Complete Guide to Base Types for Garden Buildings: Garden Room, Log Cabin & Shed
03.02.2025
When it comes to installing garden buildings like sheds, garden rooms, or log cabins, choosing the right base is crucial and dependent on factors like the soil in your garden, how big the building is and your budget. A proper foundation ensures the stability, longevity, and functionality of your outdoor structure. This guide will walk you through the most popular base types, helping you make an informed decision for your garden project.

Why are garden bases important?
A well-built base protects your garden building against Ireland’s unpredictable weather and ensures your garden room stays stable and safe for years to come – soggy ground can be your worst nightmare without a strong, solid foundation in place. A proper foundation protects against ground movement which can result in uneven floors and cracked walls and also helps to keep moisture at bay, preventing issues like mould and rot that can plague poorly constructed buildings. It also helps with insulation, making your space comfortable year-round and potentially saving you money on energy costs. Plus, a good base ensures your garden room complies with local building regulations, giving you peace of mind that you won’t face legal issues down the line.
Guidelines for choosing the right base type for your building
Here are all the factors you need to consider before choosing which base type is most suitable for your garden build:
- Pick the perfect spot: Consider space, sunlight, intended use, property boundaries, and proximity to utilities.
- Know your ground: Check soil type, drainage, and ground level. A professional site survey can save headaches later.
- Size matters: Ensure your base is slightly larger than your building’s footprint for extra stability.
- Weight it up: Factor in the structure’s weight, including the furniture and equipment you’ll put inside.
- Rot-prone materials: Using materials that are susceptible to decay can compromise the foundation’s integrity and lead to problems later on.
- Inadequate depth: Foundations that are not deep enough may be vulnerable to ground movement and shifting over time.
- Keep it dry: Good drainage will prevent water from puddling around the foundation. Slope the ground away from your building to prevent water issues like rising damp, mould and structural instability.
- Stay legal: Check local planning rules to make sure you comply with planning permission requirements and local building regulations.
- Think long-term: Choose a base that’ll last. Concrete might cost more upfront but could save money over time.
- Level up: Whatever base you choose, make sure it’s perfectly level to avoid structural problems. Even a 1 cm discrepancy can cause massive problems for your garden structure.
- Insulate from below: Consider adding insulation to your base for a cosier garden room and lower heating bills in winter.
- Protect against damp: Use a damp-proof membrane to keep moisture at bay.
Since this is such an important step, it’s a good idea to take your time to make sure you consider all your options carefully. If you have any questions about choosing a suitable foundation for a Summerhouse24 garden building, please do reach out to the team who will be happy to offer you expert advice on the correct base to support your garden house.
Types of garden room foundations
Let’s take a look at the different types of foundation base you can use:
1. Ground screw base
Ground screw foundations can be installed quickly and efficiently, allowing you to start building your garden structure almost immediately. A professional ground screw company will first assess your site and recommend the best approach based on the current ground type. The installation involves driving heavy-duty metal screws deep into the ground to anchor your building securely. Once the screws are in place, a wooden foundation will be installed to create a level footing for the foundation beams.
2. Concrete slab base
A concrete slab base is a robust and versatile foundation option suitable for a wide range of garden structures in various sizes. While it’s one of the most durable choices, it does require more effort and investment due to its permanent nature.
How to install a concrete slab foundation?
To install a concrete slab base, first mark the area and excavate about 20cm deep, adding an extra 5 cm for the wooden boxing. Fill the area with 15cm of compacted gravel, then build a wooden frame to hold the concrete, ensuring it sits 4-5 cm above ground level for drainage. Cover the base with a damp-proof membrane, and for larger structures, include steel reinforcement mesh for added strength. Finally, pour the concrete into the frame, leveling it as you go. Allow it to harden for a few hours before removing the supports. Full curing will take about 3-4 days before you can begin constructing your garden build.
3. Strip foundations
Strip foundations offer a versatile and cost-effective solution for garden structures, providing a stable base without the expense of a full concrete slab.
How to install a strip foundation?
To install a strip foundation, start by marking the layout according to your building’s foundation plan, ensuring the strips are spaced approximately 90-100 cm apart. Excavate trenches that are 15-20 cm deep and 15cm wide. Fill these trenches with 10-15cm of compacted gravel or sub base material, then build wooden boxing that sits about 5 cm above ground level for ventilation.
For added strength, place steel reinforcement mesh in the center of each strip before pouring concrete. Mix and pour the concrete into the wooden boxes, leveling it as you go. Allow the concrete to set for a few hours, then clean the area between the strips and cover it with a damp-proof membrane or geotextile. Fill this space with gravel or sand to prevent grass growth. Finally, let the foundation cure for 2-3 days before starting construction on your garden building.
4. Paving slabs
Paving slab bases offer an excellent solution for small to medium-sized garden buildings, providing a straightforward, adaptable, and cost-effective foundation.
How to lay a paving slab foundation?
To install a paving slab base, begin by excavating an area 15-18cm deep. It’s a good idea to make the area slightly bigger than the area of your garden building so you have some dry ground around it. Cover the excavated area with a damp-proof membrane, followed by 15cm of gravel or MOT 1 granules, leveling and compacting it. Add a 3 cm layer of sand without compacting, then place the paving slabs with a 3mm gap between them, ensuring they are level. Finally, fill the gaps with sand and compact it firmly to create a stable foundation.
