Which techniques and tools should I use to build a raised vegetable garden from bricks?

Question

I have about 2/3 of a pallet of bricks left over from building our house (I didn't build it!), and I'd love to use them to build a raised vegetable garden. I have never laid bricks before, but am keen to learn! I'd like to do it properly so that it's level, subsidence doesn't crack it, and it lasts for many years.

So, what do I need to do?

A little more background:

Without measuring the bricks at this point, I'd say they are the classic size used for building houses - if necessary, I can go and measure them.

When it comes to the height of the raised bed, I'd like it to be roughly knee height; this should be about 5-6 bricks high at a guess. I'm not sure at this point what sort of shape I might like for the bed, but an oval, circle or square are definite possibilities. It would have a diameter/length of roughly 2-3 metres. I do realise that I won't be able to easily reach to the centre at that size, but I'm happy with that - I'll probably just plant herbs there as companion plants.

Edit: The climate is mostly dry, sunny and reasonably mild (generally within -5 to 30 deg C) - we get probably 10-20 frosts each winter, but the ground itself doesn't freeze, and it doesn't snow as it's too near to the coast. When it rains, it really rains lots as we're surrounded by hills so drainage is important, however the soil is fairly free draining.

We don't want to get extra bricks, so will design based on what we have. The purpose is definitely partially decorative as the bricks will match the house.

Answer 1

I'm not trying to put you off from doing it yourself, in fact I would encourage you to give it ago, but do keep in mind, laying bricks (properly) is a lot! harder than it looks.

• Keep the shape of the raised-bed simple ie Rectangle or Square.

• Take you time to install a good, strong and level foundation to build off.

• Consider placing some kind of coping stone on top of the brickwork, doing so will give you a nice looking finish, but more importantly it will greatly help extend the life of the brickwork.

To mainly make things easier for myself, I'm going to work with the "standard" UK brick size:

• 215mm x 102.5mm x 65mm (8½inch x 4inch x 2½inch)

To fully get the visual beauty of the brickwork, I would personally lay 5 courses of brickwork minimum (with the understanding 1 of those courses will be below ground level) ie

• Minimum raised-bed wall height: 5 x 75mm (10mm mortar joint) = 375mm (14¾inches) = 300mm (12inches) viewable above ground level.

• Again to keep things simple, lay the bricks in "Stretcher bond" pattern.

• Raised-bed wall thickness = 102.5mm (4inches) or what is known as "half brick" thickness.

• Using the above information means we can work on the bases of 60 bricks per m² (50 bricks per yd²).

• Therefore you have enough bricks to build: 350 / 60 = 5.8m² or 350 / 50 = 7yd²

  • Which translates into enough bricks to build: 5.8 / 0.375 = 15.4 linear metres of raised-beds @ a height of 375mm OR 17 linear yards of raised-beds @ a height of 14¾inches.

• Again to keep things simple and "standard", a raised-bed should be 1.2m (4ft) wide -- this allows you to easily work the bed without stepping into it.

  • A raised-bed can be a long as is practical.

• Therefore you have enough bricks to build a 1.2m wide x 6.5m long raised-bed @ a height of 375mm OR 4ft wide x 21½ft long raised-bed @ a height of 14¾inches.

  • Even though the brickwork is only 5 courses high, I'd be inclined to shorten the long sides down to 6m (19½ft), then with the spare bricks build a 1 brick thick (215mm/8½inch), 4 courses high (so you don't have to mess around with special coping stones and ruin the straight line of the bed), support piers halfway along the length of of those sides -- doing so will stiffen up those walls and give the raised-bed that much more strength.

• Or maybe a better option would be 2 raised-beds: 1.2m wide x 2.65m long OR 4ft wide x 8¾ft long.

  • Will prevent you from having to build "support piers" (see above).

  • If you go with 2 raised-beds, leave enough space between them so you can work easily in each bed, 600mm (2ft) minimum gap.

Hopefully I've got my above maths correct, especially where I've given/used imperial units. Please feel free to pull-up any mistakes I might have made.

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Tools you will need:

• Builders "layout" spray-paint.

• Spade to dig the strip-footing.

• Builders tarp.

• String-line.

• Bricklayers "Masonry" trowel.

• Bricklayers "Pointing" trowel (optional).

• Bricklayers pointing iron or an off-cut piece of hose works well -- either of those tools is the easiest way to point the brickwork (the mortar joints).

• Soft brush-head, used to clean-up the brickwork after pointing.

• Club hammer and Bricklayers "Masonry" bolster for splitting (cutting) bricks in two.

  • If you have one, an angle grinder works just as well -- and will make cutting mitre angles (45°) on the coping stones easy and clean.

• A 600 to 1200mm (2 to 4ft) long Bricklayers "Masonry" spirit level.

