The roof
The roof is constructed as per the installation guide, it starts off with the front and
back gable sections being bolted together and then bolted with the aluminium roof and side beams. Gable
braces which strengthen the gables and act as rain drips are screwed on to the front faces of the gables.
It is best that this is done on a flat surface and not an undulating lawn as below! One of the problems I
faced later is that unless this is all square, the roof panels screw holes won't line up. This caused me a
little grief when the final panels were fitted. Learn from my mistake and make this section on a patio or
garage floor if you can!
The roof framework
The roof panels are screwed to the top and middle roof beams and bottom side beams. Don't
forget to use one or two security screws per panel. Aligning all these holes is very fiddly and
frustrating. It needs two people. I advice not to use a power driver for this, the screws will easily
strip the holes and you can't afford to make mistakes here.
Laying the roof panels
The centre of the roof has roof ridge covers screwed to it. There is a gap under which the
rain could get and down inside the shed. This is quite possible with the gales we get here, so I sealed it
before placing the ridge covers on with ordinary flashing tape. However, this will seal up an important
ventilation gap, especially on warm days when the hot air inside the shed would normally vent out through
the top of the roof. I had to weigh the pros and cons of this and decided to seal. It depends on the sort
of weather you have.
Sealing the roof ridge
Once the roof was complete it was mounted on boxes so that I could crawl underneath. It was
now necessary to fit the roof to a wooden frame, similar to that at the top of the shed walls. The roof is
far too flexible without this and you wouldn't have any means of attaching the wheels for it to run on.
The frame was made using the same 47mm x 75mm timber as the shed frame, with the 47mm edge
screwed to the roof. Holes are already drilled in the roof beams and gables and 1.25"x8 and
0.75"x8 stainless steel panhead self-tappers (Screwfix 2573 and 4452) were used to screw the roof to
the frame. You will probably need to drill pilot holes beforehand. In the picture below you can see the
green painted frame fitted to the roof. The unpainted length of wood on the right is just for support
during construction.
Under the roof building the wooden support frame
The gable sections extend below the side beams although the holes are all on the same
level. As can be seen below, the wood frame extends down below the side beam but is only a little lower
than the bottom of the gable (on the left). The flimsy aluminium side beams also have a tendency to curve
upwards in the middle so make sure that someone places some weight on the middle of the sides when
securing the wood so that it is all level. If you don't the roof will pull the wood up with it and the
middle of the sides will be higher than the ends, which will mean that any wheel located here won't touch
the rails, but be suspended in the air when the roof is mounted on the shed.
When all four pieces of wood are screwed to the roof and to each other at the corners, I
strengthened the corners using 100mm angle braces (Screwfix 4177) on the outside and inside.
Roof detail front corner showing frame and wheels
I was very worried about the strength and rigidity of the roof so I fitted some wooden
corner diagonals screwed into the frame using long TurboGold screws and secured underneath with 75mm angle
plates (Screwfix 3496). Underneath each corner and across the joint between the two pieces of wood I used
a 100mm mending plate (Screwfix 6050). You can see all this in the image below. You're now probably
thinking I'm over the top or mad. OK, granted, but I feel happier about it and the whole roof is solid and
rigid now. Better to be safe than sorry?
A note for those playing close attention :-) In the two images above and below, the front
of the shed is to the left (above) and to the right (below). You are looking at the same front right
corner of the observatory. You may remember on page 7 that I said that the front of the shed does not have
a frame member. The frame member seen across the front of the shed in these images is not screwed in place
and will not be. It is just sitting on the corner posts and placed here to give a little rigidity to the
front whilst constructing. I was going to fix it but decided it was unnecessary after I'd added the
weather boards (it would in fact prevent access to door tracks behind.)
Roof frame front corner detail
Take your time here and think about it all before proceeding. I found building the roof and
frame the most difficult part of the whole endeavour. It wasn't helped by not having it all square to
start with and with only two of us, it was very difficult handling the heavy roof and getting it and the
frame all aligned and fitted.
Next comes the wheels. Don't use castors that rotate. They won't and will lock up when you
try to pull the roof back for the first time! You need wheels. I used eight 50mm rubber tyres fixed
castors (Screwfix 4732). I thought the rubber tyres might make them quieter and smoother than the
nylon-wheeled castors. With four fitted to each side the trick is to make sure that they are all in
alignment, not necessarily with each other, but they must all point in the same direction along a line
between the front and back. If one or two point slightly off then the roof will want to follow them and
end up running off the rails. A slight misalignment will inevitably happen especially as the wood won't be
perfectly straight, so the roof will run off centre a little and not quite return to the same spot every
time. There is a fix for it as I will show on the next page but
do try to get them pointing as straight as possible. I 'drew' a line using a taught piece of chalked
string between two points either end of the side frame member. By pulling it down slightly and letting go,
it flicks the chalk on the wood and the wheels can be aligned to this line. Again, take time and care
here.
The roof complete
You may want to think about other means of rolling the roof. You could try wheels like
train wheels sitting on metal rails mounted on the wooden rails. If you can find some. Or wheels with a
groove cut into them (perhaps you could find some where the tyre can be removed leaving something akin to
a bicycle or car wheel) which move along a correspondingly shaped rail. Sash pulleys might also work. I
couldn't find anything suitable, especially with regards the rails and so left my wheels to just run on
the surface of the wooden rails unguided. As you will see later, this didn't work, hence my fix mentioned
above.
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