Saturday, 21 June 2014

Roof Carpentry

Monday 16th June. Weather: cool, breezy,

After a few days break, the next job was to get the permanent roof on. My lovely volunteers have all gone home and I am working by myself again. We are stuck in a cold, wet airstream whilst the rest of the country is having summer, so it's all a bit of a change from the last 3 weeks.

I have added the rafter bearer in the pic above - the piece of 4 x 2 timber on top of the wall plate. It has taken about three days! 

I had a bit of a problem after the compression of the walls last week. The compression was uneven, and the wall plate was not level: the front wall had a concave dip in the middle of about 30mm, and the back wall was convex by about 20mm. To get the rafter bearers level, I have carefully sculpted them (with a power saw) to reduce their thickness at the ends of the front wall and in the middle of the back wall. It has also taken a lot of time to measure out exactly where to fix them so that the span is constant and the rafter spacing is regular and symmetrical.

The weather hasn't helped. I need to take the covers off to work, but put them back on again when it rains, which was a few times a day for a while. And it's been windy, and loose covers flap around.

Thursday 19th June. Weather improving, some sun, less rain

But by Thursday the weather was brightening up, and I was ready to make some rafters. I had made myself an additional problem by misjudging the height of the temporary roof. The front was too low, and in the way of the rafters. I have raised the whole front of the temp roof by propping it up on the wall plate..................

....................which means that the front line of columns (including my tool station)....................

..................can now go.

Columns dismantled. I am using the 4 x 4 columns on the rear wall plate to get a slight rise to the roof.

This is a first: using my rafter square to mark out rafters! Clever tool! I used to think it was just a set square with a ruler on each arm. I have a rise of 250mm over a rafter run of 4.3 metres, which gives a pitch of 1:17, or about 3.5 degrees.

First rafter takes shape................

.................and seems to be a good fit. Only 23 more to make. Each rafter weighs about 30 kg, so they are difficult to move and work on solo, especially hoiking them up onto the walls.

Saturday 21st June. Weather: warm, dry and sunny. Working solo

Gang-cutting notches in rafters. I'm loving working in my new workshop already. 

Tuesday 24th & Wednesday 25th June. Mainly fine but with occasional showers.

However occasional, showers are difficult to work around. It's currently taking around 20 minutes to uncover the roof, and around 40 minutes to cover it up securely again. I have been just peeling back a corner here and there to start constructing the permanent roof

Rafters at eaves with noggins for stability. I have bought 26 pieces of 200x47mm timber 6 metres long.  I had planned the rafter length to be 5650mm, but I realised that if I reduced this by a smidge to 5640mm, then instead of having a pile of useless offcuts about 348mm long, I could have 26 very usable offcuts 358mm in length, and make some 353mm noggins out of them

Over-lookouts at eaves. This may not be the English name for them; I've been reading an American carpentry manual. The end rafter is overhanging the side of the building and needs quite a lot of support. Lookouts transfer the weight of the rafter and the roof above to the four rafters next to it. Over-lookouts hang on the neighbours and give cantilever support to the eaves rafter; I have made five at each end of the roof. There will also be three under-lookouts that give the eaves rafter some support from below, sitting on the wallplate. These will transfer some of the weight of the roof to the short walls rather than have the whole roof supported on the two long walls.

And the first pieces of roof decking go on at the corners. The decking is sitting on the permanent roof frame, anything above this level is the temporary roof.

Thursday 26th June. Weather - we're on a promise of an entirely dry day.

I've had a couple of dry days in the last fortnight, but these have been days when occasional showers have been forecast but not materialised. Today the met office is saying "No rain. Definitely." It's going to be a long day's work!

9.15 Covers off:

10.15: Temporary roof dismantled: 

My first view of the finished building side elevation..........

....................and of the interior without pillars.

Pile of wood for recycling. 

Actually, I've already taken most of the 4x4 or 100x100mm pillars in this photo. They are going to be used to complete the roof riser on the back wall, shown below

13.00. Riser wall completed. I have left a small opening in the middle of the riser which will become a ventilator

14.00. Five rafters to still to do.

A clearer view of the over-lookouts:

Pile of noggins. As well as the 8x2 offcuts, I have also sawn up most of the 6x2 timber that I used as rafters in my temporary roof.

16.20. Quite a lot of noggins in place. It's a long job. I think I might need some more - perhaps five for each rafter interval.

17.45. So- what's this a picture of?
Is it a bird? ..................................No!
Is it a plane? ................................No!

