Structurally Insulated Panels

I haven't had a chance to post anything here this week. There's been a lot of change!

We decided quite early on that we'd like to build using Structurally Insulated Panels (SIPs). They have excellent insulation properties, by nature they make for an airtight structure and they are manufactured in a factory and then assembled on site = very quick build time.

Our panels have been manufactured by SIPs UK in Northants. Using the architectural drawings they sketched the house in 3D and designed the panels from this.

3D view from the back of the house.

Nick paid the factory a visit in August. This is the boss man, Nigel, and some panels. They are constructed using two boards of OSB (oriented strand board - looks a bit like chip board to me) - these go in a gig and a polyurethane foam core is blown in between. Some sort of magic goes on and the foam bonds to the board. No glue required apparently. And there you have it: a strong, light, insulating, board and foam sandwich. 

The fitting company, Regal, came on site on Monday and have been fitting all this week. There's been a couple of small snags meaning they're a day behind but they've been hard at it and we now have some ground floor walls! It's been brilliant this weekend wandering around the spaces - able to really get a feel for the dimensions of it all.

The Kato crane!

Pesky earth wall dressed in blue.

Most of the joists are in place for the 1st floor. Through the window opening you can see the big pile of bean bag things. They'll be strategically placed when the team are fitting the roof, the idea being if anyone falls off the house/scaffolding they'll have a soft landing!

Work on the second part of the earth wall starts again on Tuesday. It's been lovely to have a break from it this week and not really looking forwards to the last bit - too many anxieties about it all. But ... the first bit went well, looks great and is drying nicely so we're carrying on for the full 5 metres. 

Half way there ...

Shuttering came off the first lift of the new wall on Friday. It's now Sunday and it's still standing ... phew! Nick, Neil and Michael were the ramming team Thursday and Friday. Everything went well and we have been admiring our wall as it starts to dry out over the weekend. This afternoon we are building it some protection. Next week the scaffolding round it comes down and the walls and 1st story joists of the house go up - so lots of large objects being moved around the place. We definitely don't want any dings.

Nick and I both have a heavy working week next week and then the 2nd part of the wall begins again on the 31st.

Neil and Michael working on the last layer.

Fresh out of the shuttering.

The wall bathed in sunshine on Saturday morning. It looks a lovely warm yellow colour, the layers and textures showing up nicely.

Scaffolding is now up around the perimeter of the house ready for Regal to start fitting the SIPs panels next week. Our middle bit of scaffolding will come down on Monday. 

Onwards and upwards

Nick tells me my Testing Times post is very boring! Heh heh - sorry about that - was having a nice time talking about crush test results and trying to explain some of our decision making ...

Short version: We're adding cement to the bottom half of our wall. Once it's had a chance to dry it's much stronger (obvious really!)

Tuesday: A reasonable day's ramming. The scabbler broke, and took an hour or so to fix and spent some time in the afternoon putting up the next layer of shuttering. Nick caught up with wayfinding work in the afternoon so just me, Neil and Michael then. 3 people worked ok. Sore hands and shoulders for me though. Progress around 70cm.

Wednesday: Unfortunately I'm back at work the rest of this week. There was a manpower shortage yesterday - Michael wasn't around either. Nick had posted an add in Gum Tree for someone to help (paid) last week which generated several calls. Working on a 1st come 1st serve basis we had a chap lined up. He had sounded ok over the phone but texted first thing to say he wasn't coming. Why, oh why, couldn't he have called the day before? Useless (insert own word here). So a bad start for Nick but he carried on down his list of responders and found someone with nothing better planned for the day!! Progress around 70-80cm.

The wall going up really does look the same as last time. So i'm posting pictures of the wall fallen down instead:

All that work ... in a heap.

Jeremy, our architect, helping Nick dig the next day.

Where the wall gave.

Testing times

This weekend has been all about the numbers. 


