Installing furring strips on a concrete block wall creates a stable, flat surface for insulation, drywall, or siding. This approach is common in basement renovations, commercial buildings, and exterior weather barrier projects.
The process relies on proper fasteners, surface prep, and moisture control to ensure long lasting performance. Following a clear sequence reduces rework and keeps the wall assembly both code compliant and durable.
| Method | Best Use Case | Typical Fastener | Estimated Hold Strength |
|---|---|---|---|
| Epoxy Anchored Bolts | Heavy loads, structural upgrades | Epoxy anchor bolts | High, up to shear rating of epoxy |
| Plastic Expansion Anchors | Light to medium fixtures in cured block | Screws with nylon or resin sleeve | Moderate, depends on edge distance |
| Concrete Screw Anchors | Quick install, moderate loads | Tapcon or similar self drilling screw | High withdrawal resistance |
| Supplementary support, uneven backs | Mechanical fasteners plus structural adhesive | Combined bond for shear and pull off |
Preparing the Concrete Block Surface
Thorough cleaning is essential before any furring strip attachment. Remove dust, oil, and previous coatings with a stiff brush and vacuum or pressure washer, allowing the wall to dry fully.
Check for cracks, spalling, or significant moisture issues and address them first. Use a moisture meter to confirm readings are within manufacturer limits for adhesives or fasteners, preventing premature failures.
Selecting Materials and Fasteners
Choose furring strips made from pressure treated wood, metal studs, or fiber cement boards depending on the application and exposure. Match strip dimensions to the required air gap and load requirements.
Select fasteners based on wall thickness, strip thickness, and load, with sleeve anchors, concrete screws, or epoxy bolts commonly specified. Verify that fastener length provides ample embedment into the solid concrete behind the block.
Layout and Fastener Pattern Design
Snap a level reference line along the planned top of the furring strip, then mark vertical fastener locations at recommended spacing, usually 12 to 16 inches on center for structural work.
Use a hammer drill with a masonry bit slightly smaller than the anchor body to place holes. Maintain consistent embedment depth, and stagger holes between rows to avoid weakening the wall line.
Using a Template for Repetitive Patterns
Create a layout template from scrap furring material to transfer fastener locations quickly across long runs. This reduces measurement errors and keeps the installation aligned.
Attachment Methods and Best Practices
For adhesive only, apply a high bond mortar or structural adhesive rated for concrete, then press the furring strip firmly into place using temporary supports until set.
For combined mechanical and adhesive methods, drill pilot holes, set anchors, apply adhesive to the back of the strip, and tighten fasteners in a staggered sequence to distribute stress evenly.
Sequencing for Long Runs
Install intermediate supports or shims every few feet on long runs to maintain level and prevent bowing. Adjust each fastener gently to keep the furring plane true without shifting adjacent sections.
Moisture and Insulation Integration
Add a drainage plane or capillary break between the furring and the block wall to manage incidental moisture. This air gap also allows cavity insulation to be placed without direct contact with the concrete.
Verify that furring strips are deep enough to accommodate insulation plus a finished surface layer. Use continuous insulation strategies where required to prevent thermal bridging through the masonry.
Code Compliance and Quality Checks
Review local building codes for minimum embedment depth, fastener spacing, and fire rating requirements, especially when furring strips are used in assemblies shared with occupied spaces.
Conduct a pull test or embedment verification on a small area before full installation, confirming that the selected fasteners meet the specified withdrawal values for the substrate.
- Confirm moisture levels and address spalling or salt migration before attachment.
- Select furring materials compatible with the wall assembly and exposure conditions.
- Use a level and layout template for consistent, aligned fastener placement.
- Employ proper fastener length and embedment depth for the concrete hardness.
- Install a drainage plane or capillary break when moisture is present.
- Stagger fastener rows to avoid creating continuous vertical mortar joints.
- Verify spacing patterns against the expected loads from insulation and finishes.
- Document anchor type, embedment depth, and spacing for future reference.
FAQ
Reader questions
Can I use plastic anchors in older, crumbly concrete block?
Plastic anchors rely on solid concrete for hold. In crumbly or deteriorated block, use epoxy anchor rods that penetrate to sound material or consider through bolts with plates on both sides.
How far from the edge of the block should furring strips be placed?
Maintain at least one and a half times the embedment distance between any fastener and the edge of the block to prevent cracking and pullout.
Is it acceptable to attach furring strips directly without a drainage plane in a damp basement?
In consistently damp conditions, a drainage plane or capillary break is strongly recommended. Skipping this layer can trap moisture and promote mold growth within the cavity.
What fastener spacing is typical for supporting horizontal furring strips bearing light drywall?
Twelve inch on center fasteners along the vertical studs and at slab or floor attachments usually suffice for light duty applications, while heavier loads require closer spacing and larger anchors.