Heavy Duty Construction

What does it mean to say solid or heavy duty tables and and how do you compare between them.

Pictured above is our solid timber picnic table construction method. Our heavy duty tables used for parks and gardens take it even further by using 75mm thick frames and table tops and galvanised iron bracing struts!

Our solidly built tables live up to the reputation of being tough heavy duty outdoor timber tables - don't settle for light gauge inferior products. In the long term its false economy as the light gauge tables don't last !

Unfortunately the definition of heavy duty and solid tables is often very subjective and multiple claims are made on the internet that we find misleading. We have put together this summary to help guide users in comparing table construction.

Heavy duty is not just about the choice of timber but also encompasses the hardware used, the construction methods and final surface finishes.

Lets look at a few of these items in more detail.

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The choice of timber types :

Timbers in the 'Pine' family are often classifies as soft timbers. The have a low surface hardness and can be more easily scratched and dented than hard timbers. Hard timbers are the likes of : Red Gum, Victorian Ash, Tasmanian Oak, Ironbark, Merbau etc.

The point here is that the main difference with these timbers is surface hardness and tables can be made from all these materials that are heavy duty, solid or flimsy.

Within all timber types you also have a range of timber sizes or cross sections that can be used to make frames and tables. This is one area that can help distinguish between light and heavy duty. In outdoor timber tables anything that is made from 35mm thick timber or less, we would not classify as heavy duty as it simply is not. A good guide would be to classify heavy duty furniture as being made from 45mm or 75mm thick. In our range we also make furniture in 100mm and railway sleeper thicknesses of 125mm - these are made more for cosmetic appearance than to increase strength. You have probably seen photos of cars on tables and claims of heavy duty, well in comparison we could park a semi trailer on our furniture made from railway sleepers but that does not necessarily make it more heavy duty. Tables are built for people and not vehicles, and outdoor tables are should be built to withstand the elements !

In summary avoid timbers below 35mm thickness

If you are considering a light table made with 35mm thick timber, check for sufficient additional central support and bracing.

45mm thickness in timber is a good starting point to being called solid and/or heavy duty.

75mm thickness is a true commercial grade heavy duty table.

Anything above that is simply done for aesthetic reasons.

Special note on treated pine :

Treated pine is readily available in 2 categories, F5 and F7.

F5 is wet treated pine and is likely to twist, shrink and move as it dries. F7 on the other hand is seasoned treated pine which has already gone through the drying process before it is treated. F7 also tends to have fewer imperfections like knots than F5.

All timber if left in the sum will dry further and can still move and twist, but F7 treated pine will do this a lot lot less than F5.

We always use Stable F7 for our table tops and seats and you should insist on nothing less. Don't settle for cheaper builders grade F5 as you might regret it after the first summer !!

The choice of hardware :

Outdoor timber will be subject to corrosive elements. Even tables that are oiled, stained or painted will still get water into the joins and the corrosive/rot process will begin.

Normal steel fixing will rust and perish and should be avoided.

Zinc plated hardware is slightly better but still offers only minimal protection.

You should be asking for proper galvanised hardware if you want the hardware that holds your table together to last.

When looking at nuts, bolts and screws, there is also a range of thicknesses. Insist on 10mm galvanised bolts and a minimum of 14Gague galvanised screws.

In our view if it doesn't use hardware of at least the above specification it shouldn't be classified as heavy duty as again, its simply is not.

As good practice, in thicker timbers larger diameter bolts should be used. For example we use 12mm diameter bolts for fixing sleeper furniture.

A typical 8mm diameter zinc plated bolt costs $40c whereas a 10mm galvanised bolt costs $1.20. Over a complete table it all adds up, however we prefer to build to quality than economy because we want our furniture to last.

The choice of construction methods.

You can use nails, screws, bolts or rebates to hold timber together but in general :

Where there is stress on joins it should be rebated and bolted. Check for tight fits otherwise the value of the rebates are minimised.

Always select bolts over screws

Always select screws over nails and check how far they penetrate into the subframe

And never accept nails as a construction method for outdoor furniture

The choice of finishes

All timber will decay if left exposed to the elements. Some timbers faster than others.

The biggest non human threat to outdoor furniture is water and moister. While the surface may dry off after a light shower of rain, the joins and contact point hold in the moisture for a considerable time afterwards. Painting the top surface of a table is great but in reality this top surface is the first to normally dry. Painting the joins would be of a lot more value, but is often unpractical and few people paint the undersides and in joins, cracks and gaps where water is normally trapped.

For sheltered areas, the choice of timber may not be as important, but for outdoor exposed areas the choice of timber is critical.

In relation to weathering, we would recommend selecting treated pine. It has been designed to withstand the elements and has heavy duty qualities in that regard.

Following this we would recommend red gum, followed by iron bark and other hardwoods.

If in doubt have a look at an old hardwood fence and you will see that the hardwood has perished but the red gum is still as firm as the day it was erected.

UV :-

UV light harms timber just as much as it harms humans. Direct exposure will grey and dull the surface. A dull surface will retain moisture longer.

Paints :-

To prolong the life of the timber it should be treated with a barrier to minimise water penetration and if it's dressed to minimise UV saturation that can cause greying.

Sawn surfaces can be painted, stained or oiled.

Dressed surfaces can be oiled or coated with something like Cabot's marine grade polyurethane.

Oiling lasts for months before it requires a top up, paints and polyurethane last for years.

Paints are soft whereas a polyurethane finish has a hardened surface.

In summary, to be heavy duty in relation to weathering choose treated pine as it has been chemically treated to resist rot, and its economically cheaper to build with.

In sheltered areas a good heavy duty surface choice is a polyurethane finish.

We do provide a staining treatment for our tables, for more details refer to our staining guide.

With so many people trying to cut corners these days, you need to ask about the quality you are getting and not just assume!

We believe in quality over economy, solid rather than flimsy. The furniture we make will stand up and surpass the best of the competition.

Check out our heavy duty picnic tables

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