February 02, 2023


If your home has been