How to Build a Greenhouse Base Using Paving Slabs [7 Steps to a Sturdy Greenhouse]

To build a greenhouse base out of pavers, you will need to:

• Choose a site for your greenhouse and mark it off.
• Excavate the Greenhouse site to a depth of 7 inches (18 cm) and level the area.
• Add 4 inches of paver base to the excavated area.
• Pour 1 inch of paver sand on top of the paver base.
• Lay pavers in the desired pattern.
• Use a wet saw or angle grinder to cut pavers as necessary.
• Fill joints between the pavers with polymeric sand.
• Erect your greenhouse on the paver base and secure it with concrete anchors.

By following these steps, you will create a solid, waterproof greenhouse floor that resists invasion from insects and rodents. However, you can also alter these steps slightly to create a natural-floor greenhouse with a paver edge, or a paver floor that drains into the ground below. We’ll cover all these methods as we go.

7 Steps to Build a Greenhouse Floor From Pavers

Pavers make an excellent greenhouse floor because they are so versatile. With pavers, you can create a solid floor as strong as a concrete base, or a paver floor that allows water to drain through it into the soil. What you’ll need for this project is:

Tools and Materials:

• Stakes
• String
• Measuring tape
• Shovel
• Carpenter’s level
• Tamper or roller
• Masonry saw or angle grinder
• Electric drill
• Paver base
• Paver sand
• Pavers
• Concrete anchors
• Mortar (optional)
• Polymeric sand (optional)

Armed with this equipment, work gloves, and a weekend, you can install a solid base for your greenhouse that will be both sturdy and attractive.

Choose your Greenhouse Location

Choose a location on the south or southeast side of your property for your greenhouse. This will maximize the amount of sun your greenhouse receives, especially during those short winter days. Choose an area that doesn’t receive shade from trees or fences. Once you have determined the right spot, mark out the perimeter of the greenhouse base with stakes and string.

• Place your greenhouse where it receives full daytime sun (typically the south side of your home).
• Do not place your greenhouse in a shaded area.
• Mark the greenhouse site using the measuring tape, stakes, and string.
• When driving the stakes, keep in mind you will be excavating the area.

It’s important to note that the area you mark off for your greenhouse will be excavated in the next step. You may want to drive your stakes into the ground just outside the greenhouse dimensions, so you can dig without uprooting the stakes that will act as your guides.

Dig the Foundation

Use your shovel to excavate the site where your greenhouse will stand. Dig down to a depth of at least 7 (18 cm) inches. You will be pouring 4 inches (10 cm) of base and 1 inch (2.5 cm) of sand. If you are laying 2-inch thick (5cm) pavers, 7 inches of excavation will make your greenhouse level with the surrounding soil. If you are using 4-inch thick (10 cm) blocks instead, excavate to a depth of 9 inches.

• Excavate the marked site of your greenhouse to a depth of 7 inches (18 cm).
• Use the carpenter’s level to make sure the excavated area is level.
• Where possible, dig more to achieve a level base rather than adding soil.

Use a long carpenter’s level to check the level of the ground once you reach the desired depth. When achieving a level foundation, it’s always better to dig more than it is to add soil. Undisturbed soil is harder and resistant to settling. If you add soil back in, it is likely to compress, making for an uneven foundation.

Add Paver Base

Now that your site is excavated and level, pour 4 inches (10 cm) of paver base. This gravel material improves drainage and will keep your pavers in place.

• Add 4 inches (10 cm) of this paver base to your excavated site.
• Use a tamper or roller to compact the base.
• Check the level and depth of the paver base. Add or remove the base as necessary.

Tamp or roll the base to compress it into place. Check the ground level of the base as you go. A flat foundation is a key to success.

Pour Paver Sand

Pour 1 inch (2.5 cm) of paver sand over the paver base. This makes the perfect bed to lay pavers for a solid foundation. Like the paver base, the sand should be tamped into place and leveled.

• Pour 1 inch (2.5 cm) of this paver sand over the paver base material.
• Tamp and level the paver sand.
• To prevent greenhouse flooding, add an extra 1/4–1/2 inch (1 cm) of paver sand.

If you would like your greenhouse foundation to stand a little higher than the surrounding lawn, add an extra 1/4–1/2 inch of paver sand. This will cause the pavers to stand up above the lawn, which prevents excess water from flooding into your greenhouse from the yard.

