Introduction
Bull floating uses a wide, rigid tool to flatten and level fresh concrete quickly while magnesium floating uses a lighter, textured board to work the surface finer; choose the tool that matches where you are in the finishing sequence and the look you want. In practice that means use a bull float early to get rid of high spots and push bleed water down, and switch to a magnesium float later when the slab has stiffened enough to refine texture and close the surface. Check product instructions and local rules for timing and compatibility with your mix or finish system.
This is a hands-on trade decision more than a theoretical one—bull floats move material and set the slab plane, magnesium brings up paste and lets you shape the final surface. For a DIY job plan to use both in sequence or pick the one that fits your desired finish and the slab’s set time, and when in doubt wait a bit and test a small area. If you need specifics on timing, tool sizes, or blade types, check the tool manufacturer and mortar/concrete guidelines before you start.
Key takeaways
- Choose bull float for larger, open pours and coarser finishes.
- Magnesium floats yield smoother surfaces when the substrate is near final height.
- Delay magnesium use until bleed water is absorbed and joint edges are set.
- Keep blades clean and edges lifted to avoid tearing freshly floated concrete.
- Wear eye protection and a dust mask during finishing to manage dust.
- Match tool choice to finish type, weather, and project constraints for best results.
Table of Contents
- Introduction
- Key takeaways
- Quick Comparison Overview
- Substrate and Timing: When to Use Each Tool
- Finish Outcomes and Visual Checkpoints
- Tools and Materials Checklist
- Step-by-Step Technique and Best Practices
- Common Problems and Troubleshooting
- Match the Float to the Finish Type and Project Constraints
- Safety, Efficiency, and Cost Considerations
- Conclusion
- FAQ
Quick Comparison Overview
A bull float is a long-handled tool used early to level and embed aggregate, while a magnesium float is shorter and used later to refine the surface and close the texture. This overview frames intended timing, how each affects surface appearance, and the common jobsite roles for both tools.
Think of the bull float as a coarse planer and the magnesium as a finer scraper that brings the slab toward its final look. Read product labels or manufacturer instructions for any tool-specific guidance you must follow on your project.
What a bull float does
A bull float is your first line of defense against an uneven concrete surface. It’s used early in the finishing process, right after leveling and before any other tools come into play.
The bull float is designed to close large fines – those tiny voids that can trap water or air. By pushing a thin layer of cement paste to the surface, it creates a smooth, level base for your finish.
Think of it like laying down a foundation for your final finish. You wouldn’t want to paint a wall with visible cracks, would you? The same goes for concrete – you need that initial leveling and smoothing before you can move on to the next steps.
What a magnesium float does
A magnesium float, also known as a ‘screed’ float, is your next step in refining that concrete surface. It’s used after the bull float and before any final finishing or brooming.
The magnesium float has a slightly different design – it’s lighter and more flexible than the bull float. This allows it to smooth out those smaller imperfections left behind by the bull float, creating an even smoother surface.
It also helps to bring up any remaining cement paste from below, further closing those tiny voids. This step is crucial for preparing your concrete for its final finish – whether that’s a broom finish, stamped pattern, or something else.
Substrate and Timing: When to Use Each Tool
Use a bull float when the concrete has set enough to support the tool without digging but still has working moisture or bleed water present; it pushes aggregate down and brings cement paste up. Switch to a magnesium float after bleed water dissipates and the surface firms to the point where you can work it without dislodging aggregate.
If you’re unsure about the slab’s readiness, check the surface for standing water and test for surface firmness with a fingertip or heel—refer to product data sheets or contractor guidance for timing cues. Sometimes both tools are used sequentially: bull float first, magnesium float to refine before final finishing.
Using a bull float on fresh placement
The best time to grab your bull float is when the concrete has just been poured and is still wet. But don’t rush in too early.
Wait for these signs:
- Bleed water starts appearing on the surface.
- The concrete is firm enough that it doesn’t leave footprints or sag under your weight.
Now, gently pull the float across the slab. You’re not scrubbing, you’re leveling and consolidating. Too much work can cause segregation.
Using a magnesium float at the right moment
The magnesium float comes into play later, when the concrete has started to set but is still soft. You’ll know it’s time when:
- The bleed water has disappeared.
