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Key Considerations for Building a Durable Base for Your Garden Shed

Building a good foundation for your shed will keep it stable, level, and damp-free. This extensive instruction explains how to accomplish it in detail.

The Ultimate Guide To Building A Base For A Garden Shed

Shows image of garden building

Garden sheds are a must-have feature for every typical British garden. These sanctuaries allow you to appreciate the seasons in all their glory while also giving shelter from the sun, wind, and rain.

However, if you want your shed to last, you must learn how to build its foundation. Otherwise, it may decay from the ground up, topple over, or succumb to the wind.

Fortunately, you will not have to learn how to build a garden shed base on your own. This guide is here to help. It discusses the numerous types of bases for garden buildings, how to make them, who to employ for base construction, and how to repair and maintain your installation. Everything you need is in one location.

Why Do Garden Sheds Need Bases?

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When building a garden construction, bases are critical for stability and endurance. Without a stable foundation, the structure will shift and settle, which can have long-term effects.

Bases give a flat platform for the garden shed to sit on, evenly distributing weight and lowering the likelihood of structural concerns. Bases also help to elevate the structure off the ground, which reduces moisture exposure and prevents decay and degradation.

A solid foundation is vital to the shed’s durability and lifespan. They still require a robust framework that will enable them to function endlessly. They cannot survive without it.

Longevity

The primary purpose of creating foundations is to ensure structural longevity. These constructions provide moisture protection, preventing ground moisture from penetrating the garden shed’s wood floors and walls.

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

Level Ground

Bases also offer level ground for wooden sheds. Professionals construct these to provide a smooth surface for erecting the garden shed.

Without bases, garden sheds would be entirely dependent on the flatness of the ground underneath them. The ground must be flat throughout the process to keep the building straight and level.

Bases prevent one side of the building from sitting lower or at a different angle than the others. This holds the structure upright, similar to typical housing foundations.

Stability.

Lastly, garden shed bases provide stability. Hard materials, such as concrete or pavement slabs, keep the structure stable as people walk about inside.

Bases for Garden Buildings

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

The three basic base types offered are listed below. We discuss them and the benefits and drawbacks of each. By the end, you should have gathered enough information to select the best solution for your project.

Concrete foundation

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Concrete foundations are solid slabs buried in the ground (often during excavation). Installers use specialised tools to ensure the material sets smoothly and forms a solid foundation for the garden shed.

Pros:

  • Exceptional stability and durability. Concrete is a long-lasting material suited for outdoor use in exposed places. It is advantageous for heavier outbuildings such as garden sheds.
  • Long lifespan. Most concrete bases last for decades. (Some property owners still use concrete platforms created during WWII). Once erected, it frequently outlasts the structure it serves.
  • Requires minor upkeep. Concrete bases do not require treatment. Once in place, maintenance is useful but not required.

Cons:

  • Drainage concerns. Concrete slabs can gather rainwater beneath them, eventually seeping into the substance due to tiny porous holes.
  • More complicated to install. Professionals do not recommend DIY concrete base installation. Excavating, soil preparation, curling, and levelling are only a few of the many complex phases involved in construction.
  • Correcting problems is tough since it involves breaking up and reinstalling the concrete.
  • Costly. Concrete bases are more expensive than alternatives (because of material and labour costs).
  • The installation process is time-consuming. garden shed owners must allow the concrete to be completely set before erecting the structure on top. This process can take days or weeks, depending on the product.

Paving Slab Base

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Paving slab bases are simpler and consist of slabs laid over crushed materials such as gravel or without a sub-base (not recommended). These give many homes a nice appearance without the sturdiness of concrete.

Pros:

  • Easy to modify. Installers are not required to lay paving slab bases properly the first time. DIYers and professionals can experiment with each stone and the aggregate beneath it until it all fits together.
  • Built-in adjustability. Owners can shift pavement slabs over time in response to ground density and sinking. Sub-bases can be adapted for paving bases.
  • Faster installation. No special tools or equipment are needed to install an aggregate foundation or paving slab. Groundwork is still required, but it is less complex than concrete.

