Self-build steel frame barn conversion - almost complete

[mattman]

Hi everyone

 

I just wanted to introduce myself.  My family and I are just coming to the end of a self-build steel framed barn conversion which started back in 2019.  We only have minor things left to do.  I project managed and also designed the entire house and my wife and I did all the planning application.  I'm not an architect - it was more the fact we were left in the lurch by a really poor planning consultant/architect that we decided to take over ourselves and pleased we did.  Our house is fairly standard block and brick masonry cavity-wall construction and we have quite large 150mm block cavities (concrete blocks for the external skin and thermalites on internal skin) full-filled with 150mm breathable mineral wool insulation, plus a further 50mm waterproof mineral wool externally behind cladding (crucially still allowing plenty of ventilation behind cladding), 100mm PIR celotex in floor (would have done more in floor but we're limited by potentially low ceiling heights), 200mm PIR celotex warm roof with an airtight VCL.  We had a builder build our foundations and shell and he also put up some plasterboard on internal walls, we have a full wet plaster on all external walls.  We had a separate roofing company do our metal roof, a cladding company have done our larch cladding and electrician and plumber are close to finishing our second fix items. My wife and I took over from the builder after he left.  I then spent many weeks applying a cement lime "parge" coat on the inner face of all external walls (prior to our plasterer doing the full wet plaster), and I applied air tight tape everywhere in an attempt to make the house as airtight as possible - it was hard because our builder did not see the importance of air tightness.  I've also built an exposed brick wall spanning half the entire downstairs and we also fully prepared the entire groundfloor for our concrete pour - doing the insulation, membrane and steel mesh etc, as well as doing some of the insulation and VCL in the warm roof.  We had a concrete company pour and  powerfloat the concrete slab which acts as our finished floor surface, as well as being a good thermal mass.

 

Our house is heated solely by an 8.5kW ASHP and costs very little to run, which does all our hot water and our space heating, via wet underfloor heating in our concrete slab on the ground floor (no heating upstairs aside from a couple of electric towel rails).  We also have solar thermal tubes which isn't doing much at the moment with the cloudy rainy weather and we also have 7.6kW solar PV on our roof which will be connected to an inverter and batteries later in the year.  We also have MVHR.

We just had our air tightness test done and we scored 2.5 m³/hr.m² @50Pa for the standard air permeability air tightness test, and 1.96 ach/hr @50Pa under a passivehaus air tightness test (although I can't use the Passivehaus test result for my SAP calcs). Dealing with non-straight original timber roof perlins and other characteristics in the original barn, and being masonry construction meant getting it air tight was a challenge.. plus it was a bit of a battle dealing with most of the trades who did not understand the importance of air tightness - our main builder thought we would never be able to open our windows!  And it was solely me doing any kind of air tightness work. I'm not sure if 2.5 for a masonry house is ok or not??  I had hoped it might be slightly better after all the time I spent but I'm glad it is lower than 3 though because we have an MVHR and these work better at 3 or below (and at the end of the day it is just a number).

House appears to stay warm, costs virtually nothing to run, no mould or condensation thanks to the MVHR which also evenly distributes the warmer air downstairs to all rooms upstairs, so overall really happy.  It's been a lot of extremely hard work, especially with three quite young daughters, and working full time.  Sorry for the long introduction.  Attached is a pic.

Matt

[Gone West]

Welcome to the forum. Well done, it's a nice looking house. Any more pics?

[mattman]

Thanks for your reply.   Here's a pic from a few weeks ago.  It's still a bit of a mess.  

[mattman]

It used to be an agricultural steel shed.  What kinds of air tightness scores are people getting on a masonry build?

[SamSmith]

Great job, a lovely building.  Would love to see a picture of your power floated floor?

[IanR]

Hello @mattman, and welcome!

 

Lovely project. I did very similar myself, starting in 2016, although with a timber frame rather than masonry.

 

You appear to have put your PV on rails. What did you connect the rails to the standing seam with? Did you consider fixing direct to teh standing seam, without the rails. I've not made my mind up yet, so am yet to install PV.

[Beechgate]

You're meant to join at the beginning of the project so we can follow along!

 

On a serious note it looks great, so well done and congratulations!

 

I'd also be keen to see pictures of the power floated floor

[mattman]

18 hours ago, IanR said:

Hello @mattman, and welcome!

 

Lovely project. I did very similar myself, starting in 2016, although with a timber frame rather than masonry.

 

You appear to have put your PV on rails. What did you connect the rails to the standing seam with? Did you consider fixing direct to teh standing seam, without the rails. I've not made my mind up yet, so am yet to install PV.

