Foundation Frame for Riga IIIs
Foundation Frame for Riga IIIs Greenhouse
The Riga IIIs Foundation Frame is the purpose-built ground installation solution for the Riga IIIs greenhouse — the smaller "S" variant of the Riga III series. Buried in a trench and backfilled with soil, it securely anchors the greenhouse directly to the ground without requiring a concrete foundation, while also raising the greenhouse height for additional headroom and growing space.
*Free shipping only when purchased together with a Riga greenhouse. Ordered separately, an additional shipping charge applies.
Key Features
- Designed specifically for the Riga IIIs greenhouse model
- Buried in-ground installation — no concrete required
- Backfilled with soil to securely anchor the greenhouse
- Raises the greenhouse height — adds headroom and growing space
- Purpose-built Riga accessory — engineered to fit the Riga IIIs footprint exactly
Specifications
| Compatible Model | Riga IIIs |
| Installation Method | Buried in trench, backfilled with soil |
| Foundation Required | No concrete — installs directly into ground |
| Benefit | Secures greenhouse to ground; adds height for headroom and growing space |
| SKU | RIGA-IIIS-BASE |
| Price | $1,049 |
| Shipping | Free when purchased with a Riga greenhouse; additional charge when ordered separately |
How the Foundation Frame Works
- Dig a trench around the perimeter of your greenhouse site to the required depth
- Position the foundation frame in the trench at the correct level
- Backfill the trench with soil and compact to secure the frame
- Attach the Riga IIIs greenhouse structure to the foundation frame
This method provides a secure, stable anchor without the cost or permanence of a concrete foundation. The raised frame height also gives you additional interior headroom and growing depth compared to a ground-level installation.
Riga IIIs vs. Riga III — Which Foundation Frame Do You Need?
| Model | Foundation Frame | Price |
|---|---|---|
| Riga IIIs (smaller "S" variant) | This frame | $1,049 |
| Riga III (standard) | Riga III Foundation Frame | $1,299 |
The Riga IIIs is the shorter length variant of the Riga III series. Both share the same arch width and profile but differ in length — and each requires its own model-specific foundation frame. Make sure you order the frame that matches your exact greenhouse model.
Frequently Asked Questions
What is the difference between the Riga IIIs and Riga III foundation frames?
The Riga IIIs foundation frame ($1,049) is engineered for the shorter "S" variant of the Riga III series. The Riga III foundation frame ($1,299) is for the standard-length Riga III. Both use the same buried in-ground installation method but are sized to fit their respective greenhouse footprints. Order the frame that matches your exact model.
Is the foundation frame required for the Riga IIIs?
A proper foundation is strongly recommended for structural integrity, stability, and warranty compliance. The foundation frame is the recommended solution for soil or lawn installations. If you are installing on an existing concrete pad, you may not need this frame — contact us to confirm the right foundation approach for your site.
Does the foundation frame add headroom inside the greenhouse?
Yes — because the frame raises the greenhouse above ground level, you gain additional interior height compared to a ground-level installation. This is a meaningful benefit for tall growers or for hanging baskets and vertical growing setups.
How deep does the trench need to be?
The required trench depth depends on your local frost line and soil conditions. Refer to your Riga IIIs installation instructions or contact us for the recommended trench depth for your climate zone.
Can I install the foundation frame myself?
Yes — the installation process (dig trench, position frame, backfill, attach greenhouse) is designed for DIY completion. Having two people is recommended for frame positioning and alignment. Refer to your Riga IIIs installation instructions for specific guidance.
Why is free shipping only available when purchased with a greenhouse?
The foundation frame ships free when ordered together with a Riga IIIs greenhouse because it can be included in the same freight shipment. When ordered separately, it ships as a standalone item and an additional shipping charge applies due to its size and weight.