Earlybird delivery discount: Check out reductions available on this page. Take advantage now.
Now is the time to pick up an ex-display building during our annual sale. See remaining models here At LEAST 30% Off

Earlybird delivery discount: Check out reductions available on this page. Take advantage now.
Now is the time to pick up an ex-display building during our annual sale. See remaining models here At LEAST 30% Off

Earlybird delivery discount: Check out reductions available on this page. Take advantage now.
Now is the time to pick up an ex-display building during our annual sale. See remaining models here At LEAST 30% Off

Constructing a Perfect Base for Your Garden Office – Step by Step Guide

A sturdy foundation helps keep your garden office stable, level and damp-free. This detailed guide shows how to accomplish it in full.

The Ultimate Guide to Creating a Garden Office Foundation


Shows image of garden building

Garden offices are a must-have addition to any typical British garden. These sanctuaries allow you to appreciate the seasons in all their glory while also providing shelter from the sun, wind, and rain. They also offer the added benefit of working from home.

However, if you want your garden office to last, you must learn how to lay the foundation. Otherwise, it could decay from the ground up, collapse, or be destroyed by wind.

Fortunately, you will not need to learn how to build a foundation independently. This guide is here to help. It discusses the various types of bases for garden buildings, how to create them, who to employ for base construction, and how to repair and maintain your system. Everything you need is in one location.

Garden Office Bases.

Shows image of garden base

When adding a garden building, bases are critical for stability and longevity. Without a stable foundation, the structure will shift and settle, potentially with long-term effects.

Bases provide a flat platform for the building to sit on, evenly distributing weight and lowering the likelihood of structural concerns. They also help raise the structure above ground, reducing moisture exposure and preventing decay and disintegration.

Investing in a solid foundation is essential for the garden office’s durability and endurance. They nevertheless need a foundation, a stable framework that permits them to function endlessly. They cannot survive without it.


The primary purpose of foundation design is to ensure structural longevity. The construction prevents ground moisture from accessing the office’s wooden flooring and walls.

Keeping the structure dry lowers the chances of degradation, mildew, and structural distortion. It also makes the structure simpler to maintain.

Level ground

Bases also provide level ground for garden offices. Professionals design these to give a smooth surface that allows the building to stand straight.

Without bases, these buildings would be entirely dependent on the flatness of the ground underneath them. The ground must remain level throughout the process to keep the construction straight and exact.

The bases prevent one side of the garden office from sitting lower or at a different angle than the other. This holds the structure upright, similar to traditional housing foundations.


Lastly, bases provide stability. Hard materials, such as concrete or pavement slabs, provide structural support when people move around inside.

Concrete foundation

Garden buildings need a variety of bases to stay level and stable. Your priorities, the weather, and other considerations will all influence your selection.

Below are the three basic base types. We examine their nature and the benefits and drawbacks associated with each. By the end, you should have acquired enough information to choose the best choice for your project.

Concrete foundation

Shows image of concrete slab base

Concrete foundations are solid slabs buried in the ground (often during excavation). Installers use special tools to ensure that the material sets smoothly and provides a solid foundation for the garden office to stand on.


  • Extremely stable and durable. Concrete is a long-lasting material suited for outdoor applications in exposed places. It is beneficial for heavier outbuildings such as garden offices.
  • Long lifespan. Most concrete bases last for decades. (Some property owners still use concrete platforms created during WWII). Once built, it usually outlasts the structure it serves.
  • Has little maintenance requirements. Concrete bases do not require treatment. Once in place, maintenance is useful but not required.


  • Drainage concerns. Concrete slabs can gather rainwater beneath them, eventually seeping into the material via microscopic permeable holes.
  • The installation method is more complex. Professionals do not recommend DIY concrete base installation. Excavating, soil preparation, curling, and levelling are only a few of the many complex parts of construction.
  • Correcting flaws is tough since it involves breaking up and restoring concrete.
  • Costly. Concrete bases are more expensive than alternatives (because of materials and workmanship expenses).
  • The installation process is time-consuming. Summer house owners must allow the concrete to be completely set before placing the building on top. This process can take days or weeks, depending on the product.

Paving Slab Base

Shows image of paving slab base

Paving slab bases are simpler, with slabs placed on crushed materials such as gravel or without a sub-base (not advised). These provide many homes with a nice appearance without the strength of concrete.


