Strip Footings, Void Forms, Piles

[psychoceramics]

I am contracting house construction in Western Canada and cannot get a clear answer on void forms. If the soil is fill down at least 4 feet to mineral clay and piles are required, does one use void forms to safeguard frost heaving? Second, is this code (Alberta) or just good practice? My engineer says no need for void forms.

 

[jrppr]

The answer I think will be highly dependant upon the type of fill(will ice lens occur), depth to water table, and moisture content and plasticity of underlying clay. The void form is needed if there is a risk of uplift from frost or swelling.

 

[VAD]

It also depends on whether your foundations are in a heated or non heated location. For patio decks which are often in non heated locations, there would be a need for void forms re conditions as mentioned by jrppr. In relation to swelling soils, if the propensity for swelling is present then the use of void forms is often preferable.

In general, there are other possible solutions apart from the use of void forms if one understands the ground conditions well. Your Engineer, I would believe, has taken these into consideration and you need to ask him his reasons.

Cheers