6 Building A Patio You Can Be Proud Of

More than ever, Australians are spending time in their back yards. If you’re thinking of building a patio, I’ve put together a quick do-it-yourself guide that you can follow, to help you avoid getting confused and lost along the way.

Here is a quick run down of what you’ll need to do.

Firstly, you need to get on the right side of your local Council. When submitting your building application, the Council will usually request 3 things:

  1. A site plan at a minimum scale of 1:200 showing the location of all existing buildings and the proposed structure(s).
  2. Plans, sections and elevations at a minimum scale of 1:100.
  3. Sectional details of the proposed structure(s), including type, size, stress grade, spans, spacing of members, connections and footings at a minimum scale 1:50.

The site plan

The site plan is usually on file with your Council. After a quick phone call to them, they should be able to send it out to you. After you receive it, simply use a pen and ruler to draw neatly where your patio will be placed in relation to your house.

The plans, sections, and elevations

This is where you can again get artistic with a pen and ruler. Simply get a blank A4 piece of paper and a black fibre tip or biro pen (black because we need maximum contrast between the black of the pen and the white of the paper) and do a neat scale sketch of your new patio – one view from the side, another view from above, and a third view through the middle of it. You should note on it the dimensions of the sides – the length, height, and width of the patio. Include the shape and slope of the roof on the section (through the middle) view.

Getting a draftsperson

If you don’t have the time to do a neat dimensioned drawing, you can find a local design draftsperson (a local one is better because they may need to visit your house to see exactly how you want the patio to be built). I’ve found that the better design draftspersons usually have some working knowledge of structural needs so they will be able to advise you if something is unrealistic or may work out to be too expensive.

Keeping your costs down

If you want to keep the construction costs low, the cheapest in terms of construction and engineering costs will often be a steel framed patio built from patio tube (76mm x 38mm hollow rectangular steel). If you keep the size under around 6m in width and with a spacing of less than 4m between the columns, a basic universal design can be used from almost all the lightest, most affordable sections.

Larger sizes are of course possible, but the construction and design cost will increase exponentially the larger it gets, so staying within the norm is good for those who want to save money.

Longevity

The most common and durable material to construct your patio from is steel patio tube. Timber patios are susceptible to rot, termites, and eventually sagging and bowing of the timber members. Although they may look great when constructed, after 20 years a fresh coat of paint won’t help them. On the other hand, steel members will last you much longer and any restoration work required will be much easier.

Getting the engineering specifications

Once you have a drawing of what you’re after, you can approach a Structural Engineer like ourselves to get the structural specifications sorted out. If your patio is small and within common sizes, we can supply you with a low cost, economical, universal design that will cover all common shapes and sizes. We created these to save you money and time if your plan falls into its specifications. If your patio design is out of the ordinary, some time will be required to prepare the specifications for you.

Getting it built

Once you have the structural specifications from an Engineer, then it’s time to approach a builder. You’ll now know what materials you’ll need, and the builder will be able to quote you properly and accurately.

Conclusion

Getting a patio up can seem a bit confusing at first, but the process is quite straight forward. I think people often can become frustrated and delayed just because they don’t have the right information on hand, but it’s easy when you know the steps. So get out your pen, and start sketching!

Do you have any questions about getting a patio built?

Secrets of Cost Effective Shed Building

I think you’ll agree with me when I say that the Australian Shed market is fiercely competitive. It’s really hard to get an edge over your competition and still keep the quality of your sheds high. If you’re a shed builder, in this article I’ll provide some quick tips you can use that can increase the quality of your product and effectiveness of your sales process while reducing your costs.

Quoting Jobs

You should have an idea of rough rafter, column, footing, and purlin sizes for common shed spans that you quote on often. That way, you’ll save time when quoting to new clients, as you won’t have to wait for a response from your Structural Engineer to confirm section sizes. I can provide you with simple tables that you can use for quoting purposes but often these shouldn’t be needed if you have some experience.