  • Easy to modify. Installers are not required to set paving slab bases correctly the first time. DIYers and professionals can test each stone and the aggregate beneath it to ensure everything fits properly.
  • Built-in adjustability. Owners can shift pavement slabs over time in response to ground density and sinking. Subbases are adjusted for paver relaying.
  • Faster installation. No specific tools or equipment are required to install an aggregate foundation or paving slab. Groundwork is still required, although it is far simpler than concrete.


  • Less dependable. Paving slabs can slip and quiver as the sub-base shifts, making garden structures unstable.
  • Higher maintenance. Concrete foundations stay stable throughout their lifespan, whereas pavement slabs may move or change height. Depending on the surrounding landscape, owners may need to re-level paving slab bases regularly, increasing maintenance needs.
  • Sub-base drainage issues. Paving slab aggregates may hinder water from properly draining into the surrounding soil (especially as they age). Sub-bases may need to be replaced (this entails raising the slabs, filling the excavated area, and replacing them).

Timber sub-frame base


Shows image of timber subframe base

Timber sub-frame bases are built with treated wooden beams on concrete pads or foundations. Garden offices sit on top of these, reducing the likelihood of moisture damage.

Timber sub-frame bases were popular in the past because they were easily accessible. However, it requires the creation of a concrete support structure.


  • Suitable for moderate soil. Wood bases weigh less and perform better in softer soils.
  • It is cost-effective. Summer house owners can add hardwood beams to their existing concrete work, considerably lowering installation costs.
  • Easy to install. Timber subframes do not require any curing or drying time.


  • Concrete should be pre-installed. Most timber subframes require pre-installed concrete pads or pillars to work effectively. Others require bricks to protect against the underlying dirt.
  • Poor durability. Timber is less durable than concrete because it is prone to moisture, rot, and burrowing insects.
  • High upkeep is necessary. Timber sub-bases require regular preservative treatment. Accessing individual beams beneath a garden office to perform this maintenance can be challenging.
  • Limited weight capacity. Wood beams are less durable than concrete and stone pavers, limiting their ability to sustain large garden constructions above them.

1st Choice’s ‘No Concrete’ Answer with Timber Subframe Bases

Standard Timber Subframe Base
This is the ideal solution for garden sheds, workshops and garden rooms when the intended site is relatively level or when a base is needed to sit atop and level an existing concrete base; it is also very popular when access to the property is restricted or when people wish to avoid the disruption of concrete base construction.

A sturdy frame is constructed using 100mm x 47mm structurally graded C24 spruce, subjected to an enhanced pressure treatment process to improve its life.

To increase rigidity, cross members are placed at centres between 35cm and 42cm (14” and 16 1/2”) and noggins when the base’s width is greater than 1.5m (5’). The frame is levelled and supported on indestructible recycled plastic ground posts, which are manually driven into the ground.

When the timber subframe is sat atop a concrete base these plastic posts are not required and chunky timber feet are used in lieu when levelling is required.

Heavy Duty Timber Subframe Base
Whilst our standard timber subframe bases are ideal for most situations, sometimes something more robust is called upon. This may be because the building is particularly large or heavy, the plan is to store a large amount of weight within the building, or simply because the ground on which the base is situated has more than a minor slope.

Whatever the reason, our installation team will upgrade the standard specification by upgrading the fixings to coach screws, digging out each post and concreting these into the ground and, where necessary, fitting diagonal braces to add rigidity to the joint between the ground post and the rame (when the base is elevated out of the ground). A wise upgrade when ordering a log cabin or other larger building; please ask our sales advisors for guidance if you are unsure.

You can find more details here.

When deciding on a base for your garden room, consider these advantages and disadvantages. Manufacturers will usually advise you which base type works best with their items.

A Step-by-Step Guide to Creating a Garden Building Base

Some homeowners engage specialists to construct garden bases, but if you are brave enough, you can do it yourself.

This method can be tough to master, so carefully follow the instructions provided. Deviating from them may endanger your garden office (or any other garden structure you construct on top).

Site clearance and preparation

The first step is to clear and prepare the area for installation. Getting this right increases the chances of establishing a solid foundation.

