Eco-Roof Layers – What Goes Into an Eco-Roof


In the last post, we figured out the correct height and angle for the new roof, in preparation for the roof beams. This post explains more about the many layers in an eco-roof, as well as more problems we encountered.

These Steico beams aren’t easy to fit at all. After discussions with the architect it took ages for the builders to measure and discuss fixings, and then measure again. This has to be exact. There is a lot of thinking ahead on this build. The placing of the fixings are crucial – it is astonishing how much power there is in a gust of wind, and a gust of wind could take the roof off if we get it wrong.

These beams will eventually form the area for the warmcell insulation to be blown into. They will also be the main structure of the roof that everything else will fit around. This means the roof is taking ages to make, requiring a lot attention to detail. All the Stecco Beams have to have the gaps where they intersect filled in with small bits of wood.


Coping with bad weather during a build

We ran into a patch of bad weather. It rained on and off for days just when the builders were working outside and the roof was off. They tried to keep going with building the new eco-roof, but driving rain made it impossible. It was so frustrating to see everything have to stop again and my house with no roof, eco or otherwise, but instead covered in plastic sheeting while we waited for the weather to improve.

In middle of all this, the Gutex boards arrived. These are an important layer in the eco-roof. They are made of woodfibre, and were going to be screwed onto the Stecco beams over the whole of the roof. I was worried the rain would make the wood fibre damp and ruin it. However, they had been treated, so were fine to be left exposed for up to 3 months. In the end, the boards were only out in the open for about three weeks because the builders managed to work in between bouts of rain. Their commitment meant there was plenty of time to get the boards screwed onto the roof and covered over.


Importance of Gutex Boards

The Gutex boards form the outer layer of insulation for the roof. They are flat solid boards made of wood fibre, and dovetail together all round the sides with tongue and grove joints. This means that if you push them close together when nailing them to the roof the join will be almost airtight. Having said that, we still needed to tape up all the joins with special tape, to make sure we didn’t have any gaps at all. But before that, the sheets of Gutex are screwed together with special screws, much longer than normal screws. There are two lots of fixings: one sort goes in at an angle of 60 degrees and the second at an angle of 90 degrees.


You need a good builder for an eco-roof renovation!

I go to meetings with the builders to sort out these things, and am amazed how complicated and detailed this is. I am so pleased that the builders know what is going on! They are all so interested and committed to making it work – which is exactly what you need on a build of this sort.

We are using a variety of special tapes in different parts of this build, to tape up different types of materials. It is very important to do this properly when building an eco-roof: the more attention to detail the more airtight your building will be. With an old building, you have a built-in disadvantage – you have to deal with what is already there. More often than not (as we have found) this is not straightforward and surprises appear when you strip out the building. If this was a new build it would be far more straightforward!

That’s it for today. I hope you enjoyed this post and next time I will tell you about tiling the roof and adding solar panels – a really exciting step. Be sure to come back and join me on the next post.


Putting I Beams In Place For A New Roof


At the end of my last post the builders had taken the old roof off and saved the tiles, which was a straightforward job. This changed the appearance of the house in a very dramatic way. There has been so much discussion leading up to it I thought it would never happen! But as with everything on this build, I would rather they go slowly and get it right than rush it.


The first job was to place two new metal Rolled Steel Joists (RSJs) across the top of the roof horizontally. This will form the basis of the roof, the position of all the Stecio joists will be determined by these RSJs. They do have to be insulated to prevent cold bridging, so are sitting on special insulating pads at either end of the building. I mentioned cold bridging in The Main Start of the Eco Build – Unbuilding and Ripping Down. As you can see, concrete blocks hold these RSJs in place. Each RSJ was bolted to the central metal pole.


The height of the attic floor had to be measured before anything was done, to make sure that the finished attic floor will be just below the base of the central vertical pole, and that the roof will be at the right height. This pole holds up the two middle ends of the RSJs.


We are going to raise the height of the roof by about 240mm to allow for timber Steico I beams. Then insulation will be put in between the I beams, exactly the same process as we will use on the back wall of the living room.


Timber Steico I beams are made up of natural fibreboard, which forms the upright bit of the I, and the oblong ends are made of LVL (laminated veneer lumber). This is formed of multiple layers of thin wood with adhesive in between the layers, it is a very robust material and doesn’t warp, or twist like wood can.


I beams are very eco: they use about a third of the amount of timber than if these beams were made of just ordinary wood. The joists are FSC certified (Forest Stewardship Council.) This organisation was established to promote responsible management of the world’s forests.


The I beams will run up the roof at an angle. Fitting these beams is an art in itself. They meet at all sorts of angles and have to have bits of wood to fill the gaps where they don’t quite meet, so all quite fiddly.

The architect needs to tell the builders exactly where to place each I beam, so that the fixings can be put at the correct intervals. This is important, as the big sheets of fibre board, called Gutex boards, that are going on top of the roof can be vulnerable to suction, when there are strong gusts of wind. So the fixings have to be exactly right so that I don’t lose the roof in strong winds!


As you can tell, quite a lot is going on at the moment, and after all that working out where straight is, in the last post, we now have the main structure of the roof marked out in Steico beams. Now we can get on with the rest of the roof phew!