Footings and slab

There are many ways you can make your footing and slab design more economical before it even passes over the desk of an Engineer. You can dramatically reduce the size of your pad footing when a slab is provided over the top instead of paving or gravel. You should confirm with the client whether or not they intend to use a slab with their new shed and inform your Engineer of this so they can save you money in footing construction costs.

I’ve found that the most economical pad footing shape is generally a cube. This balances uplift resistance with overturning resistance and material costs. For small sheds, you can skip the pad footing all together and simply use a raft slab with the shed anchored directly to the slab which can save you money in construction costs. Cast in footings generally perform better than baseplates or cleat footings, if your construction schedule allows for them.

Steelwork

Purlin and girt spacings can vary depending on wind conditions. You can space your girts further apart towards the ground, and your purlins can be spaced further apart away from roof edges.

You should keep in mind that sheds must be braced in all directions. I usually specify knee braces where room is needed between the columns and the columns aren’t too high. Cross bracing is generally more economical and stronger. For smaller spans, the sheeting itself can be used to brace the building. When you’re selecting cross bracing, if the area is trafficable it is preferable to use round bar instead of strap, as the strap bracing can be an injury hazard.

Get your Engineer to evaluate wind loads and shielding on a site by site basis. Maximum loadings from the Australian Standards and Building Code of Australia do not apply to most sites.

For connections, you can use Tek screws instead of bolts for smaller span members. Sometimes it can reduce your manufacturing costs to replace thicker cleats with back to back smaller plates.

If more headroom is requested by your client, deeper C sections can be replaced by back to back shallower sections.

Do you want to provide a lean-to along one side but don’t want additional columns in the way? Simply extend the rafters out over the top of your columns.

Live-in sheds generally should be built sturdier than storage sheds or workshops, as deflections due to wind loads may wake the occupants at night, causing them to request remedial work that could have been avoided!

If your client wants solar voltaic panels on the roof, they can generally be affixed to an extra set of purlins. Hot water tanks however should not be placed on the roof as they are cumbersome, heavy, require additional steel to support, and leakage can corrode the roof steel.

Also, when using cold form steel, if you wish to miss a column and use clean-span beam instead to support the rafter, remember to use back to back sections for the columns each side of the clear-span as they need to support double the load of the rest.

Do you know of any other helpful tips for building sheds more economically?

Improving the performance of your concrete mixes

Concrete is generally fully hydrated at about 25% water:cement ratio. But that needs to be water available to the cement. In practice a significant amount of water is absorbed in wetting the surface of gravel & sand. So the water content is increased to about equal, by mass, to the cement content.

This assumption that more water is needed to account for that absorbed by the the non-cement components can go wrong if the other items are already damp or wet, for example, from overnight rain onto the stockpile of aggregate & sand. Good batching plants take wetness of aggregate & sand into account, but bad ones may not, leading to too high a slump, and weakened concrete.

So far as we are concerned on a daily practical basis, to improve strength, durability, and performance in general: Slump needs to be minimized. Entrained air should be expelled (vibrate). The concrete kept cool & damp while curing (pond).

Slump

Assuming that the concrete supplier has provided the right specifications. As the slump increases, the strength is reduced, the porosity is increased, and shrinkage cracking is increased.

Unfortunately, standard slump from some suppliers is now 100. But other slumps (preferably lower) can be specified, but may be ignored by the supplier. I’ve known design slump values to be ignored, and slumps as high as 140 to be delivered (by well known national companies). You may not even be present when such a slump is delivered, and it may be denied later.

But assuming that they will deliver the design slump, then for critical use, such as suspended slabs, polished concrete, and corrosive environments, the ideal design slump should be about 60. That is too low for workability, and there’s a risk that the concreter will stick a hose pipe into the truck. So the slump is specified as 60 brought up to 100 by superplaticizer Adva 145 (or similar modern additives). That tells the supplier to produce a concrete mix with 60 native slump but add sufficient superplasticizer to improve workability to 100 slump. Modern plasticizers have no significant deleterious effect on concrete, if used in moderation, and a can is carried in the truck to add at the work site, if the slump is still too stiff. If the concrete has a long way to travel, and may begin to ‘go off’, then a little retarder should be added at the yard.

