Brick is one of the best wall materials for mounting solar lights, and also one of the most misunderstood. The misunderstanding comes from a single question that installers get wrong more often than they get right. Do you drill into the brick, or do you drill into the mortar?
The answer, in almost every case, is the mortar. Mortar joints are softer than brick, easier to drill, easier to patch if you make a mistake, and structurally less important than the brick itself. Drilling into the face of a brick risks cracking the brick, which is permanent and visible. Drilling into the mortar risks nothing that cannot be easily repaired with a tube of mortar patch.
I have mounted dozens of solar fixtures on brick walls, chimneys, and brick columns over the years. Every installer I know who works with brick regularly follows the same rule. Drill the mortar, not the brick. This guide covers why, how, and what to do when the mortar is not where you need it to be.
Understanding Brick Wall Anatomy
A brick wall is a system of two materials working together. The bricks provide compressive strength and weather resistance. The mortar between them bonds the bricks together and distributes loads. Understanding how these two materials interact determines where and how you should mount fixtures.
Standard modular bricks measure 7-5/8 inches long, 3-5/8 inches wide, and 2-1/4 inches tall. With a standard 3/8 inch mortar joint, the visible face of each brick is about 7-1/4 by 2-1/4 inches. The mortar joints run horizontally (bed joints) and vertically (head joints) between the bricks. The bed joints are typically 3/8 inch thick, which is enough to accommodate a small anchor without damaging the surrounding brick.
The strength of a brick wall comes primarily from the bricks themselves, not the mortar. Mortar is intentionally softer than brick so that it acts as a sacrificial material. When the wall moves, expands, or contracts due to temperature changes, the mortar joints absorb the stress rather than the bricks. This is why old brick walls often have crumbling mortar but intact bricks. The mortar gave its life to protect the bricks.
This sacrificial quality is exactly what makes mortar the ideal mounting point. When you drill into mortar, you are drilling into a material that is designed to be replaced. If you later remove the fixture, you fill the hole with new mortar and the wall is restored. If you drill into a brick and crack it, the brick cannot be replaced without removing and resetting the entire brick, which is a masonry project that costs more than the light fixture.
There are two types of mortar joints. Running bond, the most common pattern, has bricks offset by half their length, so the vertical joints are staggered. Stack bond has bricks directly on top of each other, with vertical joints aligned. Running bond provides more mortar joint options for mounting, because there are vertical joints at every brick position. Stack bond limits your vertical joint options to every other brick.
The age of the mortar matters. Older homes (pre-1950) typically have lime mortar, which is soft, slightly flexible, and very easy to drill. Modern homes use Portland cement mortar, which is harder and more brittle. Lime mortar drills like chalk. Portland cement mortar drills like… well, cement. You can tell the difference by pressing a screwdriver into a mortar joint. If it leaves a mark, it is lime mortar. If it does not, it is Portland cement.
Tools and Materials List
Having the right tools before you start saves multiple trips to the hardware store and prevents the temptation to substitute inferior tools mid-project. Here is the complete list for a brick installation.
- Hammer drill. A standard drill will work in soft lime mortar but will struggle in Portland cement mortar. A hammer drill with adjustable speed is the right tool for all mortar types.
- Carbide-tipped masonry drill bits. You need the size specified by your anchor manufacturer, typically 3/16 or 1/4 inch. Buy two bits. Masonry bits dull quickly in brick mortar, and a dull bit increases drilling time and the risk of cracking.
- Masonry anchors. Plastic expansion anchors for light fixtures, or lead anchors for heavier fixtures. Match the anchor size to the screw size that comes with your mounting bracket.
- Masonry screws (optional, as an alternative to anchors). 1/4 inch diameter, in lengths from 1.75 to 2.75 inches. These thread directly into the mortar without a separate anchor.
- Mortar patch compound. For filling old holes if you are replacing or relocating fixtures, and for any mistakes. Buy a small tub of pre-mixed mortar patch in a color close to your existing mortar.
- Silicone sealant. For sealing around the mounting bracket to prevent water intrusion. Choose a color that matches your mortar or use clear.
- Level. At least 12 inches long, for positioning the bracket straight.
- Tape measure. For spacing multiple fixtures evenly.
- Pencil or chalk marker. For marking drill locations. Do not use permanent markers, which can stain brick.
- Shop vacuum with brush attachment. For cleaning mortar dust as you drill, so it does not stain the brick face.
- Wire brush. For cleaning the mortar joint before drilling, to remove loose material.
- Safety glasses and dust mask. Mortar dust is alkaline and irritating.
- Putty knife. For applying mortar patch and for smoothing sealant.
- Cable clips with masonry nails. For securing any cables along the brick wall if your fixture uses a remote panel.
Locating and Marking Mortar Lines
Finding the mortar joints is straightforward, but finding the right mortar joint for your fixture requires a bit more thought. The joint needs to be at the right height, in the right horizontal position, and in a section of mortar that is solid and intact.
