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building on a sloping block



How to determine the slope when building on a sloping block.


Let’s be honest: perfectly flat land isn’t too common.  Most domestic land packages and rural properties have a certain amount of fall across them, and it’s very easy to underestimate this figure.  Building on a sloping block is not difficult, but it’s super important that you have some idea of the amount of fall on your land before you launch into your new home project.


This blog isn’t about measuring the fall of your land using hi-tech surveying equipment.  Ultimately, GPS level systems with theodolites and laser level systems will give you extremely accurate levels, to within millimeters.  However, here we’re simply talking about how to take a rough estimate.  Of course, accurate measurements will be needed before construction can begin, but if you can get some idea of how much your block slopes, you can bear this in mind when planning your site layout, home design and landscaping.


What is Land Slope?


Slope or Fall generally refers to the amount of incline across a certain footprint of land.  A steep slope means that there is a sharp incline; gradual slope means that the incline is more gentle.


Calculating Slope Without Hi-tech Equipment


When trying to assess the fall of a piece of land, it’s best practice to have two or more people present – 2 people looking at the same area of land from 2 different positions can greatly help gain a better undernstading of the levels. 
So there’s 2 key things that can help you start to analayse the slope of the land. 


  1. Is there a body of water around that you can use? Water always finds its own level perfectly, so using a dam or lake, or a slow-flowing river or creek is a great way to compare the slope of the ground with the water level. Crouch down next to the water, and look over at the area that you’re trying to analyse. You’ll quickly see any variance. 
  2. Are there any existing buildings around? Unless it was something that Jack built, generally every building is constructed level. So this means that you can use either the roof, or brick-lines, window sills, decks, railing in cattle yards, etc, as references to compare the slope of the land. When using a building, it’s often best to stand on the side opposite the building, and look over the land you’re analysing with the building in the background – once again, it won’t be hard to see the variance. 


Then there are some tricks of the trade you can use to get a bit more specific. 


  • Use a pump bottle of water (ie, 750ml water). Make sure it’s at least 2/3rds full, and turn it on it’s side with the seam along the side. Water finds its own level, so if you look along the edge of the bottle and try and hold the bottle as steady as you can, you’ll be able to use it like a spirit level – when the water’s aligned with the seam on the side of the bottle (or a bubble in the middle of the bottle if it’s full), then you know the bottle’s about level. Sight along the bottle to a point in the distance of the land you’re looking at, and you’ll be able to get an idea od the slope.
  • If you’re comparing the slope of the ground to an existing building, try these tricks: 
    • Count the bricks
    • Count the rows of cladding
    • Get your helper to stand over next to the building to use as a height reference
    • Count the hay bales in a hayshed
    • Look at the slope from 4 completely different angles, and from both close up and far way. Sometimes a slope might look gradual, but you’re actually looking at it from another spot which already has a slope on it, so it becomes exaggerated. Where there are existing steep slopes, don’t be deceived about a so called ‘flat section’ in the middle of it all – you’ll find that it’s probably still got quite a slope on it, but it just appears to be flat because of the surrounding slopes.
    • Trees generally grow straight up. You might think that they bend and twist all over the place, but on a steep slope, if you stand right back you’ll find that the overall alignment of the trees are level – once again, this can be a good guide.
    • Always be conservative. If you reckon the slope over the footprint of where you’re going to build the home is 1 mtr, estimate 1.2mtrs instead. In our experience, we’ve generally found that the slope is steeper than originally estimated. 
    • As a last resort, you can download an app on your mobile phone that has a spirit level showing on the screen. The level is accurate within itself, but because the phone is so small, and it’s only showing on the screen, it’s very difficult to get any broad use out of it. But if you can get a long piece of timber or something like that to use, then it can be of some use. 
    • And you may have to estimate the slope in stages, espcially if it’s steep. As an example, you might use your water bottle to sight along and you guess that it’s a 1.5mtr slope to that point. Then you walk over to that point, and sight up the next point, which is another 1mtr, etc, etc. 
    So, if you are building on a sloping block, have fun trying to estimate the slope on the land, and always remember, no land is perfectly flat – although you won’t have to worry about the curvature of the earth!

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