Building the Roof (111)

During late August and September, we finally managed to insulate and waterproof our roof. We worked with our roofing contractor, Ed Sullivan, to complete the job. He reckoned that it was probably one of the most awkward roofs he’s worked on! Due to the roof’s myriad planes and slopes, both insulating and waterproofing were time consuming, difficult tasks.

Our roofing system is a warm deck (i.e. the insulation is above the OSB deck) and this brings it inside the building’s insulation envelope. This should eliminate condensation as there should not be any cold surface on which condensation could form. It also eliminates the problem of thermal bridging which would occur on a cold deck, as the insulation would be between the joists (see video for comparison between warm and cold decks).

The roofing system we used was Resitrix Full Bond, an EPDM covering which was supplied by Laydex. This layer was bonded to the polyisocyanurate rigid foam insulation (PIR) which was mechanically fixed to the deck. PIR is normally used for living roof structures as  it provides much greater thermal efficiency than wool-based insulation, and its rigidity allows the EPDM layer to be bonded to it fully. We were unable to find a suitable ‘natural’ alternative to PIR and had to observe the specifications of the roofing system we opted for.

For our roof, we were required to achieve a U-value of 0.16 W/m²K – to do this we needed a minimum of 150mm insulation. We decided to install 160mm, as retro-fitting insulation to the roof would be almost impossible and the extra depth will help to achieve our overall A3 rating.

The roof insulation arrives!

Insulating the Roof:

Working with Ed Sullivan and his crew, we decided that we would insulate and cover the flatter, more gently sloping parts of the roof first. Then Maria and I would insulate the reciprocal roofs before Ed and his crew returned to complete the bonding of the EPDM covering.

We purchased enough insulation for two layers of 80mm (160mm of insulation) to cover the whole roof. As the insulation is rigid, we needed two layers of 80mm sheets as we were able to ‘bend’ them into the contours of the roof. This would not be possible with 160mm sheets. This did entail a lot of repetitive work as each layer was quite similar but we had to ensure that we bridged the joints in the insulation, where possible, to make the insulation effective. The insulation was affixed to the deck with metal fasteners and was then coated with a primer which was fully bonded to the EPDM cover.

 

Bonding the EPDM to the insulation

PIR insulation affixed to the deck

 

Once the flatter lean-to roof was insulated and covered we began to work on the reciprocal roof. This was towards the end of July and luckily the weather remained mainly dry. It took about two weeks to complete the insulation of the reciprocal roofs as there was a lot of cutting, fixing and offering-up. The day after we finished insulating the roof the summer rains began falling!

Lots and lots of cutting…

Completing the insulation jig-saw puzzle

 

When the insulation was completed, we had a delay due to weather and contractor commitments. However, by mid-September the weather had improved and we were able to complete the EPDM layer…at last.

 

Welding the EPDM layers

Detail of roof light upstand

 

After the roof was waterproofed we were really exhausted and decided to take a short break – our first holiday in several years. A welcome rest.

 

Other jobs:

a) Insulating the Void: The void between the top of our straw bale walls and the underside of the roof was insulated and covered with wood fibre board.

For the insulation we used both hemp lime and wood insulation. We purchased the hemp lime from Marcus at Hempire Ltd. We were aiming to fully insulate with hemp lime, but as it needs to be shuttered into place, it was really difficult and impractical to try to insulate right up to the underside of the roof with it. We decided to insulate the lower part of the void with hemp and complete the rest with wood insulation.

This was quite laborious, about 4 tonnes bucket-by-bucket, working under the roof overhang. Ideally this could be sprayed into the shutters if there is equipment or a contractor available to do it.  

 

A ton bag of hemp lime insulation

Hemp lime insulation in the void

 

b) Installing Wood Fibre Boards

When we finished adding hemp to the void we bought some external and internal Pavatex wood fibre boards (40mm) from Acara Concepts. This product is a very ecologically sound one, as it is made without any bonding chemicals or deleterious practises. It also performs very well as an insulating material, and it allows for breath-ability and acts as a thermal mass.