Cons:

  • Less dependable. Paving slabs may slip and shake as the sub-base shifts, making garden structures less stable.
  • Higher maintenance. Concrete bases are stable throughout their lifespan, whereas pavement slabs may migrate or alter 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 require replacement (which includes elevating the slabs, refilling the excavated area, and replacing them).

Timber sub-frame base

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

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

Pros:

  • Ideal for mild soils. Wood bases weigh less and are better suited to softer soils.
  • It’s cost-effective. garden shed 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.

Cons:

  • Concrete must, ideally, be pre-installed. Most timber subframes require pre-installed concrete pads or pillars to work effectively. Others require bricks to provide a barrier against the underlying dirt.
  • Poor durability. Timber is less durable than concrete because it is prone to moisture, rot, and burrowing insects.
  • High maintenance requirements. Timber sub-bases require regular preservative treatment. Accessing individual beams beneath a summer home to perform this maintenance can be challenging.
  • Limited weight capacity. Wood beams are less durable than concrete and stone pavings, 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 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 instead 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 need more clarification.

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.

Step-by-Step Instructions for Building a Garden Building Base

Some homeowners hire specialists to construct garden bases, but if you’re brave enough, you can do it yourself.

This method can be challenging to master, so rigorously follow the instructions provided. Deviating from them could jeopardise your garden shed (or any other garden construction you place on top).

Site clearance and preparation

The first step is to clear and prepare the area for installation. Getting this right increases the likelihood of building a long-lasting foundation.

Begin by cleaning the space. Remove anything that could get in the way of construction. For example, be sure to eliminate:

  • Grass
  • Weed.
  • Shrubs.
  • Rocks
  • Bricks.
  • Garden waste.
  • Compost.

The site should be empty of anything but earth. Only remove a little grass if you want your garden shed to sit on your lawn. Taking away too much can jeopardise 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 DIYers combine string and stakes. You can also label the area with paint, but ensure it dries first to avoid damaging the basic components.

Always use a measuring tape to trace the outline of the base. When choosing a footprint, consider the shape of your garden shed. Most units are square or rectangular, but some are hexagonal or octagonal, making base building more difficult.

Ground Levelling

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

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 note that the terrain is bumpy yet mostly level. Other patches have steep slopes that are more difficult to level.

If the location has a steep inclination, consider building your summer cottage 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 it is on a steep slope, the levelled area should be the same height as the surrounding area.

Use a shovel or rake to spread soil evenly across the land for minor operations. Removing soil from one spot and putting it in another might create a more level surface.

Machine rentals are recommended for larger businesses. Diggers and tractors can level land using a variety of scoops and attachments.

Ground levelling is a complex operation that might take a long time. Be patient with it. If you aren’t satisfied with the levels after one day, come back the next and try again with fresh eyes.

When levelling, ensure the soil stays within your defined border. Avoid removing soil from other areas if possible.

Finally, the levelling should not negatively impact drainage near the site. Do not level terrain that slopes towards an existing building.

When preparing land, consider where the water flows. Check that it flows away from existing structures and into the proper drainage systems.

Skilled garden-building base installers can level the land to create a slope in the correct direction. However, you should only do this if you are capable and motivated to do so.

Installation of Weed Membrane

Weed membrane may be necessary in exceptional circumstances. Putting it down prevents stubborn weeds from entering the soil and ruining the subbase.

Do not use regular weed membranes. These may not be robust or resilient enough to protect your garden structure. Use items explicitly developed for garden sheds and install them over the base area’s boundaries with the supplied fittings.

Allow the earth to compress.

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

Unfortunately, passive soil compaction might take several weeks or months. To work faster, professionals use several compaction devices. These constantly press into the earth, pressing it into place.