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Below advice mainly comes from helping others (skilled bricklayers) and doing it myself on the odd occasion:

• Determine the size (plan area) of the bed, based on a height of 375mm (14¾inches).

  • One "long" raised-bed: 1.2m wide x 6m long OR 4ft wide x 19½ft long, with "support piers" (see above).

  • Two raised-beds (recommended option): 1.2m wide x 2.65m long OR 4ft wide x 8¾ft long.

• Layout the plan shape of the raised-bed(s) on the ground using the builders "layout" spray-paint.

  • Then layout the same shape 100mm (4inches) offset to the outside of the above shape -- this will give you the outside face of the strip-footing.

• If constructing on a lawn, carefully take up the grass and store it properly for reuse.

• Layout the builders tarp need by, so you can easily put the excavated soil from the footing onto it.

• Dig a strip-footing, 300mm (12inches) wide x 450 to 600mm (18 to 24 inches) deep.

• Fill the excavated strip-footing with concrete.

  • Concrete should finish 75mm (3inches) below ground level.

  • Take your time and get the finished concrete as level as possible -- doing so will greatly help when you come to start laying bricks.

• Let the concrete set-up (cure) for at least 24 hours before starting to lay bricks.

• Either use ready-mix bags of brickwork mortar or mix your own.

  • If mixing your own, measure out the materials by volume (use a bucket), doing so will ensure you achieve a consistent "finished" mortar colour.

  • Mix strength by volume of materials, 4:1 or 5:1 ie

  • 4 or 5 parts soft building sand.

  • 1 part Portland cement.

  • Thoroughly "dry" mix together the two materials.

  • Add a suitable Mortar Plasticiser to a bucket of clean water -- this will make the mortar more workable, easier to use.

  • Add the water (with plasticiser) slowly to the dry mixture, mixing together as you go -- you want to end up with a thick (but workable), lump free mixture (see below image, click to enlarge).

Image source: Wikipedia

• First, build the corners of the raised-bed(s), take your time...

  • Make sure the first course of brickwork is level.

  • Make sure the corners are square (90°) and plumb (upright, not leaning inward or outward).

  • If you cut corners on the above couple of points, you will be "fighting" to correct the brickwork as you progress further.

• Once you've built the corners (up to their final height), use the bricklayers pointing iron or off-cut piece of hose to point the brickwork (the mortar joints).

  • Then take the soft brush-head and clean (wipe-off) the brickwork.

• With the corners built, take the string-line, line it up with the top outside edge of the first course of brickwork, and run it between one corner and another corner.

  • If building one "long" raised-bed and working on one of the long sides, you will want to build the "support pier" (see above) before moving onto the next point.

• Then complete this course of brickwork using the string-line as a guide for the bricks.

• Move the string-line up one course of bricks, then complete that course of brickwork... Repeat until you've finished that one face of the raised-bed.

• Once you've built that face of the raised-bed (up to its final height), take the bricklayers pointing iron or off-cut piece of hose and point the brickwork (the mortar joints).

  • Then take the soft brush-head and clean (wipe-off) the brickwork.

• Repeat the above steps to fill-in the other three faces of the raised-bed.

• On the second course of brickwork (first course viewable above ground level), remove (omit) the vertical mortar joint between the bricks, do so near the corners, then every 3rd joint along the length of the walls -- this will provide some drainage from the raised-bed.

• Optional, but highly recommended -- to help prolong the life of the brickwork, lay a coping stone around the perimeter.

• Before filling the raised-beds with suitable material, get some outdoor screen mesh fabric (small off-cuts) and place those on the inside face of the brickwork over the vertical joints you omitted -- this will help those drainage "holes" stay clear of debris and functional.

• If the soil you excavated for the strip-footing is ok! (dark, crumbly, etc) I would take that and mix it with high quality "organic" material (compost, leaf mold, etc).

• On the other hand, if the excavated material isn't ok! (clay, clumpy, etc) I wouldn't use it in the bed, instead I would bring in a 50/50 mixture of finely sieved top soil and high quality "organic" material (compost, leaf mold, etc).

• Add the material in 6inch (150mm) layers, "lightly" tamping down each layer as you go.

• Make good around the perimeter of the raised-bed at ground level -- if you built on a lawn, take some of the grass you stored (properly) for reuse and lay that back down.

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Good luck! and I hope the above makes some kind of sense. Any questions, please ask...

Answer 2

As a novice bricklayer, I'd recommend sticking with a rectangle. I think a circular shape will be more challenging.

The following is based on my limited experience with laying larger cement blocks.