The external boards are slightly smaller but much more densely packed than the internal ones. The were affixed to the wooden framework we built on top of the bales at 400mm centres. This job involved a lot of cutting as the fibre boards had to be shaped around the roundwood rafters. It was also slow moving as it involved working from a  scaffolding deck.

 

Fixing wood fibre boards internally

Wood fibre boards in place

 

 

 

 

 

 

c) Windows and Doors

Openings in walls are very obvious places where water can ingress, and where heat can escape. For straw bale walls, dampness can lead to rotting straw which has to be replaced if it cannot be dried out, and it is a very difficult problem to correct. This is one of the most important details in our walls.

We began looking at windows and doors after we started building our walls. We visited several showrooms and searched for ideas. In order to satisfy building regulations, our windows need to achieve a U Value of  1.2, and our doors a U Value of 1.4 (or better) – these values could be achieved with double glazing.

Luckily my cousin Joe at Finlay Build is an agent for Camden Windows. As Finlay Build is a local firm Joe was able to spend a good bit of time discussing our requirements and providing us with excellent on-site advice. We decided on triple-glazed UPVC windows and doors which were installed in September, increasing from double to triple glaze added approximately 10% to the total cost, which we decided was worthwhile. This enabled us to achieved an improved U Values of 0.9 for the windows, and 1.2 for the door.

Finlay Build installing windows and board

As well as installing windows we had to decide on our window sills. Wooden sills, whilst appealing, are rarely installed locally. Concrete sills weren’t desirable and would have been too heavy to work into the straw, so this left aluminium sills. We worked out some of the detailing with Joe who installed the windows and then we contacted David Gorry at Gorry Stainless Steel who manufactured our sills.

We found it very useful to use locally based suppliers and manufacturers. One of the lessons we’ve learned on this build is if there is something that you require to be made bespoke, it is vital to be able to speak directly to the person who is making it, particularly when the tolerances are only a few millimetres. This relationship with the suppliers or manufacturers is more easily achieved when dealing with local, small-scale firms.

The windows and sills were installed in a day and a half. The roof was waterproof and we now began preparing for plastering!

d) Preparation for Plastering

The Lime arrives…but…

We thought that we’d have time for plastering before the weather got colder. However some early frosty weather in October meant that we had to cancel plans for plastering this year and complete it in late Spring 2020 (lime plaster needs to avoid temperature below 6ºC or it may crack before drying).

Currently we are working on installing our raised wooden floor and ideally would like to have the floor completed (including the underfloor heating system) before we begin plastering next year.

We do hope to complete our house in 2020. It is impossible, at this stage, to suggest an approximate date as delays and difficulties will always play a part in any building timescale.

We do think it’s realistic to be finished some time next year…

The swallows have kept us company during the summer with their beautiful singing and amazing flying. They nested inside in the roof and have had two clutches. These young chicks are learning to fly. They were untroubled with us working close by and regularly serenaded us singing from the scaffolding. We look forward to their return next summer.

 

This is my favourite photo from 2019. I think it really encapsulates the essence of being a self-builder.

Building the Roof (II)

Summer 2018 was a record-breaking season with the warmest and sunniest weather in over 40 years. Such exceptional weather was ideal for building a 200 sq m roof as we were working under the sky for the entire summer. The overhang (500 mm) adds a lot of extra area to the roof – the overhang being necessary to protect the walls from driving rain. We had already covered a lot of the roof with cladding and now needed to build the roof deck to support the insulation and the living roof.

Part 1: Roof deck

The roof deck involved fixing square timber to round timber, which added a level of complexity and difficulty to the task. The first layer of the deck consisted of 150 mm x 50 mm (6″x 2″) timber laid over, and in opposition to, the roundwood rafters at 400 mm centres, where possible (for greater span we used some 220 mm x 50 mm).

Building the deck on the L-shaped part of the roof (north and east side) was reasonably straightforward as the surfaces were quite even and only slightly sloping. However for the reciprocal roofs, it was a very difficult and time consuming task, as the roof surface is made up of many different planes which needed be connected and covered. The complexity of this task considerably lengthened the time budget for the roof. We once again engaged Osian to help us with the carpentry on the roof and to speed up the process. The roof deck took 16 weeks to complete.