- The surface is firm but not yet hard.
Now, lightly drag the float across the slab. You’re smoothing out any imperfections and bringing up a fine, smooth finish. But be careful – too much work can cause crazing or leave marks.
Finish Outcomes and Visual Checkpoints
Bull floating leaves a flatter, open-pore surface that’s good for initial leveling, while magnesium floating produces a tighter, smoother surface ready for brooming, troweling, or sealing. Expect different visual cues: bull float marks are broader and less defined; magnesium marks are finer and indicate paste has been brought up.
Look for disappearance of bleed water, reduction of visible aggregate, and uniform sheen as checkpoints before changing tools or proceeding to the next finish. When in doubt about readiness for the next step, verify with the manufacturer instructions or established jobsite tests rather than guessing.
Smoothness, Sheen, and Texture Differences
Before you move on to polishing or applying coatings, check these points to ensure your surface is ready.
- Bull Float: Leaves a slightly textured surface with a matte sheen. Ideal for rough-in work and when using broadcast toppings.
- Magnesium Float: Produces a smoother, more refined finish with a subtle gloss. Suitable for final finishes and polished surfaces.
- Bull Float – Texture: Should have small, evenly spaced ridges. Too many or too deep? You might need to re-float.
- Magnesium Float – Smoothness: Expect a mostly smooth surface with minimal imperfections. Any major blemishes? Re-check your technique.
Quick rule: Bull float for rough-ins, magnesium float for final finishes.
Preparing for Toppings, Sealers, or Coatings
Before applying any toppings or sealers, ensure your surface is properly prepared with these checks.
- Bull Float – Flatness: Check for low spots or waves. These can affect topping adhesion and appearance.
- Magnesium Float – Porosity: Ensure the surface is not too porous. A water drop should bead up, not soak in.
- Both Floats – Laitance Removal: Confirm all laitance (cement-rich layer) has been removed. It can hinder adhesion and cause delamination.
Quick rule: Flat, non-porous surfaces with no laitance ensure better adhesion for toppings and sealers.
Tools and Materials Checklist
Have on site: a bull float with appropriate handle/extension, at least one magnesium float, a straightedge or screed, push broom, finishing trowel(s), and a float pan or edging tool as needed. Include consumables like jointing tools, mixing water control items, and replacement float blades or pads if the design allows.
Match handles to tool length and your crew’s reach—telescoping or sectional handles are common; confirm load limits and secure connections per manufacturer instructions. If you need specific accessory specs, check product labels or supplier sheets for compatibility and safe use.
Essential tools and sizing options
Before you start mixing concrete, make sure you have the right tools. Use this checklist to ensure you’re well-equipped for a smooth pour.
- Floats: Check size (6″ – 12″) based on slab thickness. Too small and you won’t cover the area; too large and it’s unwieldy.
- Handles: Ensure they’re secure and comfortable for your grip. Try them out before starting work.
- Finishing trowels (square shovels): Choose sizes from 12″ to 36″ based on slab size. Check they’re in good condition with no bends or cracks.
- Screeds: Length should match the width of your slab. Check for straightness and secure handle attachment.
- Concrete rake (garden rake): A sturdy one is needed to spread concrete evenly. Check teeth are intact and not bent.
- Wheelbarrow: Size depends on job access. Check it’s stable, has good wheels for your site conditions, and can handle the load.
- Concrete mixer (optional): If using, check size matches batch size (e.g., 3 cu. ft. for a small patio). Ensure it’s in working order with no leaks or cracks.
- Tape measure: Essential for checking dimensions and ensuring tools are the right size.
- Level: Check it’s accurate (bubble level) and long enough to span your slab. A 4′ – 8′ level is usually sufficient.
Quick rule: Always check tools before starting work. Damaged or wrong-sized tools can lead to poor finishes, rework, and wasted concrete.
Material specs and standards explained
Before you start mixing concrete, use this checklist to ensure your materials meet the required specs and standards. This will help you achieve a durable, long-lasting finish.
- Float Material: Check manufacturer recommendations for the best float material (wood, magnesium, or steel) based on your desired finish. Confirm it’s in good condition with no warping or cracks.