1. Plan first!

   1. Determine the location of your bed.
   2. Determine the dimensions you want. You mentioned "knee height" -- maybe 40-50cm?
   3. Figure out how many courses of bricks (height), and the length and width and number of bricks in each of those dimensions. Don't forget to account for the mortar joint between the bricks.
   4. Verify that you have enough bricks to finish the job. If you don't, then either make the bed smaller or get more bricks.

2. Get your tools.

   • Wheelbarrow for mixing mortar.
   • Short-handled hoe for mixing mortar.
   • Trowel
   • Scrap board -- about a 30x30cm piece of plywood to use as a sort of palette. (Optional.)
   • Long level (4').
   • Stakes
   • String
   • Rubber mallet
   • Stone chisel for splitting bricks
   • Jointer for smoothing the mortar in the joints
   • Gloves

3. Prepare the area for the bed.

   • Remove weeds/sod/turf in the area to receive the bed.
   • Level the area. Use your long level to ensure that the area is perfectly level. If you start on uneven ground it will be very challenging to get the courses of bricks to come out evenly.
   • Drive stakes beyond the four corners, and connect them with strings. The strings should cross at the corners -- you don't want the stakes in the way of your bricks. Use 3-4-5 to ensure that your corners are square. Then double check for square by measuring diagonally from corner to corner -- both diagonals should be precisely equal.

4. Prepare a foundation for the bricks. In the area where the bricks are to be laid, excavate the soil to a depth of 12". Backfill with road sub-base material (crushed rock) and compact it thoroughly as you fill. Use the long level to verify that the base layer is perfectly level. Do not completely fill -- leave 2" below grade. The foundation should be centered along the string lines so that the outside of the bricks will be in line with the string.

5. Mix the mortar. Follow directions on the bag. Mix it in the wheelbarrow with the hoe. Add small amounts of water at a time! It is very easy to overdo it with water. It's easy to add a little more if the mortar is too dry, it's impossible to take water away. You want it about the consistency of peanut butter. Don't mix too much at a time -- it will be wasted if it sets up before you can use it. (And it's hard to clean up!) A cool, overcast day is ideal -- you don't have to worry about the mortar setting as quickly.

6. Lay your first course of bricks. Since you left 2" below grade, the first course will be embedded by that much. Start at a corner. Set the bricks into the center of the foundation you created, making sure that the outside edge of each brick is in line with the string. Tap then into the base with the mallet. Before you set each brick, use the trowel to put a bit of mortar on the end of the brick to "glue" it to the previous brick. (There's a knack to this that I think you can only get with experience.) You can use the mallet to tap the bricks together (but I'm not sure this will be needed with bricks; my experience is with larger concrete blocks). Keep the gaps even. Use your level to check that your bricks are level along both axes (i.e. each brick is an even height and the wall itself isn't tipping inward or outward). At the corners, use a large carpenter's square to make sure you are making a perfect 90° angle.

7. Lay the subsequent courses. Start at a corner. Offset the bricks from the previous course, so that the joints don't overlap. This is essentially the same as the previous step with the addition of a layer of mortar on the bottom of each brick. If you didn't get the previous course perfectly level, you'll pay for it now! Use the level frequently to make sure everything is plumb and even. Keep the offsets consistent -- both height and width. (If your heights are inconsistent, the course will not be level. If your widths are inconsistent, your course will be too short or too long and the corners will be messed up.) Adjust your string height as you go so that the string is the height of the bricks -- it makes a better guide this way.

8. (As you go along.) When the mortar has set up a bit -- just enough so that a fingerprint shows -- use the jointer to smooth out the joints and remove excess.

9. Clean up promptly! Wash out the wheelbarrow, clean off the hoe and jointer with a garden hose. Mortar is pretty easy to clean up when it's still wet. Once it dries, it's nearly impossible.

10. Backfill. Add 2" of coarse sand in the foundation trench to bring it up to grade.

11. Fill the bed with appropriate growing media, plant, and enjoy.

I don't have tons of experience, so if anyone who knows better wants to correct me on some point or add something I've missed, please do so.

Answer 3

I can't speak about masonry, but I'm going to suggest an alternate shape that might be a good use for your bricks. You can lay them in an irregular spiral to form a Spiral Herb Garden which you fill with dirt. Normally you see these done with fieldstone, but I think bricks would work. The center is the highest point and you construct a ramp that spirals outward until it comes flush with the ground. Think of a sandcastle.

The advantage of the spiral are that you can devise zones of different soil and drainage qualities to suit different plants. The center will more rapidly drain and can be filled with different soil (more sand for instance.) The outer spiral can be populated with plants that need more water.

You don't have to mortar them, depending on how you arrange the bricks, so less skill is required.

I've observed my wooden raised box and noted the rosemary and rhubarb are fairly drowning; these would be candidates for moving to higher ground in a spiral bed.

You can find many beautiful examples by googling for Spiral Herb Garden