Setting out in construction is the stage where accurate marks decide whether a build starts right. Get the first marks wrong and every trade that follows inherits the error, from walls and drainage runs to floor levels. Most site teams use one of three methods: a chalk line, a string line or marking spray. Each one suits different surfaces, lengths and durations, so the right choice depends on the job in front of you.

This guide compares the three methods for the jobs you’re likely to face on site. You’ll see which option suits interior fit-outs, brickwork and groundworks, and when using more than one makes sense.

Setting out is only one part of site work, so you’ll also need the right kit. Our site equipment range covers the tools that support it.

Setting Out Methods at a Glance

Method	Best for	Strengths	Limitations
Chalk line	Flat, indoor or dry surfaces	Fast to apply, leaves a clear straight mark, easy to sweep away	Washes away in rain, creates dust, doesn’t suit rough or wet ground
String line	Long, straight runs such as brickwork and drainage	Gives a physical edge to measure from, reusable	Can be knocked out of alignment, needs tensioning and fixed pegs
Marking spray	Groundworks, roads, trenches and utility routes	Visible outdoors, lasts for weeks, works on rough ground	Needs drying time, harder to remove than chalk

Site setting out rarely relies on a single method. Each method suits a different job, and none is best across the board. The table shows where each one earns its place.

For the full range of setting out equipment, see our survey equipment range.

How Chalk Marking Works on Site

A chalk line is a reel with a coil of line dusted with powdered chalk. You pull the line taut between two points, lift it, and let it snap against the surface. The line leaves a fine, straight mark that’s easy to follow.

This makes chalk the quick option for flat floors, ceilings and internal walls. It’s ideal for marking out partition walls, tiling layouts or floor screeds where the surface is dry and stays dry. It’s less suitable for rough or wet ground, because rain and dampness wipe the mark away quickly.

Keep the chalk dry and check the line is clean before each use. A damp or gritty line gives a blurred mark, which can cost time when you come to set out the next run. You’ll find chalk, crayons and pencils for site marking in our chalk range.

Choosing the Right Option for Brickwork and Groundworks

Brickwork and drainage need a line that stays put for hours or days, not minutes. A string line is stretched between pins or stakes to set the course level or the run of a wall. Because it’s a physical guide, you can lay materials directly along it, and the line can be moved as the work progresses.

Drainage and levels are where string lines earn their place. The line gives a continuous reference over long distances, so small errors show up early. Check that the pins are secure and the line is tensioned, since a slack or knocked line will put the work out.

For longer or more demanding runs, polypropylene rope for long runs can cover distances where a chalk line becomes unwieldy.

On groundworks, the ground is often rough and wet, and a chalk or string mark can be lost before the work is done. Marking spray keeps the lines visible for longer, so it is the better choice for trenches, roads and utility routes. For smaller marking jobs, 750ml marking spray paint comes in a can that is easy to carry on site.

Which Method Fits Each Job

Start with the surface and how long the marks must last, then match the job to the method below.

Job type	Recommended method	Why
Interior fit-out on flat floors	Chalk line	Quick, clean and suited to dry indoor surfaces
Brickwork and block alignment	String line	Holds a straight, level reference along the full wall
Drainage levels	String line	Holds a level reference over long distances
Trench lines and utility routes	Marking spray	Stays visible on rough, wet ground

Upfront Cost vs Total Cost on Site

The cheapest reel is not always the cheapest option on site. Compare the upfront cost of a tool with its total cost, which includes refills, paint, re-marking and the time lost when a mark is ruined.

A chalk line is inexpensive to buy, but it needs regular refilling and a clean line, and a ruined mark can mean stopping work to check levels again. For a durable option, a 30m metal reel costs more upfront but stands up to heavier daily use. A 30m die-cast reel with a rewind button makes it quicker to retract the line at the end of each run.

When you work out total cost, count the time a crew spends waiting for a mark to be redone, not only the price on the shelf.

Can You Use More Than One Method on the Same Job?

Yes, and many sites do. Setting out is rarely one step, so a single job can need different marks at different stages.

Take a new build. Chalk lines suit the internal layout, where floors and walls stay dry and the marks only need to last until the next trade arrives. A string line takes over for the brickwork, holding the course level along each wall. Line marking paint then handles the external works, such as drainage trenches and access routes, where the marks must survive rain and rough ground.

Learning how to set out a building means tying the method to each stage. When the surface or the time frame changes, change the method too.

Conclusion

The right marking method depends on the surface, the distance and how long the marks must last. Chalk suits dry indoor work, string lines hold long straight runs and marking spray covers rough or outdoor ground. You can find the kit for each job in our full range of site equipment.

Frequently Asked Questions

What is setting out in construction? 

It is the process of transferring a building’s design onto the ground, marking the position of walls, foundations and levels before work begins. Accurate marks let every trade work from the same reference.

What is chalk line used for in construction? 

A chalk line transfers a straight mark onto flat, dry surfaces such as floors, ceilings and internal walls. It is quick for layouts such as partition walls and tiling.

Is chalk line colour permanent? 

No. Chalk marks are designed to brush or wash away, whatever their colour. If a line must last, use marking spray instead.

Does chalk survive rain on site? 

Rarely. Rain and damp wash chalk marks away quickly, so use marking spray for outdoor work that must stay visible.

How to mark out a building site? 

Start from the design drawings and the site survey, then mark the main lines and levels using the method that suits each surface. Check the marks against the drawings before any trade starts, so errors are caught early.