© 2008 by Raymond Alexander Kukkee
Why Build a Patio With Slate?
Slate is natural stone, an elegant, versatile building material that may be used anywhere; on a floor, on walls, outside, or as life-time durable, beautiful roofing. Installed on a patio out in the sunlight, it becomes even more attractive. Have you wished for an attractive, upper-scale patio to party on for those warm, great summer weekends?
A slate patio may be the perfect solution for you. Here’s how to build a patio with slate.
Slate comes in a number of colours, pre-cut sizes and thickness. A natural metamorphic rock that splits into layers cleanly, depending upon the source, slate can be highly variable in colour from deep plum to shades of green and blue-gray. This beautiful, durable rock can provide an excellent patio surface. With some planning, attention to detail, elbow grease and dedication, you can actually build a long-lasting slate patio in a weekend. First we must do some careful planning.
Design and Other Considerations.
Any worthy patio project deserves planning in detail. How large do you wish to make your patio? Do you typically have only two guests when entertaining, or groups of twenty? If the project required is too large, consider doing it in stages.
Define the placement of your patio carefully. Can you step outside at ground level through a sliding patio door off the dining room? Most entertaining is done in the evening or afternoon around meals, so thought must be given to access to the house and the availability of shade and sunlight.
What shape will it be? Square and rectangular structures are simpler, but circular, hexagonal, and other shapes can be created with care. Rock cutting may be required.
Will the patio be installed next to the house foundation? Choose the option to install a short , wide walkway between the doorway and the patio to take advantage of the creative and attractive landscaping possibilities between the structures.
Consider historic traffic patterns in the yard. Allow for walkways that will not allow traffic to interfere with the pattern of use you predict for your new patio. Simultaneously, be creative and allow for future additions and walkways,– perhaps attached to eliminate other problems, for example, the typical and unsightly worn path to the garden shed.
DO remember to obtain a building permit if required from your municipality or other jurisdiction.
Consider drainage patterns of your location. If you have water collecting on your location, it can be problematic. Consider installing a French drain or use other methods to handle excess water or divert it from the location.
For our project we have chosen to build a rectangular patio 8′ wide x12 long bedded in sand, but you can build a patio any size or shape using the same procedure . We will need the following tools, materials and supplies:
- Pickets and stakes
- Carpenter’s line
- Carpenter’s level 4′
- Saw and hammer
- Shovel (Preferably a sharp, flat spade)
- A broom with stiff bristles
- Garden rake
- A saw with a stone-cutting or masonry blade (if required for more complex design)
- A screed. (A simple tool for leveling sand. Build it as required using dimensioned lumber.)
- Garden hose and water
- A powered vibrating plate packer if available, or a manual plate tamper.
- Sand (use clean construction sand, no trash, roots or dirt allowed)
- Ground fabric (dense ), or black plastic appropriately sized. Note that ground fabric allows water to drain away, so is preferable.
- Slate Choose your slate sizes carefully considering the style of framing you are planning to use. Doing so will minimize the cutting of stone. Remember, 1″ thick is the minimum thickness for slate bedded in sand. Thin slate 5/8″ or less must be bedded on a concrete slab in thin set mortar to avoid cracking and failure. If you wish to build a concrete slab for your patio, see “How to Pour a Concrete Slab“.)
- Framing materials: Note: Framing materials may be treated dimensioned lumber (2×4), treated landscaping timbers, masonry, or the patio can be built “frameless”. For masonry framing, a 4″x8″ deep steel reinforced concrete footing is required in severe-frost areas .( For simplicity and ease, on our project we will use pressure-treated 2×4″ wood framing.)
- Fasteners: for framing, use galvanized, anodized or stainless steel fasteners to construct the framing. Use screws rather than nails, which may eventually loosen.
Let’s Build the Patio!
1. Delineate the chosen area and shape with pickets and a line to help visualize the project. It’s easier to change the shape of your patio now than later! Orient the patio to your liking, and do verify clearances required from adjacent lot lines if applicable. If it is satisfactory, verify the dimensions again, and start digging.
2. Remove the sod or grass. Use it elsewhere to fill in holes, repair poor sections of lawn, give it to someone that needs it, or barter it for some help you can use about now! *NOTE: If you are building a “frameless” patio, DO cut the edges carefully and cleanly to a line with a flat, sharp spade. The remaining sod will act as a natural frame.
3. Excavate to 3-1/2 ” deep, ensuring the excavation is level and cleanly cut. Note that depending on soil conditions, you may wish to excavate an additional 6″ deep and install a 6″ layer of gravel suitable for packing.
4. Construct the frame. *Remember the slate stones will have spaces between them, so “lay some out” to check and verify the exact inside dimensions required for the frame. Allow 1/4″ to 3/8″ spacing.
5. Paint or stain the frame as required if desired at this stage.
6. Install the frame in the excavation. To square it, measure 3′ from one corner (inside) and 4′ (again, inside) the other way from the same cornerinstalling pencil marks on the frame. When the two marks are 5′ apart, the corner is perfectly square.
Drive stakes in on the outside of the frame to BELOW the surface of the frame and attach the frame securely to the stakes with screws. Check to ensure the frame is as close to level as possible.
7. Carefully adjust the level, removing or adding more sand or *gravel as needed. This is to allow for adequately thick sand bedding. (*Remember to install the compacted gravel layer first, leveling and compacting it with a mechanical packer if appropriate)
8. Install a sheet of ground fabric on top of the gravel to prevent the emergence of weeds. Heavy black plastic will serve the same function, but ground fabric is preferable since it allows water to drain through it.
9. Place 3″ of sand in the excavation and level it using the screed. *Construct a screed using a 2×4 that is a foot longer than the frame. If your slate is 1″ thick, notch both ends of the 2×4 out 1″ which will allow the “belly” of the 2×4 to extend down into the frame to a depth of one inch. Alternatively, fasten a second 2×4 the length of the INSIDE measurement of the frame to the first 2×4. Construct it to allow it to extend down into the frame for the thickness of the slate chosen.
To use the screed, place both ends on the frame and with a helper, drag it across the surface, leveling the sand to perfection. Add or remove extra sand as necessary.
10. Wet the sand down with a fine spray of water and pack it thoroughly. Use a vibrating plate packer if available, or a plate tamper. The more firmly the sand is packed, the less likely severe settling of the slate will occur later.
11. Add more sand, screed again, tamp and fill the sand layer as required until the surface is perfect.
12. Lay out the slate using spacers. Commercial spacers are available, or use temporary spacers you can make yourself, ensuring the spacing is even.
13. Bed each stone securely as you go. Because slate is split naturally, all slate pieces may not be uniformly thick, so add or remove sand as required to keep the top surface of the slate as even as possible. Bed each slate tile into the sand individually with a rubber mallet, or alternatively, place a short piece of 2×4 across several stones simultaneously and tap judiciously to level them. Remember, slate can break !
14. Add sand to the surface and brush it into the cracks using a broom. Pack the sand down into the spaces, but avoid disturbing the tiles. Leave the surface of the sand below the tile surface temporarily.
15. Apply clear slate sealant to the slate surface if desired. *Note: Some slate will develop stains from splashes of grease, liquids or spilled foods, so if your intended use of the new patio is barbecuing, do consider applying a slate sealant.
16. Allow the sealant to dry and apply a second coat if required.
17. When completely dry, apply and compact more sand into the spaces, wetting it down to provide maximum compacting.
Now all you need to do is sweep away any excess sand, put away the tools, and haul out the barbecue. Congratulations, you have a brand-new slate patio, and the best part is, you can extend it any time you wish, because you already know how to build a patio with slate!
Is that Incoming I hear?