Thursday, March 3, 2011
The use of ground screws in fence construction has been a widely accepted practice for more than a decade, yet the use of ground screws for decks has not been as well embraced. However, these innovative products offer significant advantages over conventional piles & posts or pad and post systems. They have evolved considerably in recent years, with a wider array of types and widths.
Consumers are well advised, however, to either consult with a knowledgeable supplier or research the best type of screw to use with each specific application, to avoid the risks associated with employing a screw, pile or post that is inadequate for the task. Many do-it-yourself decks are supported, in large measure, on good faith and not good foundation!
Simple, one-level smaller decks may well be adequately supported by a 4 by 4 post on a concrete deck pad. Even then, though, improper levelling can lead to unbalanced load distribution and shifting.
One step beyond pad and post supports is pile or pile and post supports. Piles offer the advantage over pads of distributing the weight into the soil below the deck, and providing an underpinning that is less likely to shift with varying soil moisture content and heavy deck traffic. In most cases for larger or multi-level decks, pile systems are the minimum standard to ensure stability, durability and strength.
But ground screws go beyond pile or pile-and-post construction, particularly for the home handyman. Simple ground screws can be easily removed and repositioned, unlike piles. With no digging, significant manual labour is eliminated.
Ground screws act in a similar manner to wood or metal screws. Their spiral allows for less force to be needed to insert the screw into the soil, while the increased surface area of the screw face provides more stable contact with the binding soil. This results in decreased frost heave and shifting due to dry or wet soil conditions. On the other hand, the screw is not suitable for some soils, such as those with lots of rubble, loose compact such as gravel or sand, shale, sandstone, dense or frozen soils.
In spite of these drawbacks, though, screws are more adaptable, and casnn be inserted in close proximity to overhangs, where piles could not be driven. Screws can be easily installed on slopes, and the light-weight equipment used for most applications is less disruptive than heavy pile-driving machinery.
Less digging and soil disruption means less waste left over and less cleanup and less noise during construction. Both screws and pre-cast pilings can be subjected to structural load immediately after installation, whereas poured-in-place piles require drying time.
In spite of the numerous advantage of screws, though, factors such as cost, building code requirements and aesthetic considerations need to be factored into decision-making. To ensure that your deck supports are properly designed, we advise that you consult with a building professional, to determine the application that is most appropriate.