Pavements made of separate pieces are usually easy to fix or swap out, and the repairs look natural. But pavements made from one big piece, like tarmacadam or concrete, need cutting and patching when they break, which can leave noticeable marks.
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Replacing individual elements
This approach is applicable to brick and block paving, as well as flags/slabs, and any other paving variety comprised of individual units.
Replacing block paving involves removing the existing blocks and installing new ones.
To replace an individual unit or a section of paving, the targeted unit must be fully extracted from the pavement. If other units need to be removed, they can be easily taken out afterward. There are two straightforward methods for removing this initial unit.
The non-invasive approach
In the non-destructive method, we lift the unit carefully using a trowel or a bolster’s heel, gently prying apart two opposite edges of the block or flag. This technique is shown in the picture for removing a block, but it works the same for flags. With the levers in place, we gradually lift the unit by wiggling it up, adjusting each side a little until it comes off the pavement. Usually, this method doesn’t damage the block, so we can use it again.
- Utilize the point or heel of the trowel to lift one edge of the block. In this instance, a half-block is initially removed, as the cut edge facilitates easier insertion of the trowel point/heel.
- The initial trowel is employed to keep the first (cut) edge raised, while the second trowel is utilized to lift the opposite edge.
- Continue to gently jiggle the trowels to coax the sides upwards alternately until the block becomes free.
The destructive method
A sharp chisel can be employed to penetrate the block, subsequently leveraging the broken parts free from the pavement. The chisel, or a pointed chisel, is driven into the block at approximately a 30° angle from vertical until the block fractures. It’s important to note that this method renders the block unusable, hence, ensure you have spare or replacement blocks available to replace the broken one.
After the initial unit is taken out, adjacent units can be fairly easily removed by leveraging from beneath. With flags, it might be required to cut out any mortar joints to release the flag, and blocks may sometimes be firmly held by jointing sand, necessitating a gentle jiggling to free them. It’s worth noting that some blocks and bricks, especially clay pavers, have two usable surfaces. By flipping them upside down, a new, undamaged, or unmarked face should be revealed.
Remove the necessary portion of the pavement, stacking the blocks nearby for reuse. Clear off any jointing sand clinging to the block edges or remove any mortar stuck to the flag edges. Prepare the exposed bedding layer by floating, troweling, or screeding it to accommodate the replacement of paving units. If adjustments to levels are needed, add or remove bedding material accordingly. For larger areas, verify the surface level of the bedding layer using a straight-edge timber and one of the salvaged blocks as a reference. Leave the bedding layer approximately 5mm higher to account for re-compaction.
After preparing the bedding, replace the blocks/flags as needed, using spare or replacement units as necessary, and seal with dry jointing sand or mortar joints. Ensure the repaired area is re-consolidated, preferably with a vibrating plate compactor for block or small-element paving, or a mall for other flags. Reevaluate the level of sealing sand after 3-4 weeks and add more if needed.
When we swap out damaged or stained block paving with new ones, it can stand out because the new ones might look brighter and fresher. To avoid this, we give each client extra blocks that match the originals. This helps make sure the replacements are from the same batch as the originals, since manufacturers can change how they make blocks over time..
In cases where batch-matched paving isn’t available, the visual impact of new blocks can be mitigated by blending them with clean existing blocks sourced from the immediate vicinity of the staining. For instance, for a 1m² stain, we might lift 2m² of paving, discard the spoiled blocks, mix in the replacement blocks, and relay the entire area.
In the majority of cases, after 12 months, it’s nearly impossible to distinguish between the original paving and the replacements.
Replacing flags/slabs
For other types of pavings that are mortared in, the method for replacement is quite similar to what was described earlier for block paving. The mortar joint needs to be removed, preferably using a power saw, although it can also be chiseled out with a hammer and bolster. Once the paving unit is levered out of the pavement, it should be stored or discarded as needed, and the bedding layer prepared for reseating the unit. Apply mortar to the receiving edges of the pavement before replacing the units. Tap them down to level using a paviors mall, and then proceed to repoint the joints.
Patching non-elemental surfaces
Tarmacadam, concrete, pattern imprinted concrete (PIC), and resin surfacing are considered ‘monolithic’ rather than modular, which means they can only be repaired in patches. However, these patch repairs typically remain noticeable regardless of efforts to conceal them. PIC and resin surfaces are especially challenging to repair without the patch being glaringly obvious. Even bitmac, commonly perceived as ‘black,’ is often difficult to match in terms of color, texture, wear, and weathering.
In most cases, it’s advisable to enlist the original contractor for repairing or patching these surfaces whenever possible. They are likely familiar with the materials and techniques used initially, giving them the best chance of effecting a repair that is less noticeable.
Patching Tarmacadam
Mark out the area to be patched, ensuring there is ample working space and keeping clear of any cracks or crumbling by at least 100mm. Utilize a dust-suppressed Power Saw to cut through the surface along the entire perimeter of the repair area. The unwanted surfacing can then be chiseled out, jack-hammered, or removed with a pick and spade, and disposed of off-site. The saw cuts ensure a clean, straight edge for the patching process. While a normal handheld cut-off saw is typically sufficient, a trolley-mounted floor saw is preferable for larger areas.
Before adding new material, cover the vertical edges of the cuts with a jointing compound called “cold pour,” which you can get from civils’ merchants. This compound seals the joint to stop water from getting under the surface, which could cause the repair to fail when it freezes and thaws.