Start by holding the fixture (or its mounting bracket) against the wall at the desired height. Look at where the mounting holes in the bracket fall relative to the mortar joints. Ideally, every mounting hole falls on a horizontal bed joint, which runs continuously across the wall and provides the most material for anchoring. If a mounting hole falls on a brick face, adjust the bracket position up or down until it aligns with a mortar joint.
For brackets with two mounting holes, you want both holes on the same horizontal bed joint, or on two bed joints spaced the right distance apart. This is usually possible with minor adjustments. For brackets with three or four holes, you may need to use a combination of bed joints and head joints (the vertical mortar lines between bricks).
Check the condition of the mortar at your chosen location. Use the wire brush to clean the joint and look for any crumbling, cracks, or gaps. If the mortar is crumbling or has gaps deeper than 1/4 inch, choose a different location. Loose mortar will not hold an anchor.
For running bond walls, the horizontal bed joints are continuous and run the full width of the wall. This gives you the most flexibility for horizontal positioning. The vertical head joints are only 3-1/2 inches long (the width of one brick), so they limit where you can place a vertically aligned anchor.
Mark the exact drill point on the mortar joint with a pencil. Make the mark in the center of the joint, not at the edge where mortar meets brick. Drilling at the edge risks damaging the brick face. Center the hole in the mortar for maximum material on all sides.
Measure the distance between multiple fixtures to ensure they are evenly spaced. Use a tape measure and mark each location before drilling anything. It is much easier to adjust pencil marks than to fill drill holes and start over.
Drilling Technique for Mortar Joints
Drilling into mortar is easier than drilling into brick, but it still requires care to avoid damaging the surrounding bricks. The goal is a clean, straight hole that is the right depth and does not crack the mortar or spall the brick edges.
- Clean the mortar joint at the drill location with a wire brush. Remove all loose material and dust. This gives you a clean surface to start the drill bit and prevents loose material from contaminating the hole.
- Mark the drill point with a pencil in the center of the mortar joint. Place a piece of painters tape over the mark and re-mark on the tape. The tape prevents the drill bit from wandering on the mortar surface.
- Set your hammer drill to the lowest speed with hammer action off. Press the bit against the tape and start drilling slowly to create a starter hole. This prevents the bit from skating across the mortar, which can scratch the adjacent brick.
- Once the starter hole is established (about 1/8 inch deep), turn on the hammer action and increase to medium speed. Let the hammer action do the work. Do not press hard. The hammer action chips the mortar away. Excessive pressure causes the bit to grab, which can crack the mortar joint.
- Keep the bit perfectly perpendicular to the wall. Any angle causes the bit to bind and can enlarge the hole on one side, which weakens the anchor grip.
- Drill to the depth required by your anchor. This is typically 1 to 1.5 inches for plastic anchors in mortar. Use a piece of tape on the drill bit as a depth gauge, or count the turns if you know the thread pitch.
- Pull the bit out slowly while it is still spinning. This clears the hole of dust and debris. Do not pull the bit out while it is stopped, which can leave debris packed in the bottom of the hole.
- Clean the hole by blowing it out with compressed air or vacuuming with a narrow nozzle. The hole must be clean for the anchor to grip properly. Dust and debris in the hole are the most common cause of anchor failure.
- Check the hole for cracks in the surrounding mortar. Small hairline cracks are normal and do not affect anchor performance. Larger cracks mean the mortar is deteriorating, and you should choose a different location or consider using epoxy to set the anchor.
The drill bit size must match the anchor. For plastic expansion anchors, drill 1/8 inch smaller than the anchor diameter. The anchor is then tapped into the slightly undersized hole, where it grips the mortar walls. For masonry screws, drill exactly the diameter specified by the screw manufacturer. Masonry screws cut their own threads and require a precise hole size.
Do not use a standard twist drill bit for mortar. The carbide tip on a masonry bit is what chips the mortar away. A twist bit will spin in the hole without cutting, generating heat and eventually dulling to the point where it cannot drill at all.
Installing Anchors and Mounting Brackets
Once you have clean, correctly sized holes in the mortar, the next step is installing the anchors and mounting the bracket. This is the straightforward part, but attention to detail here determines whether the fixture stays up for years or falls down in the first windstorm.
- Push the plastic anchor into the hole by hand. It should be snug. If it slides in easily, the hole is too large and the anchor will not grip. If it will not go in at all, the hole is too small. Remove the anchor and redrill with the next size up bit.
- Tap the anchor gently with a hammer until it is flush with the mortar surface. Do not drive it below the surface. An anchor that is recessed into the mortar has less grip and creates a pocket that collects water. An anchor that sticks out prevents the bracket from sitting flat.
- Position the mounting bracket over the anchors. Insert the mounting screws through the bracket holes and into the anchors.
- Drive the screws with a screwdriver or low-speed drill. Tighten until the bracket is firm against the brick. Do not overtighten. Overtightening strips the anchor, which loses all holding power and requires removal and replacement.