- Handle System: Ensure your handle system (t-bar, broomstick, or other) is compatible with your float and allows for easy maneuvering. Check that it’s securely attached to the float.
- Concrete Mix Design: Verify the mix design (water-cement ratio, aggregate size, etc.) adheres to local building codes and industry standards like ASTM C94 or ACI 301. Check with your concrete supplier if unsure.
- Cement Type: Confirm you’re using the correct type of cement (Type I, II, III, etc.) for your project’s requirements. Check the bag for the type and manufacturing date.
- Admixtures: If using admixtures (accelerators, retarders, air-entraining agents), ensure they’re compatible with your cement type and mix design. Follow manufacturer guidelines for dosage rates.
- Aggregate Size: Check the nominal maximum size of your aggregate (stone) doesn’t exceed 3/4″ for most residential slabs. Ensure it’s clean, dry, and free of excessive fines or coatings.
- Water Quality: Verify your water source is clean and free from contaminants that could affect concrete performance. Check local water quality reports if needed.
- Finish-Surface Compatibility: Ensure the desired finish (smooth, broomed, exposed aggregate, etc.) is compatible with your chosen concrete mix design and placement method.
Quick rule: Always check materials against manufacturer recommendations and industry standards to avoid costly rework and ensure a quality finished product.
Step-by-Step Technique and Best Practices
Start with screeding, then immediately follow with the bull float using continuous, slightly overlapping passes to level and embed aggregate without gouging. After bleed water clears and the slab firms, switch to the magnesium float using shorter, overlapping circular or sweeping strokes to refine texture and close surface pores.
Maintain flat tool faces, keep a light trailing edge on passes, and avoid excessive pressure that can pull paste or create ripples; practice stroke patterns on a small area if uncertain. If manufacturer guidance differs, follow their recommended technique and timing for the specific tools you’re using.
Step-by-Step Process
The following steps guide you through the process of using bull and magnesium floats to achieve a smooth, consistent finish on your concrete slab.
- **Preparation:**
– Ensure safety: wear appropriate gear (gloves, boots).
– Check weather: avoid floating in extreme temperatures or humidity.
– Inspect the slab: remove any debris or contamination. - **Bull Float:**
– Start at the farthest point from where you’ll exit.
– Use long, smooth strokes, overlapping about 50%.
– Lift and turn the float to avoid gouges. Check for uniform consolidation. - **Magnesium Float:**
– Once bleed water has dissipated (1-2 hours), start floating.
– Begin at the same farthest point.
– Use short, overlapping strokes (about 75%).
– Apply even pressure; check for sheen and smoothness. - **Transition:**
– Switch to magnesium float when bull float starts to leave marks.
– Work in a ‘Z’ or ‘S’ pattern to cover the entire slab efficiently. - **Final Checks & Cleanup:**
– Inspect for any missed spots or imperfections.
– Allow the slab to cure according to manufacturer’s guidelines.
– Clean and store your tools properly.
Preparing the Slab Before Floating
Proper preparation ensures a smooth floating process. Here are key steps to prep your slab:
Initial Screeding: Ensure the concrete is level and free of high or low spots.
**Remove Puddles:** Use a rake or shovel to eliminate any standing water or muddy areas.
**Verify Bleed Water:** Wait for bleed water (moisture rising to the surface) to dissipate. This usually takes 1-2 hours but can vary based on temperature and humidity.
Proper Float Strokes and Overlap
Efficient floating requires consistent strokes and overlap to avoid ridges or gouges:
**Stroke Direction:**
– For bull float: long, smooth strokes (about 6-8 feet).
– For magnesium float: short, overlapping strokes (about 2-4 feet).
**Overlap:**
– Bull float: overlap about 50% to ensure full coverage.
– Magnesium float: overlap about 75% for a smooth, consistent finish.
**Pressure:**
– Apply even pressure throughout the stroke.
– Lift and turn floats at the end of each stroke to avoid gouges.
Sequence: Bull Then Magnesium vs Magnesium Only
The sequence depends on your desired finish and slab condition:
**Bull then Magnesium:**
– Use this sequence for a smooth, high-sheen finish.
– Bull float first to consolidate and remove large imperfections.
– Follow up with magnesium float for final smoothing.
**Magnesium Only:**
– This is sufficient when you want a matte finish or the slab has minimal imperfections.