Start by cleaning the area. Remove anything that may get in the way of construction. For example, make sure to delete

  • grass
  • Cannabis.
  • Shrubs.
  • Rocks
  • Bricks.
  • Garden waste.
  • Compost.

The site should be empty of all but earth. If you want your garden office to sit in your garden, don’t remove too much grass. Excessive removal can be detrimental to your appearance.

After you’ve cleared the area, measure the base’s outline. Marking where it will go exposes its imprint on your garden.

Most do-it-yourselfers utilise twine and stakes. You can also mark the region with paint, but ensure it cures first to safeguard the essential components.

Always trace the base’s outline with a measuring tape. When selecting a footprint, consider the shape of your garden office. The majority of units are square or rectangular, although a handful are hexagonal or octagonal, which makes base building more difficult.

Levelling Ground

The next step is to level the exposed land. Making it flat makes the foundation easier to lay.

Most terrain is not perfectly level; therefore, you must consider the slope. Identifying minor peaks and dips lets you determine whether you need complete levelling.

You may notice that the ground is rugged but mostly level. Some areas have steep slopes that are difficult to level.

If the location has a steep inclination, consider building your home office elsewhere. Slope removal entails substantial excavation, and new retaining walls may be needed.

Soil must be added and removed to level slopes for garden buildings. Unless there is a large incline, the levelled area should be the same height as the surrounding area.

Use a shovel or rake to disperse soil evenly across the land for easy chores. Removing soil from one spot and relocating it to another may result in a level surface.

Machine rentals are perfect for large businesses. Diggers and tractors can level the ground using various scoops and attachments.

Ground levelling is a laborious process that might take a long time. Be patient with it. If you aren’t satisfied with the levels after one day, return the next day and try again with a new viewpoint.

When levelling, make sure that the soil stays within your defined border. If possible, avoid removing soil from other spots.

Finally, ensure that the levelling does not adversely affect drainage near the site. Do not level terrain that slopes towards an existing structure.

When preparing land, consider where the water flows. Make sure it flows away from existing structures and into suitable drainage systems.

Skilled garden-building base installers can level the soil and create a gentle slope in the correct direction. Only if you are capable and motivated should you attempt this.

Installing Weed Membrane

Weed membranes may be required in some circumstances. Putting it down prevents stubborn weeds from penetrating the soil and degrading the subbase.

Do not use typical weed membranes. These may not be robust or resilient enough to safeguard your garden structure. Use items intended exclusively for summer cottages and install them over the base area’s boundaries using the available fittings.

Allow the earth to compress.

After you’ve finished levelling, allow the soil to settle. Allowing it to squash reduces air pockets while increasing stability.

Unfortunately, passive soil compaction might take several weeks or months. To work faster, professionals use a range of compaction equipment. These constantly press into the ground, holding it in place.

Compaction equipment can rapidly detect differing densities in your soil foundation. If you see any progress, add soil, rake it over, and keep compacting.

When compacting, be methodical. Begin in one corner and work in lines to cover the designated area. Continue until the soil has stopped moving.

If you do not own any compaction tools, you can rent them from a local builder’s yard or equipment store. Compacting land to an acceptable density should take at most a day.

Add the base material.

After you’ve prepared your garden base, the next step is to add the appropriate elements. The three needed supplies are mentioned below, along with installation instructions.

The Concrete Base

Concrete preparation is the initial step in constructing a concrete foundation. For a small garden, you can use ready-mix concrete (produced in a mixer) or bagged cement.

You will also need:

  • A long spirit level.
  • Edging Board
  • Crushed rock sub-base.
  • Mixing tools
  • Wheelbarrow.
  • Shovel.
  • Wear goggles and gloves.

Excavating for concrete foundations is generally unnecessary, but you may have to dig through the dirt.

If you have damp soil or plan to build a large structure on the foundation, most experts recommend excavating down 100mm (approximately 5 inches). After the excavation is complete, you can add the aggregate. It will serve as a base drainage system, keeping rising water from creating flooding or other problems.

Formwork may be necessary for large concrete-based projects. Edging boards define the base’s limits and hold the concrete in place as it hardens.

After these preparations, it is time to pour the concrete. Follow the manufacturer’s instructions (concrete mixing methods vary widely between brands).

After mixing, pour the concrete quickly. If you leave it too long, it may solidify before reaching the base.