The north-east corner of the roof

Larch cladding on the roof. This is also the internal finish on the ceiling.

 

Each reciprocal roof required over 100 separate and different pieces of OSB to cover it – like solving a big wooden jigsaw puzzle. Each piece had to be individually measured, cut, offered up, altered, glued and nailed.

 

Detail of completed OSB deck on the south side of the roof.

Detail of the 150 mm x 50 mm deck

 

Timber size and strength dictates the span it can be used for (see span tables). An alternative approach for our roof could have been to use larger timber e.g. 225 mm x 50 mm (9″ x 2″) to enable greater spans to be achieved, and would have used slightly less timber. However, the complexity of covering the reciprocal parts of the roof would remain. Another alternative would have been to make up grillages on the ground to cover this part of the roof and use a crane to lift them into place (a more expensive option).

 

Lots and lots of measuring, cutting, nailing, gluing, offering up…at least it was sunny 🙂

View of the east side of the house

 

 

Part 2: Fascia

The purpose of the fascia is to cover and protect the roof’s supporting timbers and insulation. Due to the size of our roof rafters and the deck we built, the height of the fascia in places is almost 1,000 mm. It also follows the contours of the roof, so that it is wavy in appearance.

For most of the roof, the fascia consists of 3 lengths of 225 mm x 20 mm fascia board which is biscuit-jointed, glued, and screwed together. It was then nailed on to the roof. The fascia was built in various sections, which were then fitted together onto the roof. This work took place at the beginning of September. The weather was still good for roofing and we were hoping to complete our roof covering before the weather changed.

 

Fascia following the roofs shape

Osian helping us out to build the fascia

 

Part 3: Vapour Barrier

The purpose of the vapour barrier is to prevent the build up of moisture in the roof’s structure when cold and warm air meet. We contacted Laydex who supply systems for green roofs. The Vapour Barrier we used was Alutrix 600, which is a high performance barrier. Applying this was straightforward, a primer was painted on and then the Alutrix was applied (there are excellent videos to help do this).

Applying primer

Vapour Barrier on roof lean-to

 

The completed roof…

 

Part 4: Roof Lights

During the building of the deck, Osian made four wooden dodecagons (12-sided shaped) which were affixed to the roof openings, once the rafters were cut back and levelled. We recycled some of the Larch we had kept from our framing bed for this.

 

One of the four larch dodecagons for the roof opening

Larch dodecagon in place

 

We purchased two roof lights online and they were relatively easy to install, although this depended on the weather. As it was now November, we had to wait for a calm, dry day to complete the installation.

 

Roof light installed

Roof kerb in place

 

Unfortunately, time and the weather were against completing the roof in 2018. It still needs to be insulated and covered with the waterproof barrier. We were a bit disappointed because ideally the roof should have been water-proof by the end of the year. It may well be that our time scales were over-ambitious as there is a high level of unforeseen complexity to the work, which, as amateurs, we found difficult to factor in.

Towards the end of 2018, we covered the entire roof with 1000-gauge polythene to protect the vapour barrier. We will be aiming to complete the roof in 2019, with perhaps a more realisable timescale.

Natural Building

There are many definitions and interpretations of natural building; it is a collection of different approaches to building rather than a ‘one size fits all’ term. One definition I think which adequately sums up our approach to natural building is “a building philosophy that emphasises sustainability through using minimally processed, locally available, plentiful and renewable resources to create healthy living environments” (Crimmell and Thomson, 2014). I think this is a much clearer definition than ‘green building’ or ‘eco-building’ – this three letter prefix has almost become meaningless when used in relation to the building industry and is often an example of ‘green-washing’.

In our experience when you reduce the embodied energy in your building materials, e.g. straw bales and roundwood you do have to add considerable amount of physical energy to the building process in order to utilise the materials. For example our roundwood had to be debarked and will have to be further cut and jointed to become structurally supportive – all of this takes lots of time and energy and no doubt the finish will be beautiful, but it is definitely not a short cut.

