Buyer's Guide
Preparing Your Garden: What Base Do You Need for a Summer House?
Even the best craftsmanship will fail on a terrible foundation. Here's exactly what you need to know.
You are investing in a heavy-duty, bespoke timber building. But even the best craftsmanship in the world will fail if it is built on a terrible foundation.
If your base is unlevel, the timber frame of the summer house will eventually twist. Doors will drop, UPVC windows will bind, and the roof could warp. Any reputable installer building on-site will need a perfectly solid, level base before they start.
Here is exactly what you need to know to prepare your garden, depending on the size of your building and the layout of your land.
Summer house base options at a glance
The Concrete Slab (The Gold Standard)
For larger garden rooms, heavy-duty home offices, and especially home gyms, a solid concrete base is the ultimate foundation. It distributes massive amounts of weight evenly and guarantees a perfectly flat footprint.
Best for
The Pentrich, The Contemporary Executive, large Combi structures such as The Denby, and any building housing heavy equipment.
The rule
The concrete slab should be poured exactly to the footprint dimensions of your building (your supplier will provide these). It must be 100% level across the entire surface.
Keep in mind
Concrete needs time to cure before any build can go ahead, so this needs to be completed well in advance of your installation date.
Heavy Paving Slabs
If you are installing a standard-sized summer house or corner unit, a base made from heavy paving slabs is an excellent, cost-effective alternative to pouring wet concrete.
Best for
The Haven Corner Summerhouse, The Panoramic Octagon, and standard leisure rooms.
The rule
You cannot just throw slabs onto grass. You must dig out the topsoil, lay a compacted hardcore sub-base, and bed the slabs down on sand and cement to ensure they are completely level and won't sink over time.
Timber Frame & Ground Screws (For Slopes & Uneven Ground)
If your garden has a steep slope, or if you want to protect tree roots and avoid massive earthworks, a heavy-duty timber frame supported by steel ground screws or concrete pillars is the perfect solution.
Best for
Gardens with severe gradients, areas prone to flooding, or locations where access for a cement mixer is impossible.
The rule
The framework must be constructed using thick, pressure-treated timber (e.g. 4x2 or 6x2 C16 timber) to prevent bounce. Your supplier or installer can advise on the exact load-bearing requirements for your specific building.
Alternative option
The On-Site Timber Base (The Zero-Hassle Option)
Don't want the headache of hiring a separate contractor to lay concrete or slabs before we arrive? We offer a fully integrated, "done-for-you" solution.
If your garden is relatively firm but unlevel, or you simply want to avoid massive earthworks, our installation team can build a heavy-duty, levelled timber base for you on the exact day of delivery.
Best for
Customers who want a stress-free installation, gardens with slight gradients, or areas where you want to avoid pouring permanent concrete.
How it works
Before we erect your summer house, we construct a robust framework using thick, pressure-treated structural timber. We perfectly level this frame on your existing ground, guaranteeing your new building sits flawlessly flat and its structural integrity is protected.
The benefit
No waiting for groundworkers, no messy wet-trades in your garden, and the entire project—from base to roof—is completed by one expert team in a single booking.
What You Should NEVER Do
Avoid these mistakes to protect your investment and guarantee longevity.
Never build directly on grass or soil
The moisture will instantly rot the floor bearers, and the building will sink unevenly.
Never build on loose gravel without a retaining border
The gravel will shift under the weight of the building.
Never assume "close enough" is level
A 10mm drop on one side translates to a massive lean at the top of a 2.5m high building. Use a long spirit level!
Always ensure a stable, level, and appropriate base to protect your investment and guarantee longevity.
Need advice on your specific site?
It's worth getting site-specific advice before you commit. A good supplier will assess your site and tell you exactly what footprint and base type you need for your chosen summer house.
Request a Free Site Assessment & Quote