Cutting Allan Blocks and their caps is always required. At a minimum you will need to cut blocks and caps to length, and frequently you need to customize blocks or caps to make them fit tightly, especially when building staircases.
To cut blocks we use a gas-powered Stihl TS420 saw with a 14” concrete blade. This is a hand held saw that is highly portable, and quick.
To avoid breathing the silica dust that this saw produces when cutting concrete, wear a tight fitting N95 dust mask, and or cut with water if temperatures allow.
If it is freezing, they do make a 2-shop vac setup that can capture the dust before its airborne.
For the caps, free hand cutting isn’t ideal as its impossible to make a perfectly square and plumb cut. If you’re just cutting one end to shorten a cap freehand is acceptable, but if you’re doing 45-degree mitres, or cuts that will be visible you should use a table saw.
Wet brick saws are popular as they have been around for a long time, and are kind of affordable. The newest saw is a 16” dry cutting saw that eliminates 99.5% of silica dust, and Is OSHA / WorkSafeBC compliant.
Pro tips on cutting
Factory edges have a 45-degree bevel to them. When you cut a block, you will lose this factory edge. Choose which angle you will most view the retaining wall from, and make your cut on the far side of the block. This will keep your eye from seeing the cut end most of the time.
Plan your retaining wall so that you don’t need to make cuts close to corners, stairs, or other focal points.
This will keep your “center” clean. Adding a block or two and then having the cut moves it a little further away from the area you want it to look its best.
Do your best to avoid small blocks or cuts. It’s a lot more work, but instead of a 4” block, cut 3” off of the blocks on either side. This will turn your 4” block into a 10” block and it will blend in much better.
What we do is cut the blocks on either side down so it maintains a 4” overlap on the seam, and then cut the middle block.
Blocks should overlap at a minimum ¼, which is about 4.5”. To accomplish this the 2nd row usually offsets the first row by half a block.
Typically, a full block is just cut in half, as its quick, and onsite. If the budget and time allow you may want to consider using a factory half block. This preserves all of the clean ends. It looks a little better, but is more inventory, and work to coordinate when ordering.
Half high blocks are great for adding 4” to the wall height vs the normal 8” every row. They also are great for doing step down as they draw out the step downs.
It looks more natural, and it softens the normal 8” step down.
Corners are available in regular 12” long, or professional 18” long. They are the standard 8” high, and are faced on 2 sides. These are used for “outside” corners.
12” Allan Block corners are best used for placing sideways to finish a wall off, or when building step up/downs. Corner step down drop the wall 8” every 12” and is a taller step down compared to the half high’s.
The pro 18” corners are what you would want when building outside corners for staircases.
You don’t have to use the bigger ones, but they do tie the two walls together stronger, and provide 36” of “stitching” the two walls together vs. the smaller only provides 24” of “stitching”.
Pro corners provide a 33% stronger outside corner.