To get most of the bark off we used both debarking spades and a small axe for tricky bits

The debarking of all our poles took four weeks (5/600 hours of labour) and involved brothers, sisters, nieces, nephews, fathers, uncles and friends. We had four debarking spades so that anyone who came could help out.

Luckily the weather in April was really dry so the moisture content in the wood has begun to reduce (some of the poles were over 50% moisture – they need to be below 20% when we close off the house).

It was great working outdoors during this period and we’ve been visited by a cock and hen pheasant, several rabbits, and, a startled hare. The cattle and the swallows have returned – along with other birds – there is a frenzy of nest-building in operation.

When completed we were left with a huge amount of bark which will be used as mulching around our site – for gardening and walkways.

The debarked poles were measured and marked with Roman numerals to aid identification in the construction phase – this task was quite complicated and took about two days to complete – we checked the lengths and diameters against our saw list and plans. The poles were then moved up to the site -we were able to move the small diameter poles (150mm) which will be used in the roof ourselves – but we had to hire machinery to move the larger diameter ones (300-350mm).

Moving the large diameter poles

Unfortunately due to some humid weather mold has begun to grow on the poles, this is a natural occurrence on debarked wood, and we will have to deal with it when the poles are being erected in the timber frame.

The mold spores travel freely through the air and by debarking the poles we have provided an ideal habitat for them! We have experimented with bicarbonate of soda which not only removed the greenish/black mold but also seems to prevent it from returning.

Large diameter poles on site. Next stage – wooden ring beam, frame and roof…

The next stage of our build is to begin work on the wooden ring beam which sits on top of the tyres and will support the straw bale walls. We will be working with a roundwood carpenter to help us with bracing the poles, and are awaiting the delivery of a tripod to aid lifting the large diameter poles.

Marking each pole at both ends is essential. II means diameter 150mm and length 3,500mm (3.5m)

Our timing is quite important and ideally we’d like to have the roof on by the end of July/early August so that we can get the straw walls up and plastered before winter.

Car-tyre foundation

I first came across the idea of using car tyres as a building material watching Garbage Warrior, a documentary about Michael Reynolds and Earthship Biotecture. In Earthships the tyre is rammed with earth and forms the north wall of the building. Here it absorbs the sun’s heat during summer and it slowly releases it during Autumn and Winter. It also recycles or up-cycles waste material.

Levelling off the lowest point of the site.

For our house we are using car-tyre foundations to support our straw bale walls. The tyres are rammed with pea shingle (10mm shingle) and they not only support the walls, but also act as a self draining foundation and a damp proof course at the same time. The metal within the tyre means that it will act like a gabion. And they’re free to collect!  The self draining foundation is vital as it means water will never be able to wick upwards and affect the straw. Straworks have produced a very useful technical drawing of this type of foundation, which we are following.

Keeping the tyres level and more than 200mm from the centre points of the roundwood poles

We will need around 300 for our foundation and they will all have to be levelled and rammed…a considerable task. We have collected over 300 tyres (205s and 195s) –  with ramming each tyre will swell by 20-30mm. On our best date so far we filled 20 but on most days we will average around 14. This is quite heavy work and after two weeks of constant work we rewarded ourselves with a Saturday off.

There was some very difficult weather during this period which saw temperatures as low as -4ºC and included Storm Doris and Ewan. This site has become more muddy and some areas are difficult to manoeuvre in.

However tyre by tyre the foundations are taking place and we’re expecting our roundwood next week so we’re rolling with lots to do. Looking forward to finishing the tyres and starting on the wood.

Reinforcing the lowest point of the site with additional tyres.

It’s worth remembering, when laying out the tyres on the perimeter of your site, to leave enough spaces for air venting the floor (if you are building a raised wooden floor) as it would be a difficult job to retrofit them when your walls are built. Your local building regulations will have a calculation for working out the number and size of the required air vents.

