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footings cost extra


No two building sites are the same – they always differ in some way or another. And because of this, soil tests generally always differ. And one question we get from time to time after the soil test comes back is why will my footings cost extra because I’m near trees? and another one is why will my footings cost extra because an old home is being removed from the spot where I’m going to put the new one?


They’re both good questions, and we’re going to try and answer them for you in layman’s terms. Bear in mind that we’re answering them based on stump footings, but the same principles apply with slab footings. And we’re also mainly talking about the presence of big trees and a number of them. If you’ve got a couple of smaller fruit trees nearby, then that’s not going to affect anything. It’s the long rows of big pine trees or clusters of huge redgums that are central to our story.


We’ve got another blog about soil tests which is well worth reading and will complement this blog. In that particular article, we talk about the various characteristics of soil and how they impact the building process, and one thing in particular, is relevant to this blog – moisture content. And that’s the guts of why you’ll need to pay a bit extra for the footings where there’s trees present or trees and / or old house being removed – because of abnormal moisture conditions.


In engineers language, they call this AMC’s, and it comes from a clause in the Australian Standard that covers footings and soil tests. These abnormal moisture conditions can be as a result of a few things, including what we’ve just talked about, but also including drains, wells, and even old septic systems that are being removed.


And what happens is that the different moisture content means that the soil will move – or could move – more than it would otherwise. Now you might say, other than what? That’s another good question, and the answer to that is ‘other than if the trees etc weren’t there’.


So what happens is, the geotechnical engineer takes samples of the soil, and determines what the ‘normal’ soil is, and then considers the abnormal. The normal soil may be quite stable with a good bearing pressure, able to hold up the home nicely, and have minimal movement from side to side, so it’s technically classified as good soil. Of course, it may also be a highly reactive soil in its normal condition. But this first step is to look at it in isolation as if the trees etc weren’t there.


But…those jolly trees can really muck things up. The engineer will look at the size of the trees, how far away they are, and then do some calculations to determine the potential impact. And it’s the same with an old home being removed. What’s the size of it, type of footings, and then look at the impact.


Extra moisture or fluctuating moisture can cause the soil to move more than it would normally, and so the engineer then takes this into account when designing the footings for the home. The typical result is a deeper footing, or at least deeper within a certain distance from the trees or where the trees / house were. Sometimes additional reinforcement is also needed. It all depends on the specific findings from the soil test.


So of course, deeper footings take longer to dig and they hold more concrete, which ultimately costs more. How much more, you ask? That’s a difficult one to answer, but for an average home, maybe an extra $2,000 to $3,000. But it can really vary a lot, depending on the size of the home, the characteristics of the soil, the subfloor structure layout, how many stumps the load is spread over, etc, etc.


The simple thing to remember is that it might hurt your back pocket a bit at the start, but hey, isn’t it better to know that you’re on solid ground for the long-run?

Disclaimer. This blog is our opinion only. The information provided in our blogs is accurate and true to the best of our knowledge, but there may be omissions, errors or mistakes. The information presented in our blogs is for informational purposes only and we are not professionals, so the content we provide shouldn’t be taken as legal advice. We strongly recommend consulting with a professional before taking any sort of action. We reserve the right to change how we manage our blog and we may change the focus or content at any time.

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