Pour the concrete into the designated base area. It will spread to fill up the available area. (If it’s too thick, it won’t spread; therefore, make a fresh batch.)

For large bases, use a concrete pump. These transport enormous amounts of material from truck to nozzle while eliminating the need for wheelbarrows and other interim solutions.

After pouring the concrete, level it to ensure a smooth finish. Most do-it-yourselfers utilise a screed, which is a simple portable equipment. Rake it over to make sure the concrete is level with any edge boards you have.

The concrete should slope slightly away from nearby buildings to guarantee proper drainage. A flat surface may lead to water pooling or runoff in the wrong direction.

The final stage involves finishing and curing. Concrete needs time to set correctly.

Most goods take 24 to 48 hours to dry. However, some concretes may take up to 28 days to reach full strength.

While the concrete hardens, some professionals build vacation homes on top of it. This procedure is problematic because the weight of the building can leave markings on the concrete. Always follow the manufacturer’s guidelines. Please do not use a concrete base until it is entirely ready.

Paving Slab Base

Shows image of paving slab base

Installing a paving slab base requires a special approach. The first step, much like with concrete, is to gather your ingredients. You will need:

  • Paving slabs
  • Crushed stone.
  • Sharp sand.
  • The Spiritual Level.
  • A rubber mallet.
  • A mortar-like combo.

The first step is to lay the sub-base when you have all the necessary materials. This phase is nearly comparable to concrete. To begin, excavate the ground to a depth of 100mm and fill it with hardcore material suitable for the weight and size of the summerhouse.

Next, add the sharp sand. It creates a soft, consistent bedding material for the pavers. (Concrete does not require this step because it can fill gaps around the aggregate).

Finally, place the slabs. Professionals typically start in one corner and work their way around.

When placing each slab:

  • Make sure it is level with the spirit level.
  • Check that it doesn’t wobble from side to side.
  • Ensure it matches your desired pattern or impact.

If a slab is not level, use a rubber mallet to move it into the proper position. If necessary, add more sharp sand beneath or around the slab to improve its stability.

The second stage is to “join the slabs,” which entails closing gaps between them with material like mortar. Don’t build the complex yourself. Instead, utilise the one provided by the vendor.

A slab breaker may be required to cut slabs into the appropriate shape. They used diamond-edged cutters to shatter the granite into tiny shards.

If you need more clarification on this phase, hire an expert to pre-cut slabs based on your foundation plan. This method lowers risk while increasing the likelihood of a successful outcome.

Timber Subframe Bases.

Timber subframe bases are the easiest to build and require the least technical equipment. To construct a timber subframe foundation, you will require:

  • Use pressure-treated timber beams suitable for the weight of your structure.
  • Concrete foundation blocks
  • Screws are provided.
  • Drilling is taking place.
  • The spiritual level.
  • Saw.
  • Sharp sand.

If you are unsure whether the timber is appropriate for your garden office, consult a timber trader. Experts can recommend the best outdoor wooden beams to utilise.

Concrete blocks or pads are first inserted when constructing the wooden subframe foundation. If necessary, place them on the ground and position them correctly to support the construction. Make sure they are level with your spirit level; if not, add some sharp sand.

Next, cut and install the timber beams (unless you purchased pre-cut timber). Use a saw to cut the wood to the required length. Using a drill and screws, attach the wood pieces according to your design.

Finally, set the completed foundation onto the concrete pad. Use L-shaped metal brackets and secure them using concrete-specific screws.

Who created the base?

Shows image of professional concrete base

There are two ways to build a foundation for your garden office:

  • Do it yourself with the support of friends.
  • Professional “no-nonsense” professionals provide peace of mind.

Building your own foundation is less expensive initially, but the risks are more significant. While your friends may appear capable, the mistakes they make now could cost you later.

Individuals with extensive building or construction experience should create the foundation for their garden building. If you’ve done this type of work before, there’s no reason you can’t use the same concepts on your property.

All three bases mentioned above demand specialised construction expertise. Concrete variations, on the other hand, are undeniably the most difficult because they require specialised equipment and levelling and curing knowledge.

If you already have concrete pillars or pads (or supporting masonry), installing a timber sub-base may be a DIY project. However, you must strictly adhere to the layout rules and use the specified beams (heat and pressure-treated).