The groundwork begins

January has been a busy month – site preparation and ground work. This initial phase of our build begins to change the character of the site. It becomes noisier, more mechanised; the soil is dug up for foundations and trenches; large lorries arrive and dump tonnes of aggregate; whacker plates; rollers; elephant’s foot etc. In short it begins to look like a building site and includes the following parts;

1: Remove the topsoil – all organic material (top soil) from the house’s footprint was removed. This also means we now have a massive heap of clay (100-150 tonnes) to store somewhere.

Top soil removal

It’s a good idea to consider this carefully, as if it’s stored in the wrong place, it will cause delays later on.

Your JCB driver also needs to separate top from sub soil/gravel so that it can be later added to your garden or used for raised beds.

2: Excavate holes for the poles – each round pole which will support our roof structure needs a cubic meter of structural aggregate (T0) as a footing.

Setting out the location of the poles

23 separate holes were marked out and filled, ramming at intervals to achieve maximum compaction.

3: Add additional layers of aggregate – over the entire footprint an additional layer of 300mm of permeable aggregate (T2 or 804) was added. And lastly 50mm of blinding (T3) was added. All rolled with a vibrating roller.

Another 20 tonnes

All aggregate has to be certified and the receipt must show this for building regulation. Aggregate was from a local supplier (http://www.kilmurrayprecast.ie/).

In total we added 200 tonnes of aggregate onto the site. The weather has remained quite dry which makes large, heavy groundwork much easier to undertake. In fact on one of the recent stormy days dust on the site was a problem – which is almost unheard of in Ireland…in January! What I learned here about project management was the importance of booking the aggregate lorries in advance so that the JCB is working constantly and there is a steady stream of work.

The next part of groundwork to be completed is a plate-load test to get accurate information about the bearing of the soil.

In addition to the groundwork we also erected a fence to mark the sites southern perimeter and lay ducting for our electrical connection and put in piping to move a water trough for the cows (who’ll be returning when the weather get warmer and the grass gets sweeter).

Who needs the gym in January when you can swing a sledgehammer?

We also began some planting for our shelter belt moving some of the small white thorn and black thorn bushes which are beginning to grow on the site because the cows are not there to graze them back.

It makes me realise about how true it is that a forest is the most stable ecosystem and one which land will return to if left untouched.

Harvesting the straw

Harvest time is always the best time to be on a farm. If you’re lucky you’ll enjoy warm summer sun, beautiful sunsets and smell the sweetness of the land on the breeze. Of course summer can also infuriate; the weather can be changeable and often dull (as it was this summer), the harvest could be late and the warm summer sun may be shaded with cloud cover interminably. Harvest always brings the hope that ‘this year’ the weather will hold and that it will be better.

9 August…the field of straw ready for baling.

This year’s harvest was very important to us as we needed to source the straw bales for our house. This was trickier than imagined for several reasons;

1. Type of bale – almost all straw in now roller baled so finding small rectangular ones can be difficult.
2. Transport – you need a tractor and trailer or a lorry.
3. Storage – they need to be stored until next Spring/Summer when they will be used. The storage must be dry…if they get wet, they rot.

The latter two problems had ready solutions – I could use the old milking parlour on my parents farm for storage (we cleared out the old abrest-style milking system) and we could borrow a flat trailer from a local farmer to transport them with the old Massey tractor.

My Dad in the Massey pulling the trailer

For the initial problem we had to do a bit of investigation. Luckily my father is a retired farmer (although farmers will always be farmers) and was able to search the local area for sources of straw, and for a rectangular baler. This was a vital local link. If you have trouble finding bales you’ll need to chat to farmers, they tend to have a really good idea of what’s been grown locally (also check the Farmer’s Journal for straw sales or sites such as donedeal.ie. A local agricultural mechanic may also know who has a rectangular baler).

The farmer agreed to sell us around 500 bales. We arranged another contractor to bale for us. The total cost of this was €450 for the bales and €200 for the contractor. Luckily we were able to transport the bales ourselves as this would have added significant transport and handling costs.