 

Thanks. Do you have any pics of yours?  We were lucky enough to inherit half of this barn in an amazing spot (my brother-in-law's family inherited the other half, so it's a semi detached barn conversion - luckily we get on really well!  However next on my DIY list is landscaping - garden fences, small trees and walls, so we can make it more private as it is all a bit open outside at the moment). We each sold our houses and financed the build of both halves - lived in a static caravan on site for two years.  

Regarding our solar panels I'm pretty sure from memory they were "S5" clamps and Renusol rails.  I'm not sure why we put them on rails - our installer specified the rails - I think possibly because it gives a bit more breathing space above the metal roof, as it can get quite hot to touch in the summer - although the DC cables are touching the metal roof so our electrician seemed to think it would be fine - I think using the rails made it easier to line up where we wanted the panels etc.  We don't seem to get many birds on the roof but if we do I will have to have some kind of bird proofing put on too.  We plan to get them connected to an inverter and battery storage in the next couple of months hopefully. Just waiting for our G99 application.

[mattman]

Thank you for all the kind words from everyone.  I should definitely have started posting when we started the project - time flew by - it was very hectic most days, doing my day job full time and also trying to manage the build as best often late in the evening/nights), and also spending time with and looking after our children.  Not sure how we did it.

Here's a pic of our floor. It looks a bit "rougher" (not quite as shiny) in person but we like it and all its imperfections.

 

[mattman]

Another pic:

 

[SamSmith]

Thanks for the pictures. It's something we may consider as the costs for polishing are now in the realms of ridiculous. 

We prefer a more matt finish and the imperfections will hopefully give it more texture.

[IanR]

10 hours ago, mattman said:

Do you have any pics of yours?  We were lucky enough to inherit half of this barn in an amazing spot (my brother-in-law's family inherited the other half, so it's a semi detached barn conversion - luckily we get on really well!  However next on my DIY list is landscaping - garden fences, small trees and walls, so we can make it more private as it is all a bit open outside at the moment). 

 

Here's ours, been in for 5.5 years now. This pics from a few years back, just after we cleared the debris from the build and started to get it seeded.

 

 

Quote

Regarding our solar panels I'm pretty sure from memory they were "S5" clamps and Renusol rails. 

 

I've settled on going with the S5 also, but am hoping to go without the rails. I'm just looking for a few similar installations to get a bit more confidence in attaching in that way

Edited April 7, 2023 by IanR

[mattman]

41 minutes ago, IanR said:

 

Here's ours, been in for 5.5 years now. This pics from a few years back, just after we cleared the debris from the build and started to get it seeded.

 

 

 

I've settled on going with the S5 also, but am hoping to go without the rails. I'm just looking for a few similar installations to get a bit more confidence in attaching in that way

Looks amazing Ian! I really like the design. 

[mattman]

6 hours ago, SamSmith said:

Thanks for the pictures. It's something we may consider as the costs for polishing are now in the realms of ridiculous. 

We prefer a more matt finish and the imperfections will hopefully give it more texture.

Yeah we got some silly quotes for a fully polished floor. I think I read about or saw a program where someone powerfloated their concrete instead of polishing it and it seemed to be what we were after and less labour intensive so cheaper. We ended up going with a local concrete company who worked with a team who did the power floating, although my wife and I did all the labour to get the floor ready for the concrete pour.. Ie insulation, membrane and the steel mesh. It was half the price of polishing. It is quite an industrial look but the imperfections do give it texture and character. We love it. A lot of visitors comment how they like it too. It does get a few tiny hairline cracks but it actually blends in and adds to the character. For a few weeks after we had it laid it was very "smeary" and blotchy in appearance, like a white haze and I thought we had made a mistake getting it but the haze disappeared after several weeks. It's apparently part of the curing. 

[markc]

Hi, welcome and well done!

[mattman]

Thanks Mark. 

[cheekmonkey]

On 07/04/2023 at 01:56, mattman said:

Yeah we got some silly quotes for a fully polished floor. I think I read about or saw a program where someone powerfloated their concrete instead of polishing it and it seemed to be what we were after and less labour intensive so cheaper. We ended up going with a local concrete company who worked with a team who did the power floating, although my wife and I did all the labour to get the floor ready for the concrete pour.. Ie insulation, membrane and the steel mesh. It was half the price of polishing. It is quite an industrial look but the imperfections do give it texture and character. We love it. A lot of visitors comment how they like it too. It does get a few tiny hairline cracks but it actually blends in and adds to the character. For a few weeks after we had it laid it was very "smeary" and blotchy in appearance, like a white haze and I thought we had made a mistake getting it but the haze disappeared after several weeks. It's apparently part of the curing. 

