Progress?

It has been very quiet around here….too quiet (just to roll out that Dead Horse Trope). Unfortunately, unlike the movies, I have no idea if things will suddenly burst into action or not.

I’ve been getting quotes, checking them twice, working out who’s naughty and who’s nice.
Been comparing shed manufacturing companies, and my local retail franchises, and there are big differences in some areas (such as attitudes, willingness to work through designs etc), and very little in others (such as available design options, and cost). I’m not mentioning company names here- this isn’t a name and shame.

I took one design back yesterday to one company, and wanted to see how much cheaper it would be to not do an American barn, with all the doors I originally planned, and go with an Aussie Barn- much lower design, no mezzanine, minimal doors and the price barely changed- about $1000 cheaper.

So this says to me that the decrease in height of 1/2 a metre across a 9 metre length of shed, (total about 12 m2) including all the support beams that decrease, and all the insulation, less 9m in guttering, the cost of a 10 m2 mezzanine, less 3 personal access doors and 2 windows, all added together is only $1000. The erecting cost was unchanged. Wow. Perhaps I should take the American barn, and add an additional 1/2 m in height, more mezzanine, more access doors etc etc. Would the price go up only another $1000? And no difference in erecting cost?

When I queried the lack of difference in price, the response was “I’m only quoting what the software tells me”

I was looking at decreasing the design to minimise cost- I thought I would make a lot of compromises to see how much difference it would make. Very disappointing.

So I then looked at what I could get if my total project budget was capped at $10k. With me erecting the shed, and without even factoring in the cost of lighting, I could not replace what I previously had (which we know was becoming unworkable). You don’t know what you had until it is gone.

I am finding it very difficult to find things to write about, as you would have noticed in the decrease in output. And all this back and forth is very draining. However, without a shed for Stu, there is no Stu’s Shed. And that is not an option I enjoy contemplating. It is a very frustrating situation.

Flat Pack Shed Construction & Design Weakness

There are a few different construction methods used by different manufactures. A couple of common ones are a metal tag/clip system, and tek screws. The first is a very fast method of construction – you can get most of the joints assembled with a quick tap with a wooden mallet. There are then often some metal cross bracings used that utilise a few tek screws to hold it all together.  There is often very little actual framing used, as the shed relies on the panels themselves to not only provide the cladding, but also be the framing as well as providing sufficient stiffness to the structure.

The other method relies on a solid frame structure (normally steel) which then has the panels attached. The cost of this sort of design is significantly higher, but then so is the strength of the resulting structure.

There are a couple of standards that the shed is constructed to, based on the actual location (Vic, NSW, Queensland etc) and the likelihood of severe storms.  The standard for Victoria doesn’t require a cyclone rating, and despite the extra cost, there is surprisingly little that is added to the shed design to get the extra rating.

From experience however, the larger sheds are really tested even in Victoria with the wind strength and speeds that are experienced with today’s weather patterns.  Despite manufacturer claims, some extra bracing is not just a good idea, but I’d suggest mandatory given the weakness of some designs. The clip-together designs have an inherent weakness that if a panel is torn off by the wind, the whole shed’s integrity is compromised, and likely to also succumb.

The point of greatest weakness is the upper corner of the door(s), with the wind gusting over the roof attempting to lift it, it is these corners that often will start detaching themselves first.  Knowing this however means we know where to add some extra reinforcing, which can be as simple as some extra strapping. The other issue can be the tek screws themselves when they are relied on to hold the whole unit together. Some of the sheds use a very thin steel that doesn’t provide enough material for the screw to bite into, and the forces (particularly the vibrations from wind gusts) can cause the screws to loosen, or pull out altogether. Adding some rivets in strategic positions can greatly add to the overall strength of the shed.

I’ve found that even a weak shed can be given a significant boost by adding a wooden subframe.  This has a number of benefits – in addition to the significant overall shed strength, it provides a good structure for adding storage, and can be skinned on the inside with particle board, which then provides a perfect space to be filled with insulation (if desired / warranted).

Shed Construction – Foundation and Floor

I am currently writing some course notes for a shed building course that I’ve been asked to create for Holmesglen Tafe. The notes are kept pretty concise, so don’t expect pages of details, (they certainly could be – I could write a book on the subject- one day I might!)

Foundation Options

There are a number of options for the base of the shed, and what you end up choosing will be based on a combination of cost, location, and intended function of the shed. These obviously are closely related to the shed floor (and in some instances are one and the same). The forms that are available are obviously very closely related to the different options for house construction.