The weather was very unpredictable with rain every other day. This meant that even though the winter barley was cut the straw wasn’t dry enough to bale. We needed two dry days with a bit of a breeze to dry the straw. We waited for over a week for these ideal conditions to take hold. On the day we were due to bale we had to wait for several hours for the dew to evaporate. Eventually we were ready. For this we had lots of help from friends and family.

The baler had to be adjusted to get the correct length and compression of the bales – average length 1.04m, weight 16kg+ (see http://strawworks.co.uk/bale-standard/ ). This took a few rounds of the field to achieve. We bought more bales than we’ll eventually use just to be sure…you can’t have too much straw!

We worked from about midday until  after 10pm to collect in all our straw. We had a core of 7 people, four on the tractor and trailer and three with a car and trailer for most of the day. After the first load, there was a brief hint of rain – a few drop – but luckily, nothing more. It was a huge relief to complete this task. We now had the building blocks to our house, beautiful golden, dry, straw.

A few days afterwards a friend who had helped out with his son told me they had a great day and really enjoyed the experience. I think it was a first for both of them. This is the great thing about the harvest, it is a special occasion. It is something we’ve done since the evolution of farming in the Fertile Cresent 6,000 years ago.

Collective energy and friendship has made our harvest possible.

A real landmark day for us.

A pygmy shrew decided to hitch a ride on one of the loads of straw – interesting little guys. Despite their cuteness, they are one of nature’s foremost predators. They have to consumer 1.25 times their body weight each day due to their very high metabolic rate. They kill up to 250 prey each day to survive…luckily I was wearing gloves!

Building a workshop

After the walls were raised, we were quite elated as the structure began to realise its form. It was soon afterwards that we realised that there was an awful of work still to be done to fully complete it. Despite this, nearing and reaching a state of completion was now closer.

The first task was to complete the roof with planking (12mm). We also added a parapet or upturned fascia (150mm) to contain the living roof. The weather was beautiful again, indeed so warm that my ears were sunburned! One mistake we made here was not measuring the roof area more accurately (diagonal checks) as the finished roof is not completely square but not noticeably so.

We then began work on the walls, this meant choosing the location of doors, windows and air vents. We found a door with a nice office-style window near a skip in town. Two of the main southern windows I bought from http://www.donedeal.ie, the east windows was from a large, old window my parents replaced in their home and we made the rest ourselves. This took  6 days in total working about 6-8 hours a day. The final day was spent making detailed cuts on the lengths of cladding which had to fit around windows, etc. The skills we’ve developed measuring and sawing meant that although a very detailed thinking day, we worked well and made no mistakes. We learned that cladding is excellent at hiding any mistakes and it looks beautiful too.

Next week, work on the living roof and try to finish the floor.

Meanwhile our commencement day is October 28th…we can officially begin building our house.

Nearly there…

Raising the Walls

I remember watching the film, Witness – which had a fairly ridiculous plot – but it did have a great barn raising scene. The whole community came together to achieve the same ends. Putting our Site Office/Indoor Workspace together followed a much more realistic plot and didn’t have the sexual division of labour evident in the Amish community.

We moved the individual posts and flooring joists up to the site and set about assembling the four sides. We put the flooring joists in place, got them all level and braced them the day before. Preparation was essential and double/treble checking, as we made a few mistakes which would have taken up valuable time the following day. Luckily during this time the weather was sunny and dry – perfect for outdoor work. We decided to work seven days a week as any long, sunny, dry spell in October in Ireland must be maximised.

Flooring joists levelled and three of the sides assembled

Working in the Autumn sun

We asked friends and family to help as each section took at least 4 people to lift and hold and a further three people to support.

On the morning we were due to raise the walls the sun was shining beautifully and the sky was almost clear (just like in Witness! – No beards were used in the assembling of this!).

Everything fitted together with a bit of persuasion. It is important to be calm and informed when doing this and a little force is also required. We propped each side when it was level and then braced it. When all four sides were in place we proceeded to install the four roof trusses (200mm x 50mm x 4.6metres). Handing such large pieces of wood involves good team work and communication. These went on with some persuasion and everything was solid, supported and level.

Happiness