotex, luckily Peter agrees and I didn't even have to tell him what his decision was!  The reasons for this are really a confirmation of my thoughts prior to the training:

• Less webbing so that the concrete honeycomb is more complete
• Smoother so that they appear to "shed" less
• The pass block which keeps your "brick bond" does make life easier as there will be less cutting of blocks on site.  
• The design of the block increases the air-tightness of the finished wall - Durisol has two woodcrete faces that butt together, Isotex has open ended blocks that fill with concrete, sealing the air gap.
• I felt that the support during a build would be better - that is purely a gut feeling of course, but there is no way of quantifying this without talking to lots of previous self builders.  It was clear however, if we needed a visit, they said they would come out to us in addition to the visit that they actually schedule in to make sure you are getting on ok at the start of the build.

The choice of build methond is one of the more fundamental of any self build and in addition to the quantifiable benefits that have helped us favour this product is the inevitable personal prejudices that we all have regardless of how much we may try to neutralise them.  For me, having the saleperson talk positively about a foundation system that I have only heard good things about on this forum made me feel that they were on the right page with how builds should be today.  Durisol were quite dismissive of insulated slabs.  MVHR - again, Durisol were dismissive, let the house breath and you don't need an MVHR.  Isotex understood the need for air-tightness and therefore an MVHR to give you the ventilation that is needed to keep the house healthy.

 

Our next steps are to visit a site for both product on pour day.  Hopefully we should be able to do this in March as they both have pours quite locally to us.

 

The BBA certification is still rumbling along, however for me it not a particular concern.  If we can get a mortgage and the 10 year warranty insurance, I really can't see an issue.  That along with the fact that we will not be bulding until next year, when BBA certification (for what it's worth) should be in place means for us it is a minor item.

 

So, for us, we have a product in a clear lead, it will come down to real world usage on a site with people like us and of course price.    

 

Finally, it was lovely to see @Tom's Barn again and to meet Karen who is hopefully a member of Build Hub in the very near future.

Hi @Sue B

 

it was great to catch up with you and Peter again - it is becoming a habit and a good one as we share what we know.

 

I agree with you comments about the block. I am wood cladding the exterior of my house so a flush wall to batten is extremely important; an uneven wall at this stage will lead to uneven cladding which is not the look I am going for.

 

I did also pick up the two points about "you must not use":

 

1. Metal hammers to tap blocks into place - rubber mallets are the way forward

2. A drill set to hammer mode. I definitely need to ensure everyone understands this onsite or it will lead to issues fitting my cladding.

 

I did learn the following:

 

1. Mark every block that has been cut / modified so that it can be supported with shuttering during the pour

2. Concrete must have 10mm aggregate not 20mm which is the norm

3. Using spray plaster internally (floor to ceiling) negates the need for an air-tightness layer first

4. Use foam tape around windows to ensure air-tightness ( I don't have a name for this product...)

5. All webs need to be in-line when you look down during stacking. The webs at the pass block step will be slightly out of line

6. Pass blocks help achieve the brick bond need for structural strength

7. Build good quality window boxes with diagonal bracing

8. Cement to be used is either RC30 or RC35

9. From my notes it would seem there is a structural engineering pack for this product (did I get that right?)

 

I thought the training was very good especially the practical element that focused on building a wall and window opening. Completing that small project was important in building my understanding of how the system worked.

 

I received my planning permission yesterday so we are now off and running. However, based on the fact that there is no BBA Cert for this product as yet I am going to have to build my garage of something else if my building control officer states he needs this in order to approve it. Hopefully by the time the main house starts the BBA cert will be in place.

 

If anyone knows of a pour taking place for a ISOTEX build let me know. I am keen to see one taking place for the final piece of my learning.

 

The journey starts here....