For the repair, it’s advisable to utilize fresh, hot bitmac, applying it in at least two layers and compacting each layer using an asphalt punnel, vibrating plate compactor, or roller. Seal the ‘seams’ of the repair with cold pour compound (as mentioned earlier) to prevent water infiltration. Although this may increase the visibility of the repair, it significantly decreases the likelihood of failure due to water penetration into the joint.
Macadam suppliers generally prefer deliveries of 3 tonnes or more, and they may apply steep part-load charges for smaller orders. However, certain batch plants may accommodate smaller loads, such as half a tonne, on a trailer or private wagon. When transporting macadam, it’s crucial to cover the material with a tarpaulin or similar to retain as much heat as possible. Otherwise, it can become challenging to work with.
FAQ
Using pre-packaged macadam
Most builders’ merchants offer pre-packaged repair macadam, which can be significantly more cost-effective than ordering hot bitmac in small amounts. Priced at approximately £8 for 25kg, this translates to £320 per tonne, compared to £50-60 per tonne ex-works. However, for loads less than 1 tonne, batch plants often apply a part-load charge of around £150-180. Therefore, quantities greater than 1 tonne are best purchased as hot, fresh material.
For reference, a 25kg bag of repair bitmac typically covers around 0.45m² at a thickness of 25mm. However, it’s important to maintain a minimum depth of 70mm for any macadam surface. At this thickness, the coverage is reduced to approximately 0.16m² per 25kg bag, meaning it would require just over six bags to cover each square meter.
The pre-packaged tarmacadam has been treated with a cutting agent or “doped” to delay setting until exposed to the air, allowing the doping oils to gradually evaporate over time. While the packs are supplied cold, they work best if left in a warm area for several hours before use. Once removed from the packaging, the tarmacadam is spread out as needed and compacted to level, following the same procedure as with hot tarmac. It may take several weeks for the doping oils to completely evaporate, but the compacted surface should be usable almost immediately.
If the surface of the repaired tarmacadam remains tacky and sticks to car tires or shoe soles, sprinkle a fine sand over the surface, similar to flouring a work surface before rolling out pastry. The sand will gradually wash away over time.
We find these pre-packaged repair tarmacadams somewhat underwhelming. While they serve their purpose for very minor repairs, we wouldn’t recommend them for areas larger than a couple of square meters. They stay soft for several weeks and are susceptible to penetration by any point load, such as a motorbike’s side stand or a lady’s stiletto heel.
For patching areas ranging from 2 to 20 m², you might be able to locate a local tarmacadam contractor willing to order an additional tonne or so if you incentivize them with beer vouchers.
Bitmac cover-ups
There are several products on the market that enable you to rejuvenate an existing tarmacadam surface to give it a fresh appearance. Some products function essentially as paints, while higher-quality options actively adhere to the existing tarmacadam and revitalize the bitumen binder. These products are most effective when used to cover an entire driveway or courtyard rather than just touching up patches.
Known by various names such as Tarmac Sealers, Tarmac Sealcoats, or Tarmac Paints, there is a growing variety of options available. However, it’s crucial to select the most suitable product for each specific job.
They can effectively conceal minor imperfections or patches on tarmacadam surfaces, or simply refresh the appearance of a worn-out driveway. These products are occasionally stocked by builders’ merchants, larger DIY stores, and construction chemical suppliers in standard black or a burgundy red shade. However, if smaller quantities are needed, they may need to be specially ordered.
The macadam surface slated for treatment must be thoroughly cleaned and devoid of dust and debris. We typically power-wash the surface and let it dry before applying the sealcoat product. Generally, two coats are necessary, and it’s advisable to use a long-handled squeegee for application (which saves strain on the back!). Allow each coat to dry before applying the next one. Typically, they dry within 2-3 hours and can withstand traffic once completely dry.
Patching concrete
Similar to macadam (bitmac/tarmac), repairing concrete often results in visible work. Due to various factors, achieving an exact match with the existing surface is typically impractical or impossible. Even if an exact match were attainable, noticeable lines would remain where the old surface was cut out and the new surface installed.
This reality holds true whether it’s a basic, unembellished concrete surface or a highly adorned, colored, and textured pattern imprinted surface. Achieving an invisible repair is simply not feasible.
Stains alone typically aren’t enough reason to justify breaking out and patching a concrete bay. However, certain circumstances necessitate renewing the concrete, such as salt or frost damage, repairs to underground services, or the removal of damaging tree roots. This section will address two types of repairs: shallow surface repairs and full-depth repairs.
Shallow repairs
This method is appropriate for fixing minor surface imperfections or flaws, like salt and frost damage. First, mark out the area to be repaired and cut the perimeter with a power saw to a depth of at least 40mm. Then, remove the damaged concrete surface by chipping it out with a hammer and chisel or a demolition hammer from a hire shop. If replacing salt or frost-damaged concrete, ensure that all loose and unsuitable material is removed to a depth of at least 40mm. Clean the repair area thoroughly and brush away as much dust as possible.
Next, prime the exposed concrete surface with PVA or SBR bonding agents, or etch it clean with an acid-etching fluid. The fresh concrete to be used for the repair should be a high-strength mix, with PVA, SBR, or a hardening agent added. Typically, a granolithic concrete is preferred for such repairs. For further discussion on high-strength and granolithic concretes, refer to the Mortars & Concretes Page.
Spread the fresh concrete evenly, tamp it to level, and finish it with floating as needed. Ensure that the fresh concrete is firmly worked into the edges of the repair and aligns flush with the existing surface.
It’s advisable to cover or fence off wet concrete since neighbourhood cats and curious children tend to leave their pawprints behind. The repair can typically withstand traffic after 3-4 days.