You’ll benefit from a professional “no-nonsense” approach if you’ve never built a garden office foundation. This strategy is more expensive initially, but it may save you money in the long run if you make mistakes.

Professionals, for example, provide their skills to construction projects. Unlike do-it-yourselfers, they have years of expertise performing similar tasks and are familiar with all aspects of site preparation.

Better still, they can do the assignment faster. Professionals spend less time on easy tasks and work more quickly to complete projects.

Furthermore, hiring specialists rather than buddies is more likely to produce positive results. Specialists must stand behind their work and deliver high-quality results to be respected. Someone you know in the community does not need to have the same qualifications.

Finally, employing pros is safer. Experts remove paving slabs and pour concrete daily, so they know the risks. Amateurs may not. DIY tasks can cause splinters, stumbles, falls, and injuries to the back, neck, hand, and toe.

How Can First Choice Help You?

We at 1st Choice specialise in offering an extensive collection of quality timber, concrete and metal buildings, so you can be assured that you will find your ideal building with minimal fuss. There are occasions, however, when other specialists are required to complete your project, and our years of experience in this field mean that we have built up some valuable connections with reliable tradespeople whom we have put forward here for your consideration.

Whilst the individual tradespeople are independent of us (thus keeping the pricing as low as possible), we are happy to liaise with them to make arrangements on your behalf. We, therefore, take a deposit, which is passed along to them with your order. They will collect the balance outstanding upon completion of the works and leave you with an invoice for your records.

Prices quoted presume a suitable, accessible work site within 50 miles of our display area near Woking. If your site is further afield or access is poor, the standard quoted prices may be subject to an additional charge. You can find more details here.

How to Maintain and Repair Garden Building Bases

Garden building foundations are often rather sturdy. However, they still require routine maintenance.

So what should you do? Let us find out.

Regular inspections occur.

Regular inspections are essential to ensure optimal upkeep. Checking your base for damage prevents minor issues from escalating.

During an inspection, check for the following symptoms of deterioration or damage.

  • Damp places persist even in warm weather or after storms. (Damp regions appear black on concrete and wood).
  • Concrete pads or beams may wobble or shift when touched.
  • There are cracks in the base.
  • Wooden items may deteriorate.
  • Adjust the bases to a different angle than initially established. (Bases can occasionally shift owing to ground movement or subsidence).
  • The dirt is approaching the garden office foundation.
  • Cracks appear in the jointing material of paver slab bases.
  • Uneven paver slabs.
  • Excessive aggregate or sand washing out from under the foundation (often in the direction of draining water).

Most testing will uncover no problems with your foundations, provided they are correctly developed. However, it is vital to monitor it because errors can be costly to fix if not addressed.

Repaired cracks and damage.

Cracks in foundations are cause for alarm. However, the steps you take should be proportional to the gravity of the situation.


Minor hairline fractures in concrete are rarely cause for concern. Document them and intervene if they escalate.

Concrete fractures of less than 6mm (approximately a quarter of an inch) must be filled. Leaving them can cause freeze-thaw weathering, in which ice freezes within and expands, pushing them apart. This behaviour may eventually cause structural harm.

Remove any debris, such as leaves, soil, or twigs, to fix a concrete fracture. Next, apply the concrete filler. Ensure that the filler is completely inserted into the crack. Filling it completely prevents dangerous water infiltration (which causes the previously described freeze-thaw damage).

Most professionals advocate applying flexible sealants to the repaired area once it has dried. These can expand and contract with the underlying crack and filler, sealing the patch.

The paving slab

Paving slab bases may also crack. The severity of the damage affects the sort of repair you use, just as it does with concrete bases.

To level uneven slabs, place or remove sand beneath each paver. However, accessing them may require disassembling your garden office from its pedestal.

Replace or repair any badly damaged pavers. With proper jointing, a single fractured paver can be separated into two slabs. Simply make sure it is not weight-bearing.

If you detect several cracks in your paving slab base, this could indicate earth movement or subsidence. Unfortunately, this issue may necessitate a complete reinstall on more firm soil.

Timber Subframe Bases.

Finally, timber sub-frame bases may crack under certain conditions. You will need to fix any non-surface damage.

If you see a slight break in a beam, sand it to assess its depth. Superficial cracks sometimes appear to be more severe than they are.