 

@mattman i was about to post something later in foundations forum.  we want a power floated concrete finish floor in our barn conversion but struggling to work out the slab make up that best works.

we have a SIP build around an old concrete frame barn but it has a fair bit of proposed new steel work to hold it up.  We have proposed ASHP & underfloor heating (single story apart from small mezz)

architect had originally conceived a raft foundation but they expected us to screen the top therefore 75mm - talking to concrete people they say the top coat needs to be more like 150mm. they then said that they dont think that would work with UFH.

my thought at the moment is:
- strip foundations with block/brick stub walls that the SIP fixes to.  (including internal walls) The steels bolt to these walls also, or small concrete pads
- slab make up is then hardcode/sand/membrane/insulation/steel mesh/UFH (on top of mesh to in top part of slab)/150mm concrete that's power floated.  All this can happen after the SIP is built so in the dry & won't get damaged after

No-one seems to want to help advise what's best so i'm at the point to making the choices myself.

Interested to get your experience on this & if you followed a similar make up at all.  TIA  Pete

[mattman]

On 09/05/2023 at 13:37, cheekmonkey said:

 

@mattman i was about to post something later in foundations forum.  we want a power floated concrete finish floor in our barn conversion but struggling to work out the slab make up that best works.

we have a SIP build around an old concrete frame barn but it has a fair bit of proposed new steel work to hold it up.  We have proposed ASHP & underfloor heating (single story apart from small mezz)

architect had originally conceived a raft foundation but they expected us to screen the top therefore 75mm - talking to concrete people they say the top coat needs to be more like 150mm. they then said that they dont think that would work with UFH.

my thought at the moment is:
- strip foundations with block/brick stub walls that the SIP fixes to.  (including internal walls) The steels bolt to these walls also, or small concrete pads
- slab make up is then hardcode/sand/membrane/insulation/steel mesh/UFH (on top of mesh to in top part of slab)/150mm concrete that's power floated.  All this can happen after the SIP is built so in the dry & won't get damaged after

No-one seems to want to help advise what's best so i'm at the point to making the choices myself.

Interested to get your experience on this & if you followed a similar make up at all.  TIA  Pete

 

Hi Pete

 

We are on a raft foundation.  I'm not a builder nor architect but was heavily involved in the build getting my hands dirty when I could (sometimes even correcting things I wasn't happy with that the builders had done).  We are a masonry build so it might be slightly different to your SIP structure I'm not sure..possibly not.  Our raft foundation, from memory, was basically hardcore, crush, sand and then membrane and mesh etc then the structural concrete slab.  The house was then built up around this and when water tight with internal walls done we then prepared for our concrete "finished" floor, designed to be at least 100mm thick but in some areas definitely 150mm.  Thicker is better as it is less prone to cracking and actually also becomes a better thermal mass.  Concrete, I believe (I might be wrong), is a better thermal mass than screed, but on the flip side takes longer to heat up than screed but then holds on to that heat for a lot longer.  The build up of our "finished" concrete slab was all done by myself and my wife (as builders had left by this point) and we first made sure the structural concrete slab was all level (used some levelling compound where we needed it, and then laid our PIR insulation (celotex) directly on top of this.  Then taped it all up (very important as concrete mustn't get through the gaps otherwise the insulation boards could float - this must always be done whether you are using concrete or screed on the top of insulation).  Above the taped up insulation boards we then laid the thick gauge black damp proof membrane, taped up where any joints were in the membrane, and taped up against the walls.  And above the membrane my plumber laid the underfloor heating pipes.  And above the UFH my wife and I spent a couple of days laying "meshmen" (which are supports to hold up steel mesh) and laid steel mesh, all tied together.  And then it was ready for the concrete pour which would act as our finished floor surface - and the same company who did the pour also did the powerfloating, on the same day, literally about two hours after the pour.  In hindsight I would have preferred to have had the insulation and UFH all in the first layer of concrete slab, ie. the structural slab right at the beginning of the build, as it would have allowed a lot more ceiling height and saved the cost of the second concrete slab.  Apparently a lot of passive houses work like this and have just one concrete slab which acts as both the structural slab and also the finished floor slab with all the insulation and UFH in it.  