Hang on. Actually, it is a plane of sorts. In the absence of any lifting machinery (or superman), I have resorted to using an inclined plane to get my sheets of 18mm OSB up on the roof. I think the Egyptians used this technique to lift their heavy stuff.

I know a sheet of OSB isn't in the same league as the stones in the pyramids, but then I don't have a gang of slaves to help me. It was a bit tricky getting a photo of what was going on here, as I couldn't lift and photograph at the same time. I put a ratchet strap around the sheets, one by one; tied a rope to the strap; stood on the roof with the end of the rope and hauled them the inclined plane, which was made from the last five rafters.

(Note on the pictures above. I've shown these to a couple of people, and they have mentioned the "big roller" on the scaffolding, so thought I'd better tell you what it is. It's not a roller for the inclined plane - it's my pond liner, which I am going to use to waterproof the roof.  It weighs about 60Kg! It arrived a few weeks ago when I had lots of help here, so instead of leaving it in the store for me to try and manhandle up onto the roof by myself later, I got my POOSHers to help lift it up to roof height ready to unroll on the deck when it's ready.)

20.45. (Good job it's midsummer.) Nearly all the sheets in place. They're not screwed down yet, and there is still work to do beneath: under-lookouts, noggins etc. That will have to wait for the next dry day

21.45 Covers back in place. Time for a drink!

Monday 30th June. Working solo, weather dry.

This is the third week of roof carpentry and the sixth week since we started working with straw. Unusually, and thankfully, we have a dry forecast for the week. You will remember that last week, I hurriedly got the roof deck into place and covered up, but left quite a lot of work unfinished in the the structure below.

I nailed a few more noggins into place, three per rafter gap making 63 in total. However, the rafters are nearly 6 metres long, and I was concerned that there was still potential for twisting  at the eaves. I had used all my 6 inch and 8 inch timber, but still had a lot of 3 x 2 inch timber left from the temporary roof, so I decided to add diagonal cross-bracing to the rafters instead of noggins.

After a bit of trial and error, and a lot of measuring and re-measuring, I got my chop saw set up to cut the struts shown below, and then cut 84 of them.

A pair for each rafter gap where they cross the walls

Using a brick line to get the roof deck sheets accurately lined up.

Last week when I got the roof deck sheets in place for the first time, I realised how dark the workshop was going to be. I had been putting off a decision on a skylight, but quite quickly came to the view that one was needed. 

Forming an opening with joist hangers. With a possible skylight in mind, I have bought and made an extra two rafters, and I am using these now to double up the rafters either side of the skylight.

 Completed skylight opening 750mm x 750mm, from above.......

......and with a matching "trap-door" cut out of the deck sheet.
(I have battened round the opening and replaced the trap-door for now, until I have a skylight to fit.)

Let there be light! The skylight opening from below.These jobs have taken 3 days, and it's now Wednesday evening.

Thursday 3rd July. Working solo, weather sunny, dry and hot. 

My photo shows a 50mm x 18mm roofing batten, recycled from the temporary roof, which I have cut in half lengthways. I thought this might be a job for my table saw, but it was making heavy work of it. The circular saw was difficult to cut accurately with, and I ended up cutting around 16 metres of batten with a jig saw. The roofing battens are the only timber in my building that has been pressure treated. It's hard to find untreated timber in this size.

I am using these timber sections to make a drip-strip around the entire edge of the roof deck. The picture above is a close up of one corner of the roof deck with the drip strip attached in on direction; the picture below shows how the waterproof membrane will wrap around the drip strip. The idea is that water will run off the roof, down the membrane to its lowest point, then drip off without getting any on the roof timber wet.

I have also screwed down all remaining deck sheets today. There are 20 sheets,  and 28 screws per sheet.

Friday 4th July. Working solo, weather dry, sunny & hot

The carpentry is complete, time to get the waterproof edpm membrane. This is the heavy roll that has been sitting on a high scaffolding hand rail for a few weeks.

But first, it's a layer of geotextile backing. This is to protect the edpm from any sharp projections on the roof. The fibres catch on the SmartPly, making it difficult to slide to adjust it's position once on the roof. I have been using a tarp to unroll and position it, then whipping the tarp out and brushing it flat.

 Geotextile layer complete.

 Makeshift ramp under the edpm roll

Successfully lowered and rolled onto the roof.

First attempt - following instructions on the supplier website - turned out to be the wrong way to do it.

Second attempt was a better fit: 6 metres of concertina fold edpm laid down the centre of the roof.

And here's the roof fully covered and waterproof.. No more worrying about whether the tarps will hold out and keep the straw dry!