If the crack spreads, replace the beam. Unscrew it from the structure and replace it with a new piece of wood that meets your standards.

Cracks might develop due to degradation or insect infestation. If this happens, look for signs of humidity and insect damage. Also, confirm that the beams were appropriately treated before installation. Most insects avoid preservative-treated timber beams.

Preventing Water Damage.

Stopping water damage requires preventing it from entering your base in the first place. Consider the beginning of the construction method.

The most straightforward technique for preventing water damage is to design the base to slope in one direction away from your buildings. A small slope helps water drain while providing a solid foundation. As previously stated, maintaining a modest angle while providing a stable foundation for your garden office is difficult, so many homeowners seek professional assistance.

You can also avoid water damage by ensuring sufficient drainage around your structure. Using the proper sub-base, drain lines, and gullies will allow your garden office to drain excess water during a downpour. During your inspections, look for drainage that runs onto neighbouring properties and rivers. Slowing runoff can prevent flooding and keep water from entering the excavated area.

Finally, consider the materials you use. Most professionals use waterproof concrete for their foundations. These compounds prevent porosity holes from forming during the curing process, and waterproofing keeps moisture out of the substance, even in standing water.

Wood treatments can also help to protect against water damage. Repeat this every several years.


Shows image of heavy duty base

After reading this guide, you should better understand the importance of a solid foundation for your garden office. The structure above it must remain stable, level, and free of dampness.

However, achieving it right necessitates understanding what you’re doing. If you have doubts, consult an expert.

If you’re considering building a garden office at your home, consider the best foundation. In some cases, concrete may be preferred over paving slabs. Also, consider the weight of your garden building and the soil type.

What are you waiting for if you still need to start your garden office base project? Begin your project today and create your own breathtaking hideaway.

Frequently Asked Questions (FAQ) Garden Office Bases

No results!
  • Does a garden office need foundations?

    A garden office typically requires a solid foundation to ensure stability and longevity. The foundation can be in the form of concrete pads or strip foundations, depending on the size and weight of the structure. Without adequate foundations, the garden office may be prone to movement, instability, and potential damage over time. Properly constructed foundations provide a level and secure base for the office, helping to prevent issues such as sinking or shifting. It is essential to consult a professional to determine the most suitable foundation type for your specific garden office requirements.
  • How deep should a garden office foundation be?

    The depth of a garden office foundation should typically be at least 75 - 125 centimeters for stability and durability. This depth helps prevent shifting or sinking of the structure over time, especially in areas with varying soil conditions. A deeper foundation may be necessary in regions prone to frost or with particularly soft or unstable soil. Prior to construction, it is advisable to consult with a structural engineer to determine the specific depth required based on the site's characteristics.
  • What is the best base for a garden office?

    A solid concrete base is the best foundation for a garden office due to its durability and stability. Concrete provides a level surface for the structure, preventing any shifting or sinking over time. Additionally, a concrete base offers excellent support for the weight of the office and its contents, ensuring structural integrity. This type of foundation is also resistant to moisture and pests, minimizing the risk of damage to the office over the years. Overall, a concrete base is the optimal choice for a garden office, offering long-term reliability and peace of mind.

About Author:

Robin Antill is an established authority in the field of quality garden building manufacturing, boasting over four decades of experience. Having founded Titan Garden Buildings in 1979, he demonstrated a commitment to excellence from the outset by moving away from subpar materials and embarking on crafting buildings of superior quality.

His lineage of craftsmanship, traced back to his father and grandfather's business in Cleethorpes, underscores his dedication to quality and customer satisfaction. Robin's son, Craig, who joined the business in 1990, brings additional expertise, having honed his skills at Guildford College in joinery.

Together, they elevated Titan Garden Buildings, which eventually evolved into 1st Choice Leisure Buildings. Their enduring focus on premium materials, top-notch manufacturing, and unparalleled customer service, along with Craig's digital acumen in creating the company's online presence, showcase their expertise and reliability in the industry.

Robin’s expertise was featured in Realtor.com, Homes&Gardens, The London Economic, and dozens other publications.

Woking Show Site
1st Choice Leisure Buildings
Woking Garden Buildings Show Site
Sutton Green Garden Centre,
Whitmoor Ln, Sutton Green,
Phone 01483 237550