Foundations for your SelectHaus glasshouses

Sturdy foundations are necessary to prevent subsidence or heaving. Here are the four best foundation options for a glasshouse structure, ranked by their suitability.​

 

1. Concrete Strip Foundation
 

This is the gold standard for a permanent, heavy timber glasshouse. Instead of pouring a massive, solid concrete slab, you dig a trench only under the perimeter walls.
 

• How it works: You dig a trench below your local frost line, fill it with concrete, and build a low brick or concrete block wall (a "plinth") up to ground level. The timber frame sits on top of this masonry plinth.
   

• Pros: Incredible structural stability; keeps the timber high and dry away from wet soil; allows you to keep natural soil inside for planting directly into the ground.
   

• Cons: Labor-intensive; requires excavation and concrete mixing.

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2. Poured Concrete Slab:

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A solid concrete pad that covers the entire footprint of the glasshouse. It acts as both the foundation and the final floor.

• How it works: You excavate 100–150mm of soil, lay down a compacted hardcore (gravel) base, build a wooden shuttering frame, and pour concrete over a steel mesh for reinforcement.
   

• Pros: Perfect level surface; completely eliminates weeds and burrowing pests; handles the glasshouse weight with absolute ease.
   

• Cons: Expensive; permanently seals the ground (you can only use raised beds or pots inside); requires a slight slope or drainage hole so watering doesn't pool inside.

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3. Concrete Pier / Ground Screw Foundation:

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​If you want to avoid pouring large amounts of concrete, a point-load foundation is an alternative.
 

• How it works: You dig deep holes at the corners and at 1.5-meter intervals along the perimeter, filling them with concrete to create "piers" (or you mechanically screw heavy-duty steel ground screws into the earth). The pressure-treated timber ring beam is then bolted to these points to support the glasshouse.

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• Minimal digging; great for uneven ground; allows for a natural dirt or gravel floor inside.

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4. Engineering Brick / Paver Base (Best for Small/Medium Models)

If your glasshouse is small or medium and your soil is firm and well-compacted, you can build a perimeter wall directly on a compacted aggregate base.
 

• How it works: Dig a shallow trench, pack it tightly with aggregate, lay a bed of mortar, and lay 2–3 courses of engineering bricks (which don't absorb water).
   

• Pros: Highly aesthetic; traditional look; good drainage.
   

• Cons: Susceptible to shifting if you have heavy clay soil that swells and shrinks with the seasons.
   

Critical Rules:
 

• Anchoring: A glasshouse can act like a sail in high winds. Ensure your frame is mechanically anchored into the concrete or brickwork using heavy-duty expansion bolts (like Dynabolts or masonry anchors).
   

• Leveling: Aim for a tolerance of less than 2mm across the entire span. If the foundation is out of level, the glass panes will not fit, or worse, they will shatter under stress later.