After the collapse we sent off a sample of our earth to ESG a company that do materials testing amongst other things. They have run tests for other REW projects so knew what we were looking for. The results came back on Friday and I was able to talk these through with Rowland Keable (builder of many unstabilised REW). It's all been very educational and interesting.


ESG did 3 tests for us. The results are as follows:

Sample 1: Tested at As Recieved Moisture, without Drying (therefore no Shrinkage)

Compressive Strength:  0.18 N/mm2

Sample 2: Tested as Oven Dried

Compressive Strength: 1.8 N/mm2

Shrinkage: 1.3%

Sample 3: Oven Dried, with 7% cement.  6% water added to achieve drop test criteria

Compressive Strength: 0.48 N/mm2

N = Newton (wikipedia def) 

Sample 1: The earth cannot dry in shuttering so when the shuttering comes off the wet rammed earth has to have the strength to support the wall. This strength is what let us down. Interestingly the 7m unstabilised rammed earth walls at the CAT centre in Wales have the same width and were built in the same way as ours (all in one go). Their rammed earth had a wet compressive strength of 0.5 N/mm2. So we would have been ok up to about 3 metres with ours. 

Sample 2: The dry rammed earth number looks better and would be absolutely fine for our wall.

Sample 3: This number was unexpected and sent us into a right quandary on Friday. Unfortunately ESG had left this test til last so it only had 3 days to dry before testing leaving it weaker than the unstabilised dried sample. 

The poor stabilised number didn't make sense and even though we know cement should make things stronger we wanted proper numbers to compare and contrast and know exactly where we stand. So, Saturday morning we drove down to ESG in Uxbridge and dropped in a stabilised block we'd made 11 days ago. They tested it for us first thing this morning. 

We had decided over the weekend that if the number was still less than the dry unstabilised we'd build unstabilised and figure out how/if to do the top half of the wall later, if the number was good we could stick to our (revised) time plan building the first half stabilised this week and the top half unstabilised in a couple of weeks. 

It was a tense wait ... to cement, or not to cement ... but the number came back good: 2.8 N/mm2. And so, we will have cement at the base of our wall. 

We're relieved. We could have gone for a 2 stage unstabilised build but ... we didn't know how effective 2 weeks drying out at this time of year would really be. We probably could have figured out a way to build the top half later - once the house was up - but the house design means there wouldn't have been much headspace to work in at the top which would have made things really tricky. And in the end there isn't a huge margin of error to play with here so we didn't have the stomach for it.

deja vu

REW2 - day 1!!!

Nick and I sat looking at the beginnings of a rammed earth wall just now pondering our experience of the last few weeks. We're on the up - the trauma is fading and we're feeling good about things again.

This morning was spent waiting for test results and then we got going this afternoon only to be foiled by the compressor we hired to run the scabbler (rammer). We fiddled around, rammed the first layer by hand, phoned the plant hire co. and then Michael headed off home. The plant hire man arrived and showed us the button we should have pressed (@*!^) and Nick and I finished another layer after. So ... we're a whole 10cm off the ground!! Not to worry - we have 4 days to get to 3 metres which should be ok, and we can work Saturday morning if we need to.

Neil's joining the team again tomorrow. I'll try to take a picture or two to post although they're going to look very similar to those taken 3 weeks ago but a bit less sunny!

REW2 ... looking hopeful

Plans are on track so far to start the wall rebuild next week.

The earth was collected, taken about 5 miles away to a local company who put it through their big grindy sieving machine and then delivered it back ... all for £300. Seems like a bargain when we think of how long it would have taken to break it all up and put it through Nick's sieving machine!

The foam glass base got a bit chipped when the earth was shoveled away from it. Probably would have been fine but we decided to start fresh, so it's been removed and a new base ordered.

We've made a couple more test blocks to see if there is any point in paying extra for white cement - does it effect the colour? The blocks have yet to dry but it certainly didn't seem to make much difference to the wet colour.