Dirt / Earth

In some cases, there may be no specific requirement for a shed floor, and therefore the foundations of the shed are thought to also be non-existent. This will very quickly lead to problems, and is definitely not recommended. That is not to say that an earth floor to the shed isn’t fine, and in some cases it is a good solution, but the foundation for the shed itself (under the walls) is still an important component.

A shed sitting directly on the ground is not only unsecured (and therefore highly venerable to wind damage), but is likely to corrode around the base very quickly. If you choose to have an earthen floor, you still need some form of foundation, whether this be on-grade, or concrete.

On-grade foundation

This form of foundation is particularly low cost, and very easy to construct. It isn’t strictly a permanent foundation, but never-the-less is quite suitable for shed construction. It involves placing the foundations directly onto the ground (a scoria bed, concrete or brick bed or earth) and on top of which is placed a treated timber frame (for the floor), or simply the shed walls themselves (and the floor can then be concrete tiles, or earth). A layer of damp course is strongly recommended, irrespective of the final choice. A bed of scoria or similar underneath is a good idea to aid drainage, and help prevent the foundation from sinking into the soil.

In any event, given the wind strength in Melbourne, it would be worth considering sinking a concrete pier in each corner (or pouring one) to have something to secure the shed to, rather than just relying on the weight of the shed to hold it in place in severe weather conditions.

Pier foundation

This is quite a traditional construction method, and is often used for houses, and decks. It involves sinking a grid of piers (concrete or treated wood) into the ground (often concreted into position), and then a wooden frame is constructed on top.

Concrete Slab

Another very common foundation (and floor) construction is the concrete slab. Even so, there are some different ways these are used (and laid). You can box up where the concrete is going to be poured, and once complete construct the shed on top, or take an easy route and build the shed on a basic form of on-grade foundation, then pour the concrete slab into the shed itself.

Sounds a bit rough and ready, but it can be effective, and you can be sure the shed isn’t going to be going anywhere after that! It is not my favourite solution. For one, it leaves the base of the shed particularly vulnerable to corrosion. On the other hand, the shed is secured down soundly, and it is very unlikely to have water penetrating under the walls.

Floor Options

This is closely related to the choices made for the foundations, and there are many variants available. These can include:

Earthen

The floor when you don’t need a floor. One advantage – cost.

Wooden Flooring

This can be floor sheeting (either a commercially available form such as yellow tongue, or simply particle board, or similar), or tongue and groove boards, or decking. In any case, some form of underfloor barrier is definitely recommended (builder’s paper or foil, or at least a roll of plastic). There are advantages to a raised floor – services can be run under-floor (electricity, plumbing, dust extraction (if the shed is to be a workshop) etc. Having under-floor insulation obviously helps in the variable climate conditions.

A particularly good choice for workshops etc when you are going to be standing on it for long periods of time – it isn’t as hard on the legs and joints as a concrete floor. On the other hand, it is more expensive, you need a higher ceiling for the space lost underfoot, and it isn’t able to sustain the sorts of loads that a concrete floor can manage. Some woodworking (and particularly metalworking) tools can weigh in around ½ a tonne.

Wooden flooring can be placed on top of a concrete slab, which does provide a bit of the advantages of both options.

Concrete Slab Floor

There are advantages and disadvantages to all the systems, and the concrete slab is no exception. It is generally very strong and able to cope with significant loads, and particularly if you are going to be moving items around. It is relatively cheap, and by using something like a dynabolt, items can be secured rigidly to its surface. On the other hand, it is harder to stand on for long periods, so some form of rubber mat or similar would be a good idea, and if you laid it yourself, it can be tricky getting it really level. If you overwork the surface trying to smooth it, you can also find you have concrete dust being produced for a long time afterwards as well. They are also quite cold in winter, and trap heat in summer. One thing that is often missed is to seal the concrete once it has cured, as moisture can still easily pass through the slab if this is not done.

Both my current sheds (and a previous shed) have concrete floors, because as much as a nice raised wooden floor would have been ideal, cost and functionality were also considerations.

There are various grades of concrete – 20MPa, 25MPa and 28MPa. The 28MPa is relatively expensive, whereas the cost difference between the first two is only a matter of a few dollars per m3, so I tend to err on the side of 25MPa. That, combined with rebar and a 75 – 100mm thickness results in a very robust shed floor.

%d bloggers like this: