Sorting out your garage framing from your cladding from your OSB can be tricky. You may not have considered the various types of wood used to build a timber garage until you decided to buy one.
But knowledge is power, and the more you understand about any building you look at, the better equipped you will be to make the best buying decisions. By the end of this post, you’ll understand the difference between a bog-standard garage and a great garage.
What is framing?
The wood in your garage starts with a frame. The frame of the building acts like its bones. The stronger the garage framing, the stronger the garage. That’s why we use C24-graded framing for all our buildings.
What is C24-graded framing?
The C in C24 stands for “conifer” and refers to the type of trees used to produce this timber. Conifers include pine, spruce, yew, Douglas fir, larch and any other tree or shrub that produces cones.
Now you most likely know how much time and attention we pay around here to the provenance and species of trees that produce timber. Redwood vs whitewood is one of the key questions to ask when you’re buying any sort of timber building. But when it comes to framing, we’re asking a different set of questions.
Because most timber merchants couldn’t tell you what conifer species their C24 timber comes from. The species isn’t the important factor. The grading is what’s crucial here.
Grading uses a set of standards to determine the strength of timber. While the species of timber is vital when you want to prevent water ingress, for graded timber it’s all about the load-bearing capacity.
C24 means timber from conifer trees that can withstand 24N/mm2. Since you weren’t expecting a science lesson, all this means is that C24 timber is seriously strong. Builders use C24 timber for floor joists, rafters and wall framing. It’s what you’d find in a new-build house, and it’s what we use for all our buildings, including our garages.
If you’re buying a garage from another manufacturer or supplier make sure to ask about the grading. C16 is conifer timber that can withstand 16N/mm2, so it isn’t as strong as C24 and its grading standards have more tolerance for defects and flaws.
If the timber isn’t graded, you don’t have any way of telling how strong the framing will be, and your garage may not be sturdy enough to last.
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How thick should garage framing be?
AT LEAST 70mm x 45mm.
Garages are large buildings, and the weight of the timber cladding and roofing materials is significant. Your framing holds all of that weight up, so it needs to be solid. Our garages use a minimum of 95mm x 45mm framing. Depending on the size and design of the building, we may use thicker framing, but never less than this.
What is cladding?
Next up is cladding. If you’re looking at a single-skinned garage, AKA a big shed, framing, and cladding are all the wood you’re getting.
Cladding is the outer layer of your garage. You might think that cladding only comes in two varieties – vertical and horizontal – but there are tons more options than this. Different profiles, timber types and finishes mean that you can choose a timber garage that fits your aesthetic perfectly.
Our garages use either horizontal weatherboard cladding or vertical close board and strap cladding. But the world of garage cladding options is so wide that we have an entire blog post dedicated to it.
Remember – in a single-skinned garage the cladding you see on the outside of the building is the same that you see on the inside of the building. It’s the only thing keeping the weather out of your building.
How thick should cladding be?
This is not as simple a question as it may seem.
First of all, you must ask how waterproof you need your garage to be. If you’re using the building for storage and it’s not imperative that the contents stay absolutely dry, a single-skinned building might suit you just fine.
If you want a good-quality single-skinned garage, the cladding should be no thinner than 16mm. This is an absolute minimum, and a garage with 16mm cladding is never going to be a particularly solid building.
Anything less than 16mm – forget about it. 19mm-22mm is a better range to consider for a single-skinned building.
You will find, however, that many timber garages use even thicker cladding – 44mm tongue and groove is fairly easy to find. But does thicker cladding mean a better garage?
As with so many questions relating to this topic, the answer is, “sort of.”
Because once you’re shelling out for cladding that’s thicker than around 22mm, you’d be better off spending your money on a garage that will actually stay watertight.
Remember the golden rule: a single-skinned garage will stay mainly waterproof. And yes, this rule also applies to interlocking log cabin garages. It doesn’t matter how thick that single skin is – one layer of timber does not equal a watertight structure.
For a watertight garage, it needs layers. Like onions. And ogres.
Rather than paying extra for thicker cladding that won’t solve water ingress problems, stick to the 19mm-22mm window and accept the limitations of a single-skinned garage.
Or, come and see us at Gillies & Mackay and we’ll tell you all about our very clever Garage specification. We guarantee all our buildings for 30 years and our Garages are completely watertight.
What is pressure-treated cladding?
Pressure-treated wood has been treated (under pressure, no less) with a chemical solution that protects the wood from rot and insect damage. Pressure treatment is often touted as making timber waterproof, but this situation is not as straightforward as it seems.
If you’re building a timber structure like a deck or a jetty that’s going to be exposed to water regularly, pressure treatment is a great idea. But if you’re building an enclosed structure with an inside that you want to keep dry, pressure treatment alone won’t achieve this.
While the treatment protects the wood from rotting, it makes it more permeable to water. If you have a single-skinned building with pressure-treated cladding, it’s extremely likely that it will experience water ingress through those walls.
The walls themselves won’t suffer from this, but anything inside the building is susceptible to mould and water damage.
If your garage has more than one layer, pressure treatment is ideal for protecting the outer cladding of the building. But if you have only one layer, pressure treatment isn’t the magic bullet it appears to be.
What is OSB?
Much like pressure treatment, using OSB in a garage comes with conditions.
Oriented strand board, or OSB for short, combines processed wood fibres with glue to make a sturdy, affordable building material. The key thing to remember about OSB is that it must not come into contact with water. When wood fibres are broken up and processed, they become extremely absorbent – remember that this is how paper is made. OSB soaks up water like nobody’s business. Because the layers of wood fibre overlap and crisscross, drying it out is almost impossible. Wet OSB swells, deforms, and becomes mouldy better than almost any other material.
Because of this, OSB is not suitable for use in a single-skinned building – not as flooring, not as roofing, and certainly not as walls. Cheap buildings with OSB roofs and roofing felt are asking for trouble, but this combination is extremely common.
But when OSB is dry it excels as a structural material. We use it as the inside layer of our Garages because it’s well-protected from moisture by the outer cladding, the air gap and the breather membrane that stand between the OSB and the outside world.
With careful design, the excellent properties of OSB – strength, insulation, and durability – really enhance a garage. But as a cheap substitute for better timber, it’s a liability.
If you’re looking at a garage that uses OSB, there’s one key question to ask: “How well is this material protected from moisture?” If there’s any chance at all that OSB will get wet, steer clear.
A Guide To The Wood In Your Garage
So what have we learned? Whatever type of timber garage you choose, you can now check the quality of the framing, cladding and OSB.
If you’re buying a single-skinned garage, check out our Single Skinned Garage Buyer’s Checklist. It has even more information on how to sort the grotty garages from the great.
Or to see our watertight 3-Tier Garages in real life, come on down to our Show Area here in Errol. You can impress us with your framing, cladding and OSB knowledge and ask us all about these gorgeous buildings.
