Hi developers/builders out there,
What defines a “gentle” sloping block? Just looking at a possible subdivide-build property and the backyard does have a slope… To get a guesstimate, I counted the colourbond panels and the level of “steps” along the fence and there’s approx 9 x 10cm so if we round it up there is about a metre drop in the land from front to back, along a length of approx 28m. so does that mean 1/ 28 * 100 = 3.5% slope?
Is that roughly how to calculate?
If I’m right, by how much would a slope of 3-5% affect the price for building/site works etc?
Thanks,
EmmaHi Emma- a builder would be able to give you a good estimate. The cost depends on whether you are building the house on a slab or on piers- if it is on piers than it probably wouldnt matter a great deal but if it is on a slab then you will need to excavate, fill and build a retaining wall.
One thing to be careful of is that building height limits are typically based on the lowest point on the block. So if the lowest point on the block is significantly lower than where the new houses are going to be located, then you might need to cut a significant amount of dirt away to fit the building under the height limits.
Drainage can also be a problem because water runs downhill, and the rain runoff, sewer, drains etc need to drain towards the street. You can get around this by using sumps and pumps (or it might work anyway depending on the level of the main/board sewer) but it can be expensive.
3.5% grade sounds like a fair amount- that would work out to about a 2m drop in height from the frount of the house to the rear of the block baseed on a 40m deep development site.
Cheers,
LukeHi,
Probably doesn’t answer your question exactly, but on our plans of subdivision we must define the land slope by the following:
For the purposes of subregulation (1)(a)-
(a) level land means land where slopes do not exceed 3 degrees; and
(b) undulating land means land where slopes vary between 3-10 degrees; and
(c) steep land means land where slopes vary between 10-15 degrees; and
(d) mountainous land means land where slopes exceed 15 degrees.
This defines 0 degrees as being flat and then work either side of that.
Doing a bit of trigonometry on your block with ~ 1m drop over 28m. Angle = tan^(-1) x (1/28) = 2.045 degrees.
So actually by definition you’re on “level land”.Cheers,
Currently building on a slope.
Be sure to check with your local council, the one I'm working with will NOT allow pumps or detention basins.
I am forced to either build up the ground level (limited to 500mm, this will require a retaining wall and drainage works) or purchase an easment (my preferred method, which will cost me approximately 15k including pipework).I will probably avoid purchasing sloped land in the future unless I can get a really good price on the property, just not worth the headaches.
Hi Wisepearl
I would regard a 1 metre fall over 30 metres as acceptable – Ashley and Luke Good answers.
My question for you is which way does the Slope run – Towards the road or away from it ?
And the Second question is If its away from the road do you have a stormwater easement in the rear?
Then how is access and what/how do you intend to build – Slab on ground or Bearers and Joists (Timber floor)?
Lots of things to consider – also position of Power, Sewer and other utilities
I would do a through site inspection and get a surveyor to do a contour survey
Cheers
The block slopes away from the road, so aware of possible issues with sewer/drainage etc.
Most likely concrete slab for the house.
If I was going to proceed with this deal I would of course get surveyor out instantly and do full contour survey etc. But for early days of due diligence, I am just trying to figure out how much $$ buffer to add into number crunching for a gentle slope to see if the deal is possible or not.
thanks all for your comments and points to consider.
Depending on the land size you may not need a lot of retaining as you can batter away from the house. If the land is small then you will need to retain the block. If the neighbour has already built then you will need to keep your retaining wall away from the boundary. This will impact on your house design in terms of allowable width.
If is only a gentle slope away fron the street the head preassure will get water out to the street however, your yard gullies will not work so your back neighbour will get all your run off. Consider getting a underground tank in the front yard so the overflow should naturally drain to the street as long as the front as a slight slope to the street.
WisePearl
Had a thought – most builders allow for a 500mm cut and fill on a normal building site so there should be now additional cost in building.
Your extra costs will probably come from retaining walls or drop edge beams (if required) and access and removal of spoil. Trust this helps.
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