Will it fall? Critique my design please

[crappy]

At the risk of being shot down, have I under or over engineered this?

Had various other threads on here about my solar mount - now for the final design. I took all your advice

I am building a "shed" at the back of the garden to keep the lawnmower etc in. On said shed I will be placing 20 solar panels. Below is the frame, heights are to ensure angle (41 degrees) is good for winter and summer.

• Posts 150x150x 3.6m for rear. 1m for fronts.
• Main stringers are 9x2s x 5.4. The posts will be notched and they will rest in that with the joint on the notch.
• Joists are 4x2 x 4.8m. Joists will be notched, seated on stringers and screwed down vertically.
• Gussets will be 150x47
• Upper "ladder" section is only to brace it front-to-back and was going to use 47x150s
• Panels are correct aspect to roof and weigh 18KGs each.
• "roof" was going to be 18mm ply with felt over the top.
• Panels to mount on rails screwed into ply/joists.
• Posts to be seated in steel bolt-downs on concrete foot. 50x50x50cm. I did not want to do a whole slab. Bad?
• I will be - at some point - adding shiplap down the rear for a bit of wind protection.

My main questions are:

• Bad design? Add / remove anything?
• Sizes "mostly" ok?

 

[John D v2.0]

Hope I'm not rehashing any previous advice here...
I feel like your timber sizes are ample, I think the fixings are going to be more important.
Also your diagonals are all side to side where the plywood will provide plenty of racking resistance anyway, but there's not a much front to back. They are also short. Id be tempted to provide a full diagonal the back side, and on the ends also from the back ground level to the bottom of the board. Iassume the steel bolt down brackets won't provide much moment resistance?
Is it in an exposed location or very sheltered? That would make a difference.

 

[scbk]

Don't use ply/felt, it won't last as long as the solar panels

 

[crappy]

Also your diagonals are all side to side where the plywood will provide plenty of racking resistance anyway, but there's not a much front to back.
They are also short. Id be tempted to provide a full diagonal the back side, and on the ends also from the back ground level to the bottom of the board. Iassume the steel bolt down brackets won't provide much moment resistance?

Yes, this is why I put the upper "ladder" thing in to try form that triangle. I can't go much lower because I would not fit the tractor in (really, I inherited a 1959 tractor I am restoring ) It's currently at 2.4 above ground, I could drop it by 400 but don't think that would make much difference?
I could double up on the short posts as they're relatively cheap.

Is it in an exposed location or very sheltered? That would make a difference.

It's actually very sheltered. My garden is a V shape in it's in the narrowest part I can fit it into. There is a hedge sheltering it on the rear and side which is currently around 2m. I don't mind growing it more. Behind that is a huge farmer's field so quite exposed but for the hedge.

Don't use ply/felt, it won't last as long as the solar panels

What other option should I try? Given the panels will protect it a lot I thought I might be able to get the span out of it but admittedly, am nervous.

 

[RonnyRaygun]

The biggest issue I see is that you’ve got very little to resist the wind loads that are going to hit the solar panels from the front / back.

You’ve basically got a big sail that will catch a lot of wind and you will be completely relying on the upright timbers resisting the wind load.

Put in some cross bracing to resist the wind load. You could do it either in timber or flat steel plate (might be easier).

Same at the back - put in some diagonal cross bracing to resist racking. The forces will be lower in this direction but still significant.

 

[lostinthelight]

Will there be a gap between panels and roof ,your pics don't show that. if not panels may get too hot and output decreases . If you had a more reflective roof covering and good gap you could use bifacial panels for a greater output.

 

[crappy]

Same at the back - put in some diagonal cross bracing to resist racking. The forces will be lower in this direction but still significant.

You're right. I can easily put the diagonals across the back. Will add.

I will be adding shiplap down the back as a wall. This will minimise the upward / catching force of the wind but still not ideal. It'll just be a sideways loading.

 

[crappy]

Will there be a gap between panels and roof ,your pics don't show that. if not panels may get too hot and output decreases . If you had a more reflective roof covering and good gap you could use bifacial panels for a greater output.

Yes, the picture does not show. The panels will be mounted on a rail and allow airflow under.
Not seen bifacial panels before. Pretty cool. Unfortunately I've already orded mine

 

[Jake2021]

Hi
I’ve been thinking about this a
Lot! Your design imo is nearly there

in relation to your posts I have been thinking if you get some heavy duty steel box section 3-3 1/2 fit in length and 6x6 in size dig a hole 2 ft place the box section in the hole and concrete it in which would leave you 1 1/2 foot above ground , shave the slightest bit off your post and pop it inside the box section with two high tensile bolt passing through the box section and post this would be pretty sturdy in design yet it would allow
You to remove them
If needed whilst keeping them
Out of the ground

more your design I think you need to look at a little more support on the back and sides to stop it twisting , I’m pants at drawing but hope this makes
Sense

 

[Jake2021]

I’d also look at using joist hangers wherever you can
Best wishes
Jake

 

[^woody^]

It's a crap design for a shed. The stuff wil get wet.

 

[Jake2021]

Lol … good job it’s for his solar panels and tractor lol

 

[Lower]

Why do you need the ply surface? Why not just pitch your stringers at the right spacing to allow the panels to attach to them directly? Then you can leave gaps between the panels to reduce the sail effect and reduce the amount of wood that water will collect on.

 

[freddiemercurystwin]

Because apparently it's a shed with no sides. I just checked my shed and turns out it has sides and the stuff inside is dry. Perhaps my shed isn't a shed?

 

[JohnD]

If you felt like it, you could design a single structure that was an enclosed shed with a large sloping roof having solar panels mounted on it.