Compaction equipment can quickly 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 move in lines until you’ve covered the marked 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 appropriate density should take no more than a day.

Add the base material.

After preparing your garden base, the next step is to add the basic materials. Here are the three basic materials and how to install them.

The Concrete Base

Concrete preparation is the initial step in constructing a concrete foundation. You can use ready-mix concrete (mixed in a mixer) or bagged concrete for a small garden.

You will also need:

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

Excavation for concrete bases is not usually required, so you may have to dig through the dirt.

Most experts recommend digging down 100mm (approximately 5 inches) if you have damp soil or want to build a substantial structure on the base. 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 sizeable concrete base installations. Edging boards define the base’s limits and hold the concrete in place as it hardens.

Following these preparations, it’s time to pour the concrete. Mix according to the manufacturer’s instructions (concrete mixing differs significantly between brands).

Once mixed, pour the concrete quickly. Leaving it too long may cause it to set before penetrating the base.

Pour the concrete onto the designated base area. It will spread to fill the available space. (If it is too thick, it will not spread, so prepare a new batch.)

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

After pouring the concrete, level it to get a smooth surface. Most do-it-yourselfers use a screed, which is a simple portable tool. Rake it over to ensure that the concrete is level with your edge boards (if using any).

The concrete should slope slightly away from your main buildings to guarantee proper drainage. A perfectly level surface may result in water pooling or runoff in the wrong direction.

The last stage is to finish and cure. Concrete needs time to set correctly.

Most products need 24 to 48 hours to dry. However, some concretes may require up to 28 days to reach full strength.

While the concrete cures, some specialists build on top of it. This approach is risky since the structure’s weight may leave impressions on the concrete. Always follow the manufacturer’s instructions. Please do not use a concrete base until it is ready.

Paving Slab Base

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Installing a paving slab base requires a different approach. The first step, as with concrete, is gathering your ingredients. You will need:

  • Paving slabs
  • Crushed stone.
  • Sharp sand.
  • Spiritual level.
  • A rubber mallet
  • A mortar-like mixture.

When you have the supplies, the first step is to lay the sub-base. This phase is nearly comparable to concrete. To begin, excavate the ground to a depth of 100mm and fill it with hardcore suitable for the weight and dimensions of the garden shed.

Next, add the sharp sand. This creates a soft and even bedding material for the paving. (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 laying each slab:

  • Ensure it’s even with the spirit level.
  • Check that it doesn’t wobble from side to side.
  • Ensure it reflects the overall pattern or impact you want to create.

If a slab is not level, push it into the proper position with a rubber mallet. If needed, add more sharp sand underneath or around the slab to increase its stability.

The following technique is to “join the slabs,” which entails filling the gaps between them with something similar to mortar. Don’t mix the mortar yourself; instead, use the one provided by the vendor.

You may need to use a slab breaker to cut slabs into the right shape. They use diamond-edged cutters to hew into the rock, breaking it into smaller 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 simplest to build and require the least technical equipment. To build a timber subframe foundation, you will require the following:

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

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

The concrete blocks or pads are laid first during the timber sub-frame base installation. If you haven’t already, you’ll need to install them in the ground and position them correctly to support the construction. Make sure they are level with your spirit level; if not, add 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 lengths. Using a drill and screws, assemble 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 builds the base?

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

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

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

Individuals with extensive building or construction experience should design bases for their workshops. If you’ve done this type of work before, there’s no reason you can’t apply the same concepts to your property.

All three bases mentioned above demand expert construction knowledge. Concrete foundations are the most complicated because they require specialised equipment, 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 rigorously adhere to the layout ideas and use the appropriate beams (heat and pressure-treated).

You could benefit from a professional “no-nonsense” approach if you’ve never built a 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 understand all aspects of site preparation.

Better still, they can complete the task 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 is not required to meet the same requirements.

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

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 many 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.

Tips for Maintaining and Repairing 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.