5. Adjustable riser pedestal or breeze blocks on to gravel
This affordable foundation option is ideal for sheds and garden rooms, particularly when leveling is needed on existing hard surfaces.
How to install a pedestal or breeze block foundation?
To install an adjustable riser pedestal foundation or one made of breeze blocks, begin by preparing the ground by excavating about 20cm deep and extending 10cm beyond the building’s footprint. Cover the area with a membrane to stop the grass growing and fill it with MOT 1 sub base or gravel, ensuring it is level and compacted. Place the adjustable risers or breeze blocks according to your foundation plan, typically spacing them 50-60cm apart. Assemble your foundation frame and carefully place it onto the risers/blocks, using a spirit level to ensure everything is perfectly aligned. Adjust the height of each pedestal if necessary by twisting the stem up or down until the entire structure is level. Finally, secure the foundation frame to the risers/blocks, creating a stable base for your garden building.
Foundation kit: a handy DIY alternative
If you’re looking for an easy, cost-effective foundation, the Summerhouse24 foundation kit might be the best choice. This DIY kit allows you to create a stable base for your garden building without the need for heavy equipment or complex materials. With a 20cm adjustment range, you can easily achieve a level surface in most gardens. The kit comes with everything you need, so there are no surprises halfway through the build that could derail your budget by running up your summer house costs unexpectedly. Whether you’re an experienced DIYer or just starting out, this foundation kit simplifies the installation process, making it accessible for anyone who can use a spirit level. If you’re not handy with tools, no problem – you can request that the Summerhouse24 team come and install your foundation and build your garden room for you.
The pros, cons, and costs of each type of foundation
TYPE OF BASE | PROS | CONS | APPROX COST |
Ground screw | Can be installed quickly, year-round, regardless of weather conditions. No concrete required. You can build immediately. | Best to use professional installation which costs more. They need to be 100% level to prevent tilting. May need to hire tools if you’re doing it yourself at an extra cost. | €50 – €120 per screw. €115 per m² for the timber frame base (free with Summerhouse24 garden buildings).¹ €250 – €350 labour costs per day depending on your area and company. |
Concrete slab | Durable and long-lasting. Suitable for structures of all sizes. Provides excellent stability and load-bearing capacity. Resistant to moisture and pests. | More expensive. Requires significant labour and time to install. Permanent, making future changes difficult. | With all materials and labour costs you could pay anything from €4k to €10k, or more, depending on the size you need.² Some companies do a per m² cost so it’s best to phone around – this company charges €210 per m² for example.³ Costs will be higher for bigger builds and in city areas like Dublin. |
Strip foundations | More affordable. Suitable for various garden building sizes. Easier to remove or modify for future projects. Provides good ventilation, reducing moisture issues. | Not ideal for sloped terrain. Requires precise planning and execution. | Approx €100 per m². It’s best to phone around and see which company do this type of foundation and compare the costs before deciding. |
Paving slabs | Easy to install. Relatively inexpensive. Simple to modify or extend. Attractive appearance. No concrete required. | Less stable for larger structures. May settle over time. Requires periodic maintenance. Not ideal for very uneven ground. | Costs vary depending on your material of choice but you are looking at a range of €35 to €150 per m². For example, a 35m² building might cost around €3k at the lowest price per m². ⁴ |
Riser pedestal/breeze blocks | Cost-effective. Easy to level on uneven surfaces. Quick installation. | Limited load-bearing capacity. May require periodic height adjustments. Not suitable for extremely unstable ground. | The pedestals are less than €5 each.⁵ The timber frame is around €115 per m². ¹Gravel is around €55 for a 1 ton bag.⁶ Breeze blocks are less than €2 per block. ⁷ |
Foundation kit | Cost-effective Easy DIY installation with basic tools. Adjustable for slightly uneven ground. Portable and reusable if relocating. Suitable for garden houses up to 45m². High weight bearing capacity. | May require additional effort for very uneven ground. Not as permanent as concrete foundations. | Between €1,910 to €3,140 depending on the size of the building you choose. |
Conclusion
Choosing the right foundation for your garden building is an important step that shouldn’t be rushed. Each foundation type has advantages tailored to different building types and site conditions. By considering factors such as soil type, building size, and your own DIY skills, you can make an informed decision that will support your structure effectively for years to come.
Sources:
- https://smartfoundations.ie/product-category/timber-frame-base/
- https://www.boards.ie/discussion/2058293026/shed-foundations-how-much-does-it-cost-to-install-a-concrete-base-for-your-shed
- https://sipkits.ie/product/concrete-slab/
- https://www.boards.ie/discussion/2058357503/2024-patio-cost-thoughts
- https://bpmsupplies.ie/collections/adjustable-pedestals?srsltid=AfmBOooxUTgQcOaUnnDR_QeB5dAPpx0yJ9zq6ltLIZVaSSHyMw9eMpc6
- https://howbertandmays.ie/products/grey-pebble-gravel-20mm-1-ton-bag?srsltid=AfmBOoomFyYva2qEEanD18VhQ1HRVaS8VDIoa4OisoQnd54wqXwV2Hdj
- https://mybuildingsupplies.ie/shop/building-supplies/concrete-masonry-cement/blocks/concrete-block-4inch-44-per-bale/
Categories:
GuidesWant to discuss over phone. Let us call back to you
If you need any additional info regarding any product, please fill in the below form and we will get back to you, usually the same or next working day.
Have any questions regarding some product?
If you need any additional info regarding any product, please send us your questions.