Can I use underlay to build up my mat recess?

The pros and cons of building up your recess using underlay. Plus, 3 times you definitely shouldn’t.

We recently posted an answer to the question: how deep should a mat recess be? And if yours is too deep, you might be looking for a way to build it up and ensure your mat fits perfectly.

When first built, a typical mat recess is 40mm deep in terrazzo flooring, up to 80mm deep in concrete slabs and between 15mm and 20mm in tiles or timber floors. Most commercial entrance matting is between 9mm and 12mm, so almost all building managers and mat installers will come across this problem at some point in their careers.

A recess made too deep is easier to deal with than a recess made too shallow, so if this sounds like you, you’re in luck. You can build up your recess yourself. But there are a few caveats.

1. Traffic type

If your mat needs to support wheeled traffic, it should not be built up using underlay. Wheeled traffic includes carts, trolleys, scissor lifts, pallet jacks and even vehicles.

This is because the underlay and mat materials will have different properties, and the downward motion of heavy wheeled equipment will cause the underlay to move. Over time, the underlay will bunch up and create a trip hazard.

If your entranceway will see wheeled traffic, you need to level your mat recess professionally. For more information on the levelling process, check out this article on how we install entrance matting.

2. Traffic level

Just as wheeled traffic can prevent underlay from being an option, high levels of foot traffic do too.

We only recommend using underlay to build up your recess if you expect a low level of foot traffic to pass through your entranceway. For information on what we mean by each traffic level, check out this guide to what we mean by traffic levels.

If your building is a school, shopping centre or public building, do not use underlay instead of a correct floor leveller.

3. Building Code of Australia

The Building Code of Australia sets guidelines for mats to be as safe as possible. These include dimensions, safety certification and materials.

While the Building Code only applies to contractors or construction industry participants, most people that expect a high level of traffic should follow it too. Even if you don’t expect much footfall, you will benefit financially – and perhaps legally – from following the code.

We always encourage our customers to invest now, as it almost always saves you money in the long term. Skipping the proper recess levelling process is one of those times that the short-term savings are cancelled out later with expensive repairs.

So, when should (and when shouldn’t) you use underlay instead of a proper floor leveller?

The benefits of using underlay to build up a recess

If your entrance is not covered by any of the above caveats, using an underlay to build up your recess can save you time and money.

Underlay is significantly cheaper than self-levelling concrete, but that isn’t the only reason it’s the cheaper option. Anyone can install a mat onto an underlay. It takes training and experience, however, to install a mat correctly by levelling the floor.

Without the additional builder, your mat installation fee is reduced by the additional call-out fee, labour costs, and materials. A great quality underlay is also much softer than concrete, so it is a more forgiving material in terms of fitting into a certain-sized recess.

It sounds enticing, but we still don’t recommend it to most customers. Here’s why:

The disadvantages of using underlay to build up a recess

In the image below, you can see that the self-levelling compound has cracked and crumbled. Whoever laid this floor has cut corners by using an indoor floor levelling compound instead of a proper floor leveller. This will also happen if sand and cement are used.

Unfortunately, if the traffic levels are too high or moisture finds its way to the recess (which it will), this is what will happen, and you will be up for an entire rework.

With underlay, cracking is not the issue but bunching and moving. This is even more of a safety hazard, as the bunched material creates a trip hazard. Any money saved early on might be lost in a slip, trip and fall lawsuit, so we do not advise it in most situations.

Can’t decide? Let us help.

If you still aren’t sure whether underlay is the best option for you, our team of friendly matxperts are happy to help. For personalised recommendations and advice, or answers to any of your questions, feel free to reach out on 1300 628 746 or [email protected].

You can also reach us using the chat function below.

For more information on entrance matting, check out the FAQs section at the bottom of the entrance mats page.