- For masonry screws (without separate anchors), drive the screw directly into the cleaned hole using a hex head bit. Drive slowly and let the screw cut its threads into the mortar. Stop when the bracket is tight. Masonry screws have a specific torque and will snap if overtightened.
- Check the bracket with a level. If it is not level, loosen the screws slightly, adjust, and retighten. Do not remove and reinstall the anchors, which weakens the mortar grip.
- Apply a bead of silicone sealant around the top and sides of the bracket where it meets the brick. This prevents water from running behind the bracket and into the mortar joints. Do not seal the bottom edge, which allows any water that does get behind the bracket to drain out.
- Smooth the sealant with a wet finger or putty knife for a clean appearance. Let it cure for 24 hours before attaching the light fixture.
- Attach the solar light fixture to the mounting bracket according to the manufacturer’s instructions. Most fixtures clip or screw onto the bracket. Do not overtighten any screws on the fixture itself, which can crack the plastic housing.
- If the fixture uses a remote solar panel, route the cable along the mortar joints using cable clips with masonry nails. Drive the nails into the mortar, not the brick. Space clips every 12 inches to support the cable and prevent sagging. Seal each nail hole with a dab of silicone.
Avoiding Damage to Brick Faces
The most important rule of brick installation is to avoid damaging the brick faces. Bricks are the visible, structural element of the wall, and any damage to them is permanent and obvious. Mortar can be patched and repaired invisibly. Brick faces cannot.
The most common cause of brick damage is the drill bit wandering off the mortar joint and onto the brick face. This happens when the bit encounters a hard spot in the mortar and deflects sideways. The carbide tip skates across the brick surface, leaving a visible scratch that cannot be removed.
To prevent bit wandering, always start drilling with the hammer action off and at low speed. Create a clean starter hole in the center of the mortar joint before engaging the hammer action. Once the starter hole is established, the bit is guided by the hole and is less likely to deflect.
If the bit starts to wander toward the brick, stop immediately. Pull the bit out, reposition, and restart the hole. A few seconds of correction at the start is better than a scratched brick face that you will see every time you walk past the wall.
Spalling is another common damage type. Spalling is when a chunk of brick face flakes off, usually caused by water that has gotten into the brick and frozen. Drilling into the mortar joint does not cause spalling, but leaving an unsealed hole in the mortar can allow water to reach the brick, which then spalls during the next freeze-thaw cycle. Seal every hole and every bracket edge with silicone to prevent water intrusion.
If you do accidentally damage a brick face, the damage is permanent but can be minimized. Clean the damaged area and fill the chip or scratch with a colored mortar patch that matches the brick color. This is not a perfect repair, but it is far less visible than raw damage. For significant damage, the only real fix is to remove and replace the brick, which is a masonry job best left to a professional.
Avoid using adhesive mounting systems on brick. The texture of brick and the recessed mortar joints make it difficult for adhesive to make consistent contact. An adhesive mount that works on smooth stucco will fail on textured brick. Use mechanical fasteners in mortar joints for any fixture mounted on brick.
Maintenance and Removal
Solar light installations on brick should be inspected annually. The mortar joints around the anchors can deteriorate over time, particularly in older homes with lime mortar. Check for crumbling, cracking, or gaps around the mounting brackets.
Check the sealant annually and reapply as needed. Sealant typically lasts 5 to 10 years on brick, depending on sun exposure and climate. Cracked or pulled-away sealant should be removed and replaced, not just patched over. Patching over failed sealant traps moisture between the layers.
Tighten any loose mounting screws annually. Temperature cycling causes mortar to expand and contract, which can loosen anchors over time. A loose anchor is not a failure, but it should be tightened before it becomes one. If an anchor will not tighten because the hole has enlarged, remove the fixture, fill the hole with mortar patch, let it cure for 48 hours, and redrill a new hole.
If you need to remove a fixture permanently, remove the bracket and fill the holes with mortar patch compound. Use a putty knife to press the patch into the hole, smooth it flush with the surrounding mortar, and let it cure. For a better color match, mix the patch compound with a small amount of sand to match the texture of the existing mortar. The patched holes will be nearly invisible once the mortar weathers to match the surrounding joints.
When replacing an old fixture with a new one, try to use the same mounting holes if the new bracket is compatible. This avoids drilling new holes and keeps the wall as clean as possible. If the new bracket has a different hole pattern, fill the old holes with mortar patch before drilling the new ones.
The beauty of mounting solar lights on brick is that it is one of the few wall surfaces where the installation is both secure and reversible. Drilling into mortar and sealing properly gives you a mount that will last for the life of the fixture, and when the fixture is eventually removed, the wall can be restored to its original condition with a few minutes of mortar patch work. No other wall material offers this combination of strength and repairability, which is why brick remains the preferred surface for permanent solar light installation.
Take your time with each step, from locating the right mortar joint to cleaning the drill holes to applying sealant. A careful installation on brick will outlast the solar fixture itself, and when it comes time to replace the fixture with a newer model, the wall will be ready to accept the next mounting bracket with minimal additional work. That is the mark of a job done right the first time.
