Flatwork
TLDR
- Pour on 4" of compacted fill - thicker in some cases
- Use 4" thick concrete with reinforcement (wire mat or rebar) - thicker in some cases
- Pick your finish: broomed, smooth, stamped, colored, etc.
- Concrete must stay moist to cure properly
- In hot/dry weather, cover or mist to prevent rapid drying
- Tool or cut control joints quickly after pouring
Overview
Flatwork refers to any flat poured concrete surface like driveways, patios, sidewalks, and floors. They serve both structural and aesthetic purposes. Many flatwork contractors also handle hardscaping like landscape stairs, flagstone paths, and pavers.
Flatwork is one of the most visible and frequently used parts of a project. It must be properly prepped and poured. Residential slabs are typically 4" thick and poured over 4" of compacted fill but some slabs like a "slurry slab" or "rat slab" are thinner, only meant to provide a basic floor for crawl spaces or sheds. Reinforcement with rebar or wire mesh prevents cracking and shifting. Finish options vary from plain gray with a broom texture to decorative stamped and dyed patterns.
Prerequisites
Excavation must be complete with a flat, compacted subgrade. Sumps, underground drains, and sleeves must be installed. Don't forget to dig any point load footings and install reinforcement for those before pouring. Determine the style before pouring:
- Surface - broomed, smooth, stamped
- Edges - bordered or not
- Control joints - tooled or cut
- Color - Natural or dyed
- Others - Exposed aggregate, ground, sealed, etc
Materials / Tools Needed
- Tools
- Wheelbarrows
- Trowels
- Screeds and Floats
- Brooms
- Buckets
- Shovels
- Come-along
- 6-mil plastic
- Materials
- Forms
- Stakes
- Concrete
- Water
- Reinforcement
Process
- Excavate and compact 4" of fill or gravel sub-base
- Set formwork to define slab edges and final height
- Install reinforcement (wire mesh or rebar)
- Order and pour concrete – confirm mix with supplier
- Screed and level the slab
- Apply chosen finish (broom, trowel, stamp, etc.)
- Add control joints to prevent cracking (tooled or saw cut)
- Keep concrete moist to cure properly: use mist, cover, or curing compound
- Remove forms and clean up edges after curing begins
Inspections
Compaction Inspection - Many jurisdictions require a compaction inspection before pouring a slab for a building floor. The inspector will want to see compacted subgrade at the specified depth (4+" thick) and 6-mil polyethylene plastic sheeting over the crushed stone for any habitable space. Not required for sheds, garages, porches, etc.
Best Practices / Pro Tips
Use a broom finish for walkways and driveways to provide traction. Often the moisture in the concrete or in the ground is enough for it to cure properly, but sometimes extremely hot or dry weather can cause problems curing the concrete. If that happens you can mist the concrete with water to keep it moist but you MUST keep it moist and avoid shocking hot dry concrete with cold water or it may damage the slab. Other options can be to cover it with a tarp or coat it in a waxy coating to prevent drying for a while.
Always plan your control joint layout ahead of time—they help prevent cracks and make the slab look finished.
Client Interaction / Communication Notes
Help clients choose their finish style in advance. Let them know that concrete color can vary slightly from batch to batch and that cracks are common but typically not a structural concern. Explain that concrete needs time to cure—keep foot traffic off for 1–2 days and vehicles off for a week unless using a high-strength mix.
Common Issues and How to Avoid Them
Drying too quickly can cause cracking or surface flaking—keep the concrete moist during early curing if it will be extremely hot and dry. Improperly compacted sub-base can lead to settling. Not installing control joints can result in large cracks. Always check weather and have a backup plan if rain or extreme heat is expected.