Inspections should happen regularly.

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 indicators of deterioration or disrepair.

  • Damp places persist even in warm weather or after storms have passed. (Damp spots will seem darker on concrete and wood).
  • Concrete pads or beams that wobble or shift upon touch.
  • There are cracks in the base.
  • Wooden things can rot.
  • Position bases at a different angle than originally set. (Bases can occasionally shift owing to ground movement or subsidence).
  • The soil is pushing on the garden shed’s foundation.
  • Cracks or cracks in jointing material of paving slab bases.
  • Uneven paving slabs.
  • Excessive aggregate or sand washing out from under the foundation (often in the direction of draining water).

Most tests will find no problems with your base, provided it is adequately developed. However, keeping an eye on it is vital because faults can be costly to remedy if not addressed.

Repairing cracks and damage.
Cracks in summerhouse foundations are cause for alarm. However, the steps you take should be appropriate for the gravity of the situation.

Concrete

Minor hairline fractures in concrete are typically nothing to worry about. Record them and take action if they worsen.

However, concrete fractures under 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. Over time, this process may cause structural damage.

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

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.

Paving slab

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

To rectify uneven slabs, add or remove sand beneath each paving. However, accessing them may require removing your garden shed from its pedestal.

Replace and repair any badly damaged pavings. A single fractured paving can be separated into two slabs with proper jointing. Make sure it’s not load-bearing.

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

Timber Subframe Bases.

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

If you detect a slight crack in a beam, sand it to see how deep it goes. 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 can form due to degradation or insect infestation. If this occurs, look for signs of humidity and insect damage. Also, ensure the beams were adequately treated before installation. Most insects avoid preservative-coated timber beams.

Water damage prevention

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

The most straightforward approach to prevent water damage is to design the base to slope in one direction away from your property. A slight slope helps water to drain while providing a solid foundation. As previously stated, creating a shallow angle while providing a sturdy foundation for your garden shed is difficult, so many homeowners seek professional assistance.

You can also avoid water damage by ensuring adequate drainage around your building. Using the proper subbase, drain lines, and gullies will allow your garden shed to drain extra water during rainstorms. During your checks, look for drainage that runs into neighbouring properties and rivers. Slowing runoff can help 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 substances prevent porosity holes from forming during the curing process, and waterproofing keeps moisture out of the substance, even in standing water.

Wood treatment can also assist in avoiding water damage. Repeat this every several years.

Conclusion

Shows image of heavy duty base

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

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

If you’re thinking of building a garden shed in your garden, consider the best foundation. In some cases, concrete may be preferred over paving slabs. Consider both the weight of your garden structure and the type of soil.

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

Frequently Asked Questions (FAQ) Garden Sheds

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  • Can you put a shed on paving slabs?

    Yes, you can put a shed on paving slabs. It is important to ensure that the paving slabs are level and stable to provide a solid foundation for the shed. By placing the shed directly on the paving slabs, you can create a sturdy and durable base that will help protect the shed from moisture and ground moisture. This method can also help prolong the life of the shed and provide a secure structure for storage or other purposes
  • Do garden sheds need a base?

    Garden sheds require a solid base to ensure stability and durability. A base provides a level surface for the shed to sit on, preventing it from sinking into the ground over time. It also helps to keep the shed level and secure, reducing the risk of damage from shifting or uneven ground. Additionally, a base helps to improve ventilation under the shed, reducing the risk of moisture buildup and rot. In summary, a base is essential for ensuring the longevity and performance of a garden shed.
  • What is the best base for a garden shed?

    Concrete makes the best base for a garden shed. It provides a stable and durable foundation that can withstand various weather conditions. Concrete also prevents moisture from seeping into the shed, protecting its contents. Additionally, a concrete base requires minimal maintenance and is long-lasting, ensuring the shed remains secure and stable for years to come.

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,
Guildford,
GU4 7QA
Phone 01483 237550