Archology

Building a House on Sand

As the parable states, building a house on sand is a risky proposition. And so, you probably will want to ensure your builder has builders public liability insurance – otherwise this will be a costly build. Sand itself isn’t the problem, but the proximity to water can be. It all comes down to flooding, and there are basically three types of foundations used in the beach area depending on your exposure, all of which you have to take into account when you are planning to build your own house.

The simplest foundation is the one almost everyone everywhere has because it’s cheap and simple. It’s a spread footing, a foundation wall that sites on a concrete beam set down below the frost line (depth will vary based on climate.) It’s simple, it’s cheap, it’s strong, and for anyone not actually in a flood zone, it’s all you’ll ever need. If you looking for recommendations then why don’t you check out someone like dfw foundation repair for those times when a crack becomes a problem in your house foundation.

A lot of homes near water are in what’s known as the 100 year flood stage of a river. This means that the kind of storm you’ll get, on average, once a century will cause water levels to rise to the point that they will flood your property. If you’re next to a flood ditch, river, inland bay, lake, or other body of water without waves, all you have to do is elevate the house above the probably elevation of the water. This elevation is all spelled out in FEMA maps and local codes, and can mean elevating a house a foot or two to 10 feet. The good news is, the foundation can be simple and cheap and just a spread footing, the only change is you have to install flood vents in the bottom levels to allow any water pressure to equalize between the interior and exterior of a house. There are restrictions in what you can place in the way of this water (no plumbing, mechanical systems, electrical systems, living space, etc.) but otherwise, it’s fairly easy on the designer and the pocket book. If your house has to rise more than 5 or 6 feet, it may be worthwhile to consider going to a more advanced foundation known as a piling. A piling is basically a large treated piece of wood that is driven into the ground and holds the house up by the friction of the soil. There are other types of pilings, but the wood friction pile is the most common form of residential piling. This has the advantage of raising the house up cheaply and getting all major structural and mechanical elements well above the flood stage limiting the amount of repair work you would have to do if your downstairs floods.

Some lots will require pilings those, and those are the lots that are on oceans or other wave producing flood zones. Piles are required here because, well, simply put, what happens when a wave hits a wall? The wall gets knocked over. Maybe not on the first wave, but in a flood situation, it would have to resist the water pressure and the wave action for house, and very few structures are truly up to that task, so the pile raises the entire structure above the waves and the waves generally flow around the pile without doing large amounts of damage. In my experience, it’s these houses that become the most tricky to design, both structurally and in meeting owner expectations, especially when adding onto a home that predates these restriction.

So now you know more than you ever wanted to about the invisible (most of the time) pieces of structure that hold up your house and when you need each. Piles aren’t just for flood prone properties though, I’ve also used them when trying to elevate a structure for design purposes, and in locations where the soil is really awful for a normal footing. There is also something called a grade beam which is basically a concrete spread footing supported by pilings that are buried below grade, and when to use that expensive system will have to wait for another day.