The shuttering has been refurbished by Michael. We have sanded where needed and varnished again. It's going to have a bit more texture than it originally did. The wall loses some texture when the cement is added but it will gain some from the boarding. Should be interesting.

As well as adding cement we are also now hoping to build in 2 stages. This means we can take the shuttering off the bottom half of the wall and give it a couple of weeks to dry while the SIPs co put up the shell of the house. They say they should be able to leave us space to build the top half of the wall and they will then finish the last bit of house/roof around it when we're done.

Our builder is back from his holiday today and Nick is meeting with him tomorrow to talk about the new plan.

Wall woes

So, I was thinking of changing or deleting my last post because we got it a bit wrong. I'm leaving it there for posterity.

Jeremy our architect was a witness to the collapse of the wall and very kindly came along on Saturday and spent a sweltering day (29 degrees) shoveling with Nick.

It was very useful to uncover things because it turns out our mistrust of the foam glass base was unwarrented. In was entirely intact and it became obvious that it was the wall itself that had collapsed. On reflection, and having chatted today with Rowland Keable (whom has been involved with a lot of the largest REWs around including at the CAT centre), we are pretty sure our error was in failing to allow the bottom of the wall to dry before piling on the weight. So the shuttering came off and we had a damp wall trying to support 13 tonnes. Aaaah, hindsight.

It did look great though before it fell:

Lovely layers. (and cement cap)

Archaeology layer.

Majestic. Sigh.

Can't quite bring myself to post the post fall pics just yet. But we are getting over the shock of it all and steeling ourselves for another build. Lots of phone calls today and getting our heads around the cost implications and task ahead. It is a house building rule to have a 10% contingency fund. We thought we might spend it on the garage if we managed to be disciplined enough through the build. But no, we've gone and done a grand designs style disaster ...

Soil samples are being sent for testing tomorrow. We will get a stabilised sample (7% cement added) and an unstablised sample tested for strength so we can work out how much of the wall we need to stabilise to make sure the next one stays up. We have to build quickly as delay = cost for the main build so we don't have the luxury of having a spare couple of weeks to dry bits of the wall. We are also entering into frosty season ... that's the other thing that could put pay to a damp wall no matter how strong it is. Hence, we will most likely stabilise the bottom half and leave just the top unstabilised. Still organising everything and checking costs but this is the plan at the moment.

REW1 - R.I.P.

What a week.

I've had a busy week back at work. Nick had a really good couple of days ramming Mon & Tues with friends helping and they finished on a high on Tuesday.

But ... our foam glass base has failed. We were using it as a thermal break - so the cold from the slab couldn't travel up the wall. It has massive compressive strength, but we were warned to be careful on the first few levels of ramming as it does not withstand point impact. We were careful. but ...

Nick and Michael were taking all the shuttering off yesterday and I had a lovely telephone call at lunch time - the wall looked amazing. The undulation of the layers was nicely visible, the archaeology looked great, the finish was fantastic. But it turned out that the bottom layer of shuttering and rib had been preventing the damaged base from moving and as soon as it came off the wall fell.

I can't imagine what it must have been like for Nick watching all that hard work topple. It was pretty devastating seeing the aftermath on my return.

There's a few things we're glad of:

• no one got hurt
• it happened straight away - not later
• we went unstablised so we have a pile of earth, not concrete to sort out
• it was freestanding within the house so our design and build is safe without it
• we know that the rammed earth part of our effort at least worked brilliantly

The plan at the moment is we will make a whole lot of calls on Monday and see what the implications are of holding the build up for a couple of weeks and see if we can start again. sigh. Our architects are looking into a different type of base - probably engineering blocks or similar and we will put up with the thermal bridge. And poor Nick has got up early this morning to go and start moving the earth again. 

We're both feeling the weight of disappointment and failure. I'm really hoping we can build it again in the next few weeks. The thought of all that work and stress again is awful but in the long run I think it will feel like much more of a victory. So, on we go.