I had originally thought that I might leave the roof like this. But: the sunshine was intense today, and the black edpm was so hot that you couldn't touch it. I thought it better to unroll the white tarp on top of the edpm to reflect some heat. It was also helpful to tie down and secure the edpm against wind.

This is the end of the "Roof Carpentry" section. This is also the end of the "weekly diary" entries here; from this point on, work will be a little more intermittent and my posts will also be less regular.

Work remaining on the roof is: buy and fit a skylight; cut the edpm and make a skylight flashing. Secure the edpm around the edges. Make an upstanding roof edge all round. add around 6 cubic metres of lightweight substrate and add plants.Fit guttering and downspout to front side. Work remaining on the building is: doors, windows, internal and external plastering and electrics.

Monday, 9 June 2014

Wall Plate

Day 1: Monday. POOSHers =2 , Weather hot and sunny with possibility of thunder showers

We haven't quite finished wall-raising, but we have started on the wall plate and this week is going to be mostly about this phase of the build. The wall plate is a ring beam that sits on top of the final course of straw.


And we spent a small part of the day on the wall plate. We glued and screwed the outer beams to the OSB bases. The wall plate is going to be in six sections, and each section is likely to be so heavy and awkward that it will take three of us to carry it. .

When we had it laid out on the ground on Friday, we marked up the exact location of each piece. So today, we were glueing one side of the beams, locating them on the OSB and clamping them, and then turning the assembly over and drilling then screwing through the OSB to pull the glued surfaces into tight contact.

 Six wall plate sections laid out. I have positioned the inner beams, and marked them up for fixing tomorrow.

But most of today was spent completing the fourth course of bales. These have been in place since Wednesday,  but before starting the fifth course we have checked and adjusted the position of all bales for alignment then driven 1350mm hazel stakes (two per bale) down through all four courses. It's been a day's work. You can't see the difference in the photographs, but I hope it will make a significant difference to the evenness of the walls at the finish.

Day 2. POOSHers = 3, Weather warm, dry and sunny.

We laid the fifth and final course of bales in a couple of hours this morning. It was the most straight-forward course of the five: no stakes to use, no window openings so fewer bales to customise. Better still, one of the part-bales we made last week was the perfect length to complete a wall section today.

 Not so much headroom on top of the wall

 Fifth course complete

Back to the wall plate this afternoon. We have been gluing and screwing the inner beams and noggins (spacers) to make it as strong and rigid as possible. 

If you look very closely at the mid-line of the OSB, you can see that we have also drilled 25mm holes here and there. These are for the final hazel stakes that will be driven down through the wall plate into the top courses of straw.

The wall platee - six finished sections back in the store and ready to put on top of the walls tomorrow.

Day 3. Wednesday. POOSHers = 3, Weather warm & dry

It's time to fit the wall plate, and the forecast is for dry weather. So - covers off...........

.......................sections up the scaffolding..........................

Position very carefully directly above the baseplate. Plumb lines, spirit levels, tape measures............

..................then drive in the small hazel stakes, through holes in the bottom boards.


Whoops! No photo of the lovely sheeps wool insulation . All voids were filled with 100mm thickness, then the wall plate top covers glued and screwed (or ring-nailed) into place.

Ready for compression tomorrow. 

and I'm hoping that when the straw either side of the window is compressed, the gap between the top course and the wall plate, over the window, will disappear.

Day 4 Thursday. POOSHers = 3, weather : warm, dry and sunny.

We have pre-compressed the straw today. We have worked our way around the walls with four steel bars and four heavy duty ratchet straps. If you look at the photos in "Wall-raising, Week1", you can see some lengths of blue water pipe running across the stem wall at regular intervals. These were marking some slots I had cut across the stem wall ready for this job. We push out the pipe with the steel rods - 20mm steel rebar cut to 600mm lengths - and pass the ratchet straps from one end of the bar up and over the wall plate then down to the other end. When you tighten the ratchet straps, you compress the straw wall between the base plate below and the wall plate above.

Before moving the straps along the wall one at a time, a length of (white) polyester pallet strap goes over the wall plate and under the base plate, tightened up with a monster parcel strapping tool (hired), and this strap is left in place, permanently. It will be plastered over.

Pictures follow, not necessarily in sequential order:

So: this last photo shows what we have achieved today. We have reduced the height of the walls by around 5 cm! The top of the wall plate was level with the black line on the post before we started.

But, by compressing the walls there has been a much more significant change in the strength and stability of the walls. They feel sturdy and steady enough to build a roof on. However, everyone has been working hard for four days, and we have reached a suitable point to take a break, so today was the last day of work this week.