Of course, it is possible to have high slump, due to excessive water, and maintain 28 day strength by adding more cement into the mix. But this also increases the shrinkage & cracking rate (as well as cost), since they are directly proportional to the cement content as well as the water ratio. So it is best to use low slump & increase it only with superplasticizer, such as 60 brought up to max 100 with superplasticizer.

Vibration

As the concrete is tumbled in the cement truck, and as it is poured out, it is full of air bubbles, which due to surface tension are reluctant to simply rise & escape at the top. Strength, durability, and workability are significantly increased, even with shallow slabs, if a vibrator is used (see graph). There are some excellent models now sold, with little engines or even electric motors, that look like a whipper-snipper. They don’t have a compressed air umbilical to drag around, are light (even carried in a backpack) and easy to operate. Concreters should start getting into the habit of using them, and I think they’ll be fashionable in a few years for everything from strip footings to ground slabs. (Remember, in the past it was standard practice to pull up mesh with a hook. Now we almost always use chairs).

Vibration also improves adhesion of the concrete to the reinforcement, because any loose dust on the reo bars is shaken off into the concrete as it scours the surface of the steel.

Vibration encourages concrete to fill all nooks & crannies, improving surface finish against formwork.

Furthermore, vibration reduces the occurrence of hairline cracks by reducing the stress points caused at strings of bubbles which become a weak fracture line. (uniform, deliberate air entrainment is more controlled & has specific uses)

Cooling & keeping damp

This is a a special problem for Australia. Particularly ground slabs poured in the summer, which are badly affected by over-heating: The ground they are poured on was already warm. They are at ground level sheltered from the breeze. The Sun blazes down on them through the day.

Thus the concrete cures too fast, and also unevenly; with pockets of dehydration. Surface crazy cracking is often the result. The concrete should be kept damp & cool for at least the first few days after the pour (see graph).

Sprinklers are no use; the spray is blown willy nilly. Sealing the surface with something such as a silicon spray is only a partial problem; it stops/reduces evaporation, but if anything, increases the heating of the slab, often bringing the temperature to close to boiling point. (Note; this is a different situation from autoclaving, which is used in controlled conditions for rapid, even, humid curing).

The only satisfactory way of keeping a ground slab both cool and damp is by using a small bund all around the edge & ponding with a few centimetres of water (see graph). For best results, this can be done once the slab is sprayed with silicon sealant.

By & By:

But nothing will save you if you don’t use enough steel, as in the photo below:

How many design errors can you spot in the above photo?

(I think the ‘engineer’ had shares in a steel company, eh? 😉

Author: Sam Nejad

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2 Tips for engaging a structural engineer

Tips for owner builders on engaging structural engineers:

1. Have drawings or neat sketches showing what you intend to build.

Especially when dealing with people over the internet, it is essential to first have a drawing or neat sketch showing what you intend to build. This drawing should contain all relevant sections (sizes of members etc) and dimensions (eg. length and width of your building) on it. That way we can quickly and accurately assess what needs to be done, and often it will save us having to do new drawings which will lower the cost involved.

2. Know what the Council or regulating body is requesting be certified.

Often the council will only require certain elements to be checked and certified by an Engineer. Knowing what needs to be done and what does not will save time and money for yourself.

3. Know the soil class.

If your building has footings and/or a slab which will need to be designed, knowing the soil class of the site will be required for the footing and slab design to be finalised. It is preferable that you contract a geotechnics company to conduct a site inspection before engaging a Structural Engineer to do the design work. If you do not know the soil class, you will need to inform the Structural Engineer so that they can arrange the inspection. This is also true for buildings which often do not have a typical footing, such as limestone retaining walls.

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