A shed roof is certified to carry itself, the cladding and the wind. Nothing else. Here is why we design for a lined ceiling and 600kg of solar before you ask for either, and what that means when you compare our number to a shed quote.
Category: Construction & Build Author: Brian Best Reading time: Approx. 4 minutes
Every so often someone rings and asks why our building is dearer than a shed quote they have in front of them. It is a fair question and it deserves a straight answer, so here it is.
A shed roof is certified to carry three things. Itself, the cladding, and the wind. That is the job. It is a good, honest structure and it does that job for decades.
The trouble starts the day you want the roof to do anything else.
Plasterboard
If you line a ceiling, the roof structure stops being a roof and becomes something a brittle sheet is screwed to.
Engineers work to a deflection limit, which is how much a beam or a purlin is allowed to move under load, written as a fraction of the span. A shed is typically around L/150. Over a six metre span that is about 40mm of movement. Nothing in a shed cares about 40mm.
Plasterboard cares. On our buildings I work to about 10mm over that span, four times tighter than the shed number, because that is what a lined ceiling needs to stay looking like a ceiling instead of a map of cracks. That stiffness is not a finishing decision. It is heavier sections, more portals or closer spacings, decided before a single sheet is rolled.
Solar
This is the one nobody asks about, and it is the one that has changed the most in the last ten years.
An average panel weighs about 20kg. A typical installation is thirty of them. That is 600kg sitting permanently on a roof, and the drawings for a cheap shed never had it in them. Then add the racking, the brackets and the cabling. Then add a couple of blokes and their tools walking around up there on install day, and again every time the panels get cleaned, or one gets replaced, or the system gets upgraded.
It is worse than the raw number suggests for two reasons. It is permanent, unlike wind, which comes and goes. And it is not spread evenly. It lands in rows on the purlins and the fixings, which is exactly where a shed is leanest.
Almost everyone puts solar on eventually. So we assume you will, and we build a roof that can take it, whether you order panels with the building or bolt them on in five years.
The word is trafficable
There is a term for this and it is worth knowing before you buy anything. A trafficable roof is one designed to be walked on. Many 10A sheds do not have one. Not a weak one, not a marginal one, simply not designed for it at all, let alone designed to carry solar on top of the person installing it.
That matters because for the next forty years that roof gets used. Gutters cleaned. An antenna or a dish. Air conditioning. A leak chased after a storm. A solar upgrade when the inverter dies. Someone will be up there, and they should not have to wonder whether the building minds. We design for that, up front.
Why we do it at the start, not later
Because adding capacity to a frame that is already standing is the expensive way around, and sometimes it simply cannot be done.
On paper, at the design stage, stiffening a roof is a line in an engineer’s calculations and a difference in the order. On a building that is already up and clad, it is an inspection, a re engineering exercise, new members threaded into a finished structure, and a bill with no guaranteed outcome at the end of it. That is why we would rather spend the money in the drawings than have you spend three times as much undoing it.
What that means when you compare two quotes
When you put our number beside a shed number, you are not comparing the same building. You are comparing a structure certified to hold itself up with a structure certified to be lived in, lined, loaded with solar, climbed on and signed off as a home.
That difference is not in the brochure photos. It is in the engineering, and it only shows up later, when one of those buildings can do what you asked of it and the other one cannot.
A cheap shed is exactly that. You always get what you pay for.
If you want to see what a building engineered that way costs, our prices are published: shed house plans and prices. To lay out your own and see it in 3D, start your design. And if you already own a shed and you are wondering whether it can become a home, read this one first.
Brian Best
Founder & Builder
Shed Homes · Class 1A Kit Homes · Australia-Wide Delivery sales@shed-homes.com.au · 07 2112 3095 · shed-homes.com.au
