Techniques That Enable You To Save ££££'s by Doing Your Own Reinforced Concrete Base Construction for Garages and Sheds

The most important consideration when building
a garage or shed is the reinforced concrete base construction

All of our concrete sectional buildings require a concrete base as a foundation.

If you have an existing concrete base

• It may be possible to use your existing concrete base if you already have one or are replacing your old garage.

• Your base must be flat, square and level.

• Ideally it should be slightly higher than the surrounding area so water cannot settle at the bottom of the garage wall panels.

• If it is cracked it may be an indication that it has subsided or it has been undermined by vermin or was not very thick when first laid and should be viewed with some suspicion.

• If you are in doubt you will be well advised to seek the advise of a local ground-works expert, you will find these in your local directory or on Yell.com

The concrete base itself should be a minimum of 100mm (4”) in depth in the centre and 152mm (6”) in depth approximate. 300mm (1’) all around the perimeter where the weight of the garage walls will stand, and be 150mm (6”) longer and wider than the external size of the building, e.g. giving 76mm (3”) extra all around the building.

• Never even consider NOT having a concrete base or cutting corners.

• Concrete slabs, tarmac or block paving are not acceptable and will not carry the weight of a concrete garage.

• All suppliers refuse to build a concrete garage to a site where a concrete base has not been provided, some will just deliver as a D.I.Y. project, but this will invalidate the guarantee.

Please note: If your building has brick fronts then the overall length of the building will be between 2” and 4” longer.

So as to ensure that your base is square, measure out a 3-4-5 triangle (see diagram below) before securing the shuttering prior to concreting.

To check that the base is square, measure the diagonals of the base (see diagram below). Both corner to corner measurements should be the same.

What if my base is larger than the recommended size?

We would ask you to mark out the position on your concrete base so when the erectors arrive they will know your preferred position.

What is the best method of constructing my concrete base?

There are various methods that are acceptable:

The simplest is to shutter up the area where you are going to erect your garage with strong boards at least 4” thick, dig out a small trench about 1’ wide all around the sides and increase the depth of this trench to approximate. 6” deep from the top of the boards to give greater strength where the garage panels are going to stand.  Then insert a damp proof membrane, which can be purchased from most builder merchants, followed by ready mixed concrete with a fibre additive to reinforce the concrete, leveling this off to the top of the boards and making it smooth.
PLEASE NOTE: This type of base is only suitable where you soil type and site is stable and not liable to subside, if in doubt consult a local ground-works expert.

If your site conditions do not allow the above method. you should shutter the area as above, then dig out the soil to 4” deep (6” around the sides and ends) then lay a sub base of compacted hardcore to a depth of 4” in the centre, (6” around the sides and ends as above), then insert a damp proof membrane which is available from most local builders merchants.  Followed by ready mixed concrete with a fibre additive to reinforce the concrete, leveling this off to the top of the boards and making it smooth.  

If you are unsure how to do any of this you would be well advised to consult a reputable local builder or a ground-works expert.

Do I need planning permission for my base?

In most cases the answer is no, so long as it is more than 5m from the house or unless it is over 30square meters floor area, then you will need building regulations, then your local building inspector will need to inspect the site and agree the design and method of construction.
Regarding obtaining planning permission for a concrete sectional garage, please refer to our section on concrete garage planning permission by clicking on the 'Planning' link in the left menu bar.<

A solid concrete base is required to erect the shed on.

We will not carry out erection on paving slabs or tarmac.

A base minimum 3” (75mm) longer and 3” (75mm) wider than the external size of the shed is recommended. The concrete must be a minimum of 4” thick.

All of our sectional buildings require a concrete base as a foundation.
We can only offer a base laying service locally, or alternatively you can consult a local builder or groundwork's company. The base work will have to conform to the following guidelines.

The concrete base will ideally be slightly higher than the surrounding area so water does not drain from the ground to the base. The concrete itself should be a minimum of 4" (100mm) thick, and the base 6" (150mm) longer and 6" (150mm) wider than the external size of the garage with a water-poof membrane laid underneath the concrete (see above).

Example:
Garage: 16'1" x 8'3"

Base:

A 3 parts building sand : 1 part cement mix is recommended, with a PVA added to the mix.

IMPORTANT: Seal the garage on the inside only, not the outside of the panels.