The site plan is the sheet that shows your house sitting on your block. It is the least exciting drawing in the set and the one that decides most of the surprises: retaining walls, the height of the slab, where the water goes, and whether the house you chose actually fits. Read it before the floor plan, not after.
A supervisor reads the site plan from the levels down. The little numbers scattered across the block are spot heights, and the difference between the highest and lowest one is the whole story. Under 300mm across the house footprint is an easy block. Over a metre and someone is building retaining walls.
Setbacks are the gaps between the house and the boundaries. They come from the planning rules for your zone and the estate covenants if you are in a new estate, and the site plan should show each one as a dimension from boundary to wall. Front setbacks in new suburbs are typically 4 to 6 metres to the house and 5.5 metres to the garage door so a car can sit on the driveway without hanging over the footpath. Side setbacks are commonly 900mm to 1 metre to the wall at ground floor, more for an upper storey, and often zero on one side in a small lot code.
The trap is the eaves. Setbacks are usually measured to the wall, but eaves and gutters can only encroach so far, and a 600 eave with a 900 side setback leaves 300 of air. If your neighbour has the same, the two roofs nearly touch and you have a gutter you can never clean.
Are the setbacks on this site plan to the wall or to the eave, and what does the estate covenant require?
An easement is a strip of your land that someone else has rights over, usually a sewer, stormwater drain or power authority. It appears on the title and on the site plan as a hatched or dashed strip, often along the rear or one side boundary. You cannot build a house over it. You can sometimes build a pergola, a shed or a fence over it with permission, and you will be asked to remove them at your cost if the authority ever needs to dig.
The common widths are 1.5, 2 and 3 metres. A 3 metre sewer easement across the back of a 30 metre deep block takes a tenth of your yard and pushes the alfresco forward. Check it before you fall in love with a plan that needs the full depth.
Is there an easement on the title, and does anything on this plan sit over it?
A contour survey is done by a licensed surveyor and shows the shape of the ground. Contour lines join points of equal height, usually at 250 or 500mm intervals on a house block. Lines close together mean steep. Lines far apart mean flat. Spot heights are the little numbers like 41.62, and they are in metres above the Australian Height Datum, which is roughly sea level.
The number a builder wants is the fall across the footprint of the house, front to back and side to side. Take the highest spot height under the house, subtract the lowest, and that is your fall. A slab on a block with 300mm of fall is a standard job. At 600 to 900 you are into a drop edge beam or a split slab. Past a metre you are into retaining walls, and past 1.5 metres you should be asking whether a split level design suits the block better than fighting it.
Look also at the fall relative to the street. If the block falls away from the road, stormwater has to be pumped or run through a legal point of discharge at the back. If it falls towards the road, the driveway may be steep and the garage may end up below the footpath.
What is the fall across the house footprint, and is any retaining wall included in the price or listed as an allowance?
Look for FFL, the finished floor level. It is the height of the top of your slab. The rules want the slab a certain distance above the ground around it so water runs away from the house, usually at least 150mm above finished ground, and more in some flood areas or where the ground is reactive. On a sloping block the FFL is set near the high side, which means the low side ends up with a step down to the yard, sometimes several.
Count those steps. If the alfresco is at FFL and the lawn is 600 below, you either have a deck, a retaining wall and steps, or a lot of fill. None of that is in a base price.
Somewhere on the site plan or the engineering there will be a soil classification: A, S, M, H1, H2, E or P. It comes from a geotechnical report where someone drilled a couple of holes and tested the clay. A and S are stable. M is moderately reactive, common across a lot of suburbs. H1 and H2 are highly reactive clay that swells when wet and shrinks when dry, which is the stuff that cracks houses across Adelaide's inner east and Melbourne's west. E is extreme. P is problem site, which can mean fill, trees, soft ground or a slope.
The class drives the slab design. A class M slab is a standard waffle pod or stiffened raft. H2 and E need deeper beams, more steel, sometimes piers, and the site cost allowance in a base price rarely covers them. If the class on the plan is H or worse, the words "site costs to be confirmed" in the quote are not a formality.
What soil class has the slab been priced for, and is that from a report on my block or an assumption?
The site plan should show the sewer connection point, the stormwater discharge point, the water meter, the power pit or pole and the NBN pit. Where they are matters. A sewer connection at the front on a block where the plan has the bathrooms at the back means a long run under the slab. A power pit on the wrong side means a trench across the driveway. A legal point of discharge at the rear on a block that falls to the front means a pump or a charged line.
Also look for the crossover, the bit of driveway between the kerb and your boundary. It has to line up with the garage, avoid the stormwater pit and any street tree, and it is often not in the builder's price at all.
Are the sewer, stormwater, power and crossover all shown, and which of them are in the price?
Existing trees are drawn as circles with the trunk in the middle and the canopy as the outer ring. A regulated or significant tree changes what you can build near it, and both states protect some trees by trunk size. Roots also matter for slabs, because a large tree drying the clay on one side of the house is a classic cause of one corner dropping.
The plan should show existing fences and the neighbouring houses as outlines, and sometimes their window positions. Overlooking rules, especially in Victoria, can force obscure glass or higher sills on upper floor windows within a certain distance of a neighbour's private space.
Are any trees on or next to the block protected, and has the slab design allowed for them?
The pages on BuildPilot this guide leans on.
The contour survey is the measured record of your block from a licensed surveyor: boundaries, levels, existing features and services. The site plan is the builder's drawing of the proposed house placed on that survey, with setbacks, finished floor level and cut and fill shown.
Under about 300mm of fall across the house footprint is a standard job. Between 600mm and a metre expect drop edge beams and some retaining. Past 1.5 metres a split level design usually beats fighting the slope.
Not a habitable building. Some authorities allow a pergola, shed or fence over an easement with written consent, on the condition you remove it if they ever need access. Check the title and ask the authority named on it.
Class H1 or H2 is highly reactive clay that moves with moisture. The slab needs deeper beams and more steel than the class M assumption most base prices use, so expect the site cost allowance to increase once the report is in.
Finished floor level, the height of the top of your slab in metres above the Australian Height Datum. It is set to keep the floor above surrounding ground for drainage, which is why the low side of a sloping block ends up with steps down to the yard.
Sizes quoted are typical for Australian residential work and are given to help you read drawings and ask better questions. They are not a specification. Your engineer, designer, builder and the National Construction Code decide what applies to your house.
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