Lay Pavers and Cut Them to Fit

Lay your pavers atop the sand in the desired pattern. You can follow regular lines or use a bricklayer’s pattern. Where pavers do not fit the prepared site, measure and mark them with a straight line. Use a masonry saw, wet saw, or angle grinder equipped with a masonry blade to cut the pavers to the desired size.

• Lay your pavers on top of the leveled sand.
• Cut pavers to fit with a tool equipped with a masonry blade.
• If desired, add mortar to the corners of the pavers, to adhere them to one another.

If you want to make your pavers more securely fastened to one another, place a small amount of mortar at the corners of each paver as you lay it. This will “glue” the paver to its neighbors while still allowing gaps for water to drain through to the soil below.

Fill Seams with Mortar or Polymeric Sand [Optional]

A paver floor with gaps between the pavers is extremely functional and in many cases, desirable. Any water that reaches the floor during plant watering will drain down through the pavers. This eliminates flooding issues. However, if you want a finished paver look or want to prevent infiltration from pests or weeds, you can fill the gaps between the pavers with mortar or polymeric sand.

• A paver floor with unfilled seams between the pavers drains well. You may want to leave your paver floor as-is.
• If you want to fill seams, use mortar or simply pour dry polymeric sand into the seams.
• Sweep pavers after pouring polymeric sand so the sand is only present between the pavers.
• Water polymeric sand with a gentle shower setting from a hose-end nozzle. The sand will harden to concrete consistency when it dries.

If you are using polymeric sand to fill the joints between pavers, use a gentle setting on your hose-end sprayer to soak the sand without blasting it out of the seams between the pavers. Polymeric sand hardens like concrete as it dries. If water forces it out of paver seams, it will harden on top of your pavers.

Secure Your Greenhouse to the Pavers

Now that your foundation is complete, erect your greenhouse on top of your pavers. It’s essential to anchor your greenhouse to the paver floor to keep it from being shifted by wind and weather. Your greenhouse should have anchor holes in the lower edge of the bottom supports. Drill pilot holes through the anchor holes and into the pavers below. Then, drive in concrete anchors.

• Construct or move your greenhouse on top of the paver foundation.
• If possible, construct only the greenhouse frame. Install glass panes after anchoring the greenhouse.
• Find the anchor holes in the lower frame of the greenhouse.
• Drill pilot holes through the anchor holes, into the pavers below.
• Secure the greenhouse to the pavers using these concrete anchors.
• Use an appropriately-sized masonry bit to drill pilot holes.

When drilling pilot holes, use a specialized masonry bit to prevent damaging or cracking pavers. Avoid damaging your greenhouse during this process. Remember, the pilot holes and anchors should go through the corresponding anchor holes in your greenhouse. There should be no need to modify or drill new holes in your greenhouse.

How to Use Pavers to Build a Greenhouse Base with a Soil Floor

If you would like to keep your greenhouse in place on a paver base without completely covering the ground with pavers, you can instead create a perimeter of pavers. The process is similar to the one above, except with less excavation and fewer pavers.

• To create a greenhouse with a paver base but a soil floor, simply excavate only the outer perimeter of the greenhouse site.
• Follow all the steps for laying paver base, sand, etc. for your ring of pavers.
• Construct your greenhouse atop the ring of pavers and anchor it in place.
• This allows for a solid greenhouse foundation, but you can plant directly in the dirt inside your greenhouse.

Now you can use the interior of your greenhouse as a mini, covered garden. You can plant whatever you like directly in the soil. However, it is advisable to plant at least 8 inches (20 cm) from the paver base, to avoid disturbing the foundation.

How Do You Build a Greenhouse Base With Paving Slabs?

To build a greenhouse base from pavers, first, choose a site for your greenhouse. Then, excavate the greenhouse site to a depth of 7 inches, ensuring the soil floor is level. Pour 4 inches of paver base into the excavated area and tamp it into place. Follow this, pour 1 inch of coarse sand over the base material and tamp this into place. Then, place your pavers, cutting them to fit as necessary. For extra stability, you can fill the joints between the pavers with mortar or polymeric sand as desired. Finally, build your greenhouse on top of the paver foundation and use anchor bolts to secure the greenhouse frame to the pavers below. This will provide a sturdy base for your greenhouse.