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By Cara Mackay on 23 May 2019

What kind of base do you need for a Garage?

Garages don’t have floors, so they need a concrete plinth to sit on. This is where most people who are thinking about buying a Garage start to ponder.

“Okay so I want a Garage, but I need to have a base first…”

Oh, Shedlord – what now?!

Well, the plinth needs to be strong enough to carry the weight of the walls and the roof, as well as whatever you’d like to put in it.

It also needs to be a certain size, made from the right stuff, be in square and BANG ON level.

Not asking for much right?

Way back, in the beginning, Garage bases were always a nightmare to organise. So bad in fact, we had to start making them ourselves.

Ludicrous! A joiner making a Garage base? Yep. It happened.

Please note: We highly advise you obtain landscaper/construction quotes for base work before ordering your Gillies and Mackay building to obtain a full and clear picture of project costs.

Three things we know about Garage bases

1. Excavation

If your existing site is MENTAL unlevel, you have horrendous access and a terrain soft as butter, then it’s going to take a lot of preparation before we get anywhere near the concrete.

If your Garage is where ‘normal’ people have their garages, to one side of the house, already level AND in good standing firm ground, then you can put the kids’ university funds away! We’re going to have an easier ride here.



2. Sub Base

Once the area has been excavated we’ve got some serious jobs on.

Depending on the ground condition you can expect to lay a minimum depth of 100mm of T1 hardcore. Once this is compact and level you would lay a DPC (damp proof membrane) before the concrete gets poured.

G&M Garage Base Specification

3. Concrete

I like to call this the list of three to concrete perfection:

  • To Size
  • In Square
  • Level

Not all base layers appreciate our method. Some like to make the base bigger than the Garage.


Don’t do that.

To Size

Before concrete is poured there’s a timber frame built to shutter the concrete in – this is where the measurements are so CRUCIAL!! Setting up the formwork takes precision and close attention to where you’re measuring from.

If your base is not to size then we cannot slot the walls over the sides allowing the water to drain away from the building properly.

In Square

Keeping your base ‘in square’ keeps the building in square. How you do this is by using the corner to corner measurements.

Finally… a use for all that geometry you learnt at school! The square is imperative to how the building goes together. If your base is not square, Calum will have to ‘THROW’ the panels which isn’t nice to see, nor is it a pretty finish.


Some base layers cannot fathom the prospect of not having a ‘run’ on the level. A run on a base is typical to allow water to run away. Our Garages do not want a run because they don’t leak so there’s no water. This is common on hard landscaping but is definitely not welcome on a garage base.

LOOK?! Isn’t she beautiful?

Stunnin’ Concrete Base

Now I know what you’re thinking… I cannae do that?!

You’re right, so please, for all the Shed love in the world, do not try it – unless, of course, laying concrete is your actual job.

Who do G&M recommend for your Garage Base?

At G&M we only work with amazingly handsome and clever trades. Thankfully we know just the team to kit you out with a magnificent Garage base.

We recommend Carmichael and Baxter for all our concrete bases. We love C and B because they know what we’re talking about. They are kind and thoughtful when dealing with our customers, and they get the job done when they say they will, with the utmost precision.

Paul, Carmichael and Baxter’s Estimator, was kind enough to help me understand their process and pricing.


The following costs are budgetary meantime, exclude VAT and, are based on working in the Fife area in 2019.

6.00m x 3.00m x 0.150m deep concrete base  –  £3,100.00
6.00m x 6.00m x 0.150m deep concrete base  –  £3,800.00

Excavated spoil remains on Site.

Some of the factors affecting the above rates which would be an additional cost are as follows –

  • Access to the work area, if this is awkward with maybe poor access for Plant.
  • Excavated spoil removed from site, if this is required, can easily add £600 to £800.00 to the above rates.
  • If the existing Site is not level, additional hardcore may be required which would be extra.
  • If the Site is more than an hour from Cupar, there will be travelling costs to add, if more than 3 hours then overnight accommodation will be required.
  • Ducts for services would be a small additional cost.

We would prefer to survey the Site prior to pricing to make sure all the above are included from the start.

We can – and do – pour bases all over the country, but the further away we get from home with travelling & accommodation to factor in makes it harder to be competitive with more locally based Contractors.


So, there you have it Sheddies! A Garage is only as good as the base it stands on – so be sure to get it right.

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