In my experience, there is usually a requirement that the foundation be able to withstand a storm surge which usually requires the use of piers or some pretty clever spill-way devices.

IMO building on a seashore is a job for an experienced local design professional.

ditto what he said. I don't understand how you 'only' have to go down 2 1/2 ft. Here in the US in the north, you have to go down at 'least' 4ft.

There are no special regulations here for shoreline building. Most homes are on full basement or crawl space but some have water problems during storm surges. I'm not interested in that possibility.

In clay and regular soil we need the footings down four feet. Apparently frost does not act the same in sand and only 3.5 feet are required. If I dig down 2.5 and add a foot of fill on top I was told I would be fine. The water table is about three feet down and I want to stay away from problems there.

Agree that it sounds like a job for a pro. The floor of a pier house should be insulated to the same level as the walls. Thats the easy part though.

The real trick is air sealing it to the same level as you could get with a filled stemwall which would be my vote not knowing anything about your local conditions or situation.

I am in the process of building on a lake in Northern Ontario. In order for our plans to be approved by the governing body of the lake all openings had to be 30 cm above the 100 year water mark.

We debated piers vs engineered slab. We decided to go with engineered slab over piers based on recommendations by 2 engineering firms as well as cost.

We obviously live in a cold wet climate and I know that came into play with the engineers recommendation, along with wet shifting soil.

I felt confident in our decision after consulting with the engineers.

HTH!

You are close to the coast and have a three foot water table? Definitely hire an engineer. There are many things that can go wrong here.

Think carefully about drainage, about where the water would go if you get a hurricane during a high tide. Water has to go somewhere, you want to direct it through. The advantage of piers is if you do them right water can go under the house. The disadvantage is I can imagine all sorts of problems with ice in a cold climate.

Plant a lot of shrubs that send out runners along the coast for erosion control. See if you can get permits to put boulders on the beach to break the energy of waves.

HTH
I like the idea of pier and slab. I will do more research on that approach. Have you got anything you can send me on this option.

ed
We have lots of beach grass growing which we will not touch. Boulders are an option but nature created a burm about two and a half feet high which has been there as long as locals can remember. As we are on an inner bay the major storms do not have the force that the ocean side gets

If I dig down 2.5 and add a foot of fill on top I was told I would be fine.

By local building officials? Although clean sand is less susceptible to frost heave than other soils, whatever foundation you put in will be so close to water that it will likely rise along the foundation/piers and freeze.

Even a casual vacation property costs enough to warrant an expert opinion.

This post was edited by worthy on Wed, Dec 24, 14 at 14:59