Concrete Shed Slab FAQ with Ross

28 January

We recently published a handy glossary of terms about concrete. Now that we know the lingo, what do we need to know about cement before building a farm shed? In this article, we chat with Buffalo Built Managing Director Ross Barker about the importance of getting the concrete base for your shed right and a few things to consider in the process.

Picture of Ross Barker
Ross Barker

Managing Director, Buffalo Built

In this Article:

The Cement Slab for Your Shed Floor: Does a Shed Need to be on Concrete?

Firstly, Ross highly recommends that all farm sheds have cement floors, and the most economical time to pour the slab is at the beginning of the project.

“More than 90 per cent of the residential and farm sheds we build have cement floors,” he says.

“It’s more economical to cement your shed at the start of your build, but if your budget is tight you can always add it in later.”

“The only time it’s not critical to have a slab is for open-fronted hay and machinery type farm sheds, where crushed rock is fine. But in a shed where you have valuable items behind closed doors, you want to seal it off from dust and vermin, and a concrete floor presents a great way to do that.”

Concrete flooring is also important where your shed has roller doors because they have rubber seals on the base of them. Having a concrete base helps improve the longevity of this crucial part of the roller door. Ross explains that a flat concrete slab helps to create a good seal, keeping dust and debris out.

“It’s best if you can have the door come down on a cement slab. It certainly helps keep down the dust. Having a slab also allows for a rebate at the roller door entrance, so water can run out of your shed, not into it,” adds Ross.

There is a whole range of benefits to having concrete under your shed – here are some of the most common questions we get asked about slabs.

farm sheds

How Thick? Shed Slab Requirements

Ross notes that the recommended minimum thickness is 100mm, although for commercial and industrial sheds, Buffalo Built has options of 125mm and 150 mm thickness to support heavy machinery and equipment. Understanding how your shed will be used is part of the design process, and that will help us recommend the right slab thickness for your project.

Can I Build the Concrete Floor Slab Myself?

Everyone loves DIY, and we know if our clients put their minds to a task, there’s a fair chance they can do it. However, in this case, it’s wise to leave concreting to the professionals.

“We recommend you use a trusted and experienced professional for concreting for your shed. “If the slab is 50mm out of square, the shed will be out of square as well,” explains Ross.

“It’s very expensive to repair the slab if it’s not done right.”

He also advises that a professional concreter will be able to choose the right size of reo and make sure you have the correct MPa (strength) of concrete. At Buffalo Built we typically recommend a minimum of 25MPa in slabs.

Can I Build a Farm Shed on an Existing Concrete Floor?

“We don’t recommend building on existing slabs,” Ross says. “But it can be done.”

Keep in mind that sections of the slab will have to be cut out for the footings of the shed, which can be difficult. Also if the slab is larger than the footprint of the shed, the iron sits on the concrete, which can cause a whole host of problems.

Conversely, if the slab is smaller than the shed, you end up with awkward spaces that aren’t cemented which can affect how you use the shed space.

“Ideally, a new slab should be made specifically to suit a new shed design,” adds Ross.

“We recommend you use a trusted and experienced professional for concreting for your shed. If the slab is 50mm out of square, the shed will be out of square as well."
Ross Barker
Ross Barker

What Are Expansion Joints And Why Are They Important?

Expansion joints help compensate for expansion and shrinkage in concrete due to temperature changes and other factors. When concrete first hardens and sets, it reduces in volume, which causes some degree of shrinkage. If the concrete is poured without allowing for this shrinkage effect, it can crack as it hardens.

Expansion joints usually take the form of either saw cut joints, which are 15-20mm cuts with a saw into the slab, or trowel joints (obviously created with a trowel).

On the topic of cracks – in hot weather, additives can be put in the concrete to slow the curing process, which can help prevent cracking caused by rapid hardening. If you’re building in the middle of summer this might be a factor to consider.

How Do I Run Electricity and Water to My Shed?

Think about what you will be using your shed for before you pour your cement slab. Ross notes that power can usually be added retrospectively because cladding can run conduit easily. However, if you need plumbing, then conduit needs to be included in the slab before being poured.

“A lot of people like to have conduit in the slab,” he says.

“This needs to be sorted out from the beginning as it cannot be fitted later.”

Your Concrete Shed Slab: Do it Once, Do it Right

There’s lots more to learn about concrete slabs, including using the correct base and waterproofing protection under the concrete. Most importantly, Ross says it’s important to discuss your slab needs with experienced professionals – both the shed designer and the concreter who does the installation.

“A lot of people like to have conduit in the slab - this needs to be sorted out from the beginning as it cannot be fitted later.”
Ross Barker
Ross Barker
Picture of Ross Barker

Ross Barker

Managing Director, Buffalo Built

Contact Buffalo Built Sheds Wangaratta and Mansfield

It’s worth doing right the first time, so make sure you’re dealing with an experienced team that can help you get the best result for your shed. At Buffalo Built, we have more than 100 years of combined experience in the design and construction of steel structures, and our sheds are backed by a lifetime guarantee.