What are Screw Anchors?
Screw anchors, also called masonry screws and anchor screws, cut their own threads into a predrilled hole in concrete, brick, or block. They install quickly with a driver, provide reliable holding power, and can be removed without leaving bulky hardware in the hole.
What are Concrete Screws?
Concrete screws are the thread-cutting subset of screw anchors designed for concrete and dense masonry. By forming mating threads in the base material, they create a strong, one piece connection without sleeves or wedges.
What are screw anchors used for?
- Mounting rails, brackets, machinery bases, conduit, and fixtures to concrete and masonry
- One side installs where access behind the fixture is limited
- Projects that may need removal or repositioning during commissioning
- Light to medium duty structural attachments when used as specified
Common types of screw anchors
- Hex washer head for strong drive engagement and clamping
- Flat head countersunk for a flush finish under plates and trim
- Coated carbon steel finishes for dry or mildly damp interiors
- Stainless steel options where added corrosion resistance is required
How to size Concrete Screws (inch and metric)
- Select diameter by load and fixture hole, for example 3/16 in, 1/4 in, or M6, M8
- Choose length to cover fixture thickness plus the minimum embedment for the screw size
- Drill the specified pilot size and depth so threads form correctly in the base material
- Maintain spacing and edge distance to protect the substrate from cracking or breakout
Materials and finishes
Carbon steel with protective coating
Economical and widely used. Finishes such as zinc or specialized coatings provide rust resistance in dry or mildly damp locations.
Stainless steel
Chosen for corrosive or washdown environments. 410 stainless balances strength and corrosion performance, while 304 or 316 may be used where conditions are more aggressive.
Installation tips for concrete screws
- Drill a straight pilot hole with the correct bit and clean out dust by brushing and blowing
- Drive with steady pressure and avoid over torque to prevent thread stripping
- For countersunk heads, match the countersink in the fixture so the head seats evenly
- If removal is needed, back the screw out and inspect threads before any reuse allowed by the spec
Where do screw anchors work best?
- Solid concrete in dry interiors or protected exteriors
- Brick and block when drilled into the solid portion of the unit
- Temporary or adjustable mounts that may be moved during setup
Screw anchors vs wedge and sleeve anchors
Screw anchors cut threads in the base material for rapid installation and easy removal. Wedge and sleeve anchors use expansion components and are preferred for consistently higher loads or where a flush drop in or sleeve is specified.
FAQs about Screw Anchors
Answers to common search questions on choosing, sizing, and installing screw anchors and concrete screws.
- What drill bit size should I use for concrete screws?
Use the pilot size specified for the screw diameter. Correct bit size is critical for thread formation and holding power.
- How deep should I drill the hole?
Drill deeper than the required embedment to allow for dust and full thread engagement. Follow the embedment guidance for your screw size.
- Can screw anchors be used in brick or block?
Yes, when drilled in the solid portion of the unit. Avoid thin webs or voids that reduce engagement.
- Are concrete screws removable?
Yes. Back them out with the driver. Reuse depends on condition and the application’s requirements.
- How close to an edge can I install a screw anchor?
Keep minimum edge distance and spacing to prevent cracking or breakout. Check values for your size and base material.
- When should I choose hex head versus flat head?
Hex washer heads provide strong drive and clamping. Flat heads give a flush finish under plates or trim.
- Do screw anchors require hole cleaning?
Yes. Brush and blow out dust before installation. Debris reduces thread formation and capacity.
- What is the minimum embedment for concrete screws?
Each size has a minimum embedment for rated performance. Choose a length that meets it with your fixture thickness.
- Do screw anchors work in cracked concrete?
Some products are qualified for cracked concrete and some are not. Verify the rating and follow installation instructions.
- What if the hole is oversized?
Do not use the anchor. Drill a new properly sized hole to ensure holding power.