In regards to the UFH not working in 150mm thick concrete.. it definitely does work but it works differently to what people might expect such as it might with thinner 75mm screed.  It doesn't feel warm to the touch - but it equally doesn't feel like cold concrete either.  Our pantry which has no UFH in it was very cold to the touch, in the winter, compared to the rest of our open plan area which did have UFH on.  It definitely emits heat as when you look at the thermostats the temperature rises (it does take about 12 to 24 hours to change temperature as an ASHP works much slower) or when you walk in from the outside the heat really hits you.  And it also retains heat very well even without any heating on.  During the build before the UFH was operational the house was so warm.  We love it.  The concrete can still get warm to the touch if you raise the flow temperature up on the ASHP.  But you really don't need to raise the flow temperature up at all as a steady low flow temperature is all the house needs to stay warm. We have ours at the lowest flow temperature setting of 25°. We haven't had the UFH heating on for the last three months as the house has stayed so warm on its own.  The ASHP also runs much cheaper when you have a low flow temperature and have it on all the time too (seems counter productive but it works much better that way - and have all the UFH zones on too).  The concrete slab works really well with the ASHP and UFH as it retains and emits the heat really gradually, instead of one big blast - allows it to run really efficiently.  Especially so if your house is reasonably air tight too and has an MVHR.  Hope this helps.  Good luck in your build!  Let us know how you get on.

Edited May 10, 2023 by mattman

[cheekmonkey]

@mattman thank you very much for the detailed reply.  I'm trying to get a all with the engineer today but i've spent a couple of days head scratching & drawing up a layup which is very similar to something I built myself before on a TF building (so really little difference to SIP).  Interesting to hear you would try & incorporate to one slab if you did it again - that's what i'm trying to do else you end up with soooo much concrete for a really lightweight build!

 

I've worked out that the floor has to go down before the SIP really as the DPM layer would have to be laid & ultimately would get trashed no doubt.  There are risks of damage to floor so we will have to board over it but it definitely makes the concrete guys job easier as they would float an open slab. (have to pray for good weather but the last one i did myself i did in October & managed a reasonable finish to the power floating.)

 

My plan/proposal for engineer is:

• 150mm crushed
• sand blinding
• DPM
• 150mm insulation
• slip DPM
• 50mm meshspacers
• mesh
• UFH clipped to mesh
• 150mm concrete powerfloated

We'll see what he says.

Really pleased to hear about the UFH experience you have too.  We have circa 210m2 floor (plus integral garage but wont heat that) & expect we'll have a similar size heat pump to you for DHW & UFH probably jsut split into 2 zones for bedrooms & rest of house & probably similar size solar set up with batteries.  We're used to living in old houses & think we might find the house quite warm without heating on.  We will have MVHR also & a log burner just because we love the atmosphere & warmth from them.  We're also going larch cladding, basically we're copying you .  I was looking at standing seam roofing but our budget is already looking stretched & I might end up going metal sheet profile instead as I can fit that easily with some labour help.

I pushed the button on the SIP build yesterday so that will work into slab detail & starting to dig some holes over the next month or so.  I must start a progress post somewhere to stick up some photos

 

Thanks again, great to hear such a positive experience.

[George]

On 09/05/2023 at 13:37, cheekmonkey said:

architect had originally conceived a raft foundation but they expected us to screen the top therefore 75mm - talking to concrete people they say the top coat needs to be more like 150mm. they then said that they dont think that would work with UFH.

 

You should either go for a fully insulated raft or a screed on top of insulation on top of the raft.

 

If you don't want sand+cement screed (which is essentially a fine aggregate concrete) you should still be OK to go for a 75mm thick concrete, espcially if using 10mm aggregate. You could even go and find some interesting aggregates to add in. I'm not sure why you were advised 150mm minimum - unless they were thinking of the structural raft below. 

 

 

[cheekmonkey]

3 hours ago, George said:

 

You should either go for a fully insulated raft or a screed on top of insulation on top of the raft.

 

@George so why is the raft a must? Why not make the slab structural, insulated & have the heating all in one like my idea?  That way you have a nice mass to heat like Matt had experienced & ultimately a slightly easier construction as less process.

[George]

A structural slab is a raft if it's carrying the walls..

[cheekmonkey]

42 minutes ago, George said:

A structural slab is a raft if it's carrying the walls..

 

Ahhh ok - i see what you are saying... ours does not carry the walls.  I maybe didn't make that super clear.  The perimeter SIP wall will be sat on block/brick on a strip footing, the slab is just a slab

 

From my original comments :

"my thought at the moment is:
- strip foundations with block/brick stub walls that the SIP fixes to."