– Start floating once bleed water has dissipated.
– Use short, overlapping strokes for a consistent, smooth surface.
Common Problems and Troubleshooting
Overworking with a bull float can push too much paste and create weak surface laitance, while premature magnesium floating can tear aggregate and leave gouges. Watch for common defects: stringing, pull-up of coarse aggregate, trowel burn, or uneven sheen that indicate timing or pressure issues.
Diagnose by checking surface moisture, firmness, and the type of marks left by the tool; correct by reworking with the appropriate float or allowing the slab to firm or dry further before retrying. If a repair requires materials or steps beyond basic floating, consult product technical literature or a pro for the safest approach.
Overworking and creating surface defects
Using the float too long after initial set can lead to problems. You’ll see:
- Scumming: A hazy, whitish layer on the surface.
- Weakened surface: The concrete becomes soft and easily damaged.
Remedy: Stop floating immediately if you notice these signs. Let it set further before trying again. Avoid in future: Keep an eye on your pour’s progress. Float as soon as the bleed water disappears, but don’t overdo it.
Underworked areas and uneven texture
Incomplete floating leaves you with an inconsistent finish. Look for:
- Uneven sheen: Some spots look dull, others glossy.
- Texture variations: Bumpy or rough patches.
Fixes: Re-float underworked zones as soon as possible. For small areas, use a trowel to smooth out texture. Prevent in future: Be thorough and patient during the floating process. Ensure you’ve covered every inch of the slab.
Environmental and mix-related issues
Weather conditions and mix proportions can impact your float job:
- Temperature: Too hot, and the concrete sets too fast. Too cold, and it sets too slow. Adjust your timing accordingly.
- Wind: Strong winds dry out the surface quickly, causing an inconsistent finish. Protect your pour from wind if possible.
- Water content: Too much water in the mix makes for a weak, soft concrete. Too little, and it’s hard to work with. Ensure your mix is properly proportioned.
Adjustments on site: Monitor conditions closely. If needed, adjust your float timing, protect from wind, or request a remix of the concrete.
Match the Float to the Finish Type and Project Constraints
For broom finishes, a magnesium float just before brooming usually provides the right texture; for heavy textured or exposed aggregate, a bull float may be used early and specialized tools later. Polished or sealed finishes often need the smoother surface that magnesium floating yields prior to subsequent polishing steps or sealer application.
Factor in slab size and crew—large pours may favor extended bull floating to speed initial leveling, while small decorative slabs may allow more careful magnesium work. Check product data sheets and local best practices for any finish-specific requirements or constraints you must meet.
Decorative and Polished Concrete Considerations
When you’re after a high-gloss, decorative finish like polished concrete, the initial floating stage is crucial. A bull float gives a coarser finish, which can make polishing prep more challenging. It’s best to use a magnesium float for these jobs.
Magnesium floats leave a finer, smoother surface right off the bat. This makes it easier to achieve that mirror-like shine you’re after with minimal additional effort.
Tip: If you’re planning on stamping or applying decorative treatments, a magnesium float’s smooth finish ensures better adhesion and clearer patterns.
Exterior, Broom, and Non-Slip Finishes
For exterior slabs or surfaces that need a textured, non-slip finish like a broom finish, a magnesium float isn’t your best bet. It leaves too smooth a surface for effective brooming.
A bull float, on the other hand, creates a rougher surface perfect for brooming. It helps the broom’s bristles grip and leave their mark, creating that textured, slip-resistant surface you need.
For non-slip surfaces, consider using a bull float followed by a broom finish. This combination provides excellent traction, making it ideal for driveways, walkways, and pool decks.
Large Pours, Hard-to-Reach Areas, and Repairs
When you’re dealing with large slabs or hard-to-reach areas, a bull float might be your best friend. Its larger size and sturdier construction make it easier to handle in these situations.
For repairs, a bull float is often the way to go as well. It can easily smooth out the new concrete to match the existing surface, helping to blend the repair seamlessly.
Tip: In tight spaces or for smaller repairs, a magnesium float might be more practical due to its lighter weight and maneuverability. But for most large pours and repairs, the bull float is your best choice.
Safety, Efficiency, and Cost Considerations
Ergonomics matter: bull floats require handling longer reach and can be more physically demanding, while magnesium floats are lighter but require closer attention and often more passes. Plan workflow so one crew handles initial screed and bull floating while another follows with magnesium and finishing to save time and reduce fatigue.
Compare effort versus finish need—using both tools increases labor but improves surface control, while using only one can cut time at the cost of finish quality. When selecting tools or renting gear, consult supplier specifications and local rules to ensure you meet safety and performance expectations for your job.
Ergonomics and operator safety
When it comes to floating, safety and comfort are key. Here’s how to keep your crew safe and reduce fatigue:
PPE: Always wear proper personal protective equipment – gloves, safety glasses, and steel-toed boots.
Handling: Bull floats can be heavy. Use both hands for better control. For long-handle floats, maintain a comfortable posture with your back straight and knees bent.
Rest breaks: Floating is physically demanding. Schedule regular rest breaks to prevent fatigue and reduce the risk of injury.
Labor, timing, and project scheduling
The choice of float can impact your labor needs and schedule. Here’s how:
Crew size: Bull floats require more manpower due to their size and weight. Magnesium floats are lighter and can be operated by fewer people.
Timing windows: Bull floating takes longer than magnesium floating due to its larger surface area. Plan your schedule accordingly, especially in hot weather where quick finishing is crucial.
Sequencing with other trades: Coordinate with other trades like rebar installers and formwork teams. Bull floats may require more space for operation, while magnesium floats can be used in tighter areas.
When to hire a pro vs DIY
Knowing when to DIY and when to hire a professional can save you time, money, and stress. Here’s some guidance:
DIY: For small projects like patios or walkways, and if you have basic concrete experience, go ahead and DIY. It’s a great way to learn and save.
Hire a pro: For large pours, complex designs, or critical surfaces like floors in high-end homes, consider hiring a professional. They have the expertise, equipment, and insurance to handle these projects safely and efficiently.
Consult first: If you’re unsure, consult with a local pro. They can provide advice tailored to your specific project and conditions.
Conclusion
Choosing the right float and timing matters for a durable, smooth finish that lasts. Stay safe, test your approach first, and don’t push past the limits of the surface you’re working on.
Start by confirming the substrate is clean and cured, then decide which tool fits your finish and timing window, lay out your plan, and test a small patch before you commit. Float in light, even passes, keep the blade flat, wipe or knock down gaps as you go, and stop as soon as you see a consistent surface. Have your materials and tools ready, work in good light, and keep edges and corners clean as you finish.
Avoid common mistakes like using the wrong float for the finish, overworking the surface or chasing a gloss that isn’t achievable with the chosen tool, and skipping a clean, dry test area. Safety first means wearing a dust mask when sanding, keeping kids and pets away, and never leaning on wet or unstable surfaces. If you’re dealing with a large area, exposed moisture, or suspect substrate failure, don’t force it—call a professional. When you handle the basics carefully, you’ll get a reliable finish and save time and money in the long run. Stay steady, stay sharp, and finish strong.
FAQ
When should I use a bull float versus a magnesium float on fresh concrete?
Use a bull float to level and push down high spots on a larger area and to bring up the cream as you strike the surface. Switch to a magnesium float for a finer finish and to wick away excess water or laitance without marring the surface. Check the product label and manufacturer instructions for guidance on your mix and finish timing.
How do I know when the surface is ready for finishing after using either tool?
Wait until the surface loses the glossy sheen and the water sheen disappears, then test with a light drag of the float or a broom in a small area. If the surface still tracks easily or shows standout aggregate, give it a bit more set time. Always consult the concrete’s curing information and local guidelines for timing hints.
What are the most common finish issues and how can I prevent them?
Problems like pinholes, grind marks, or a rough skin come from floating too early or with the wrong tool. Keep the float moving with consistent pressure and avoid overworking the same spot. If in doubt, re-check the manufacturer instructions and adjust your timing and tooling accordingly.
How should I maintain and clean my floats to keep finishes smooth?
Rinse and wipe the floats after use to remove concrete slurry and dust. Dry them before storage to prevent rust or corrosion on metal parts. Follow the tool maker’s care recommendations and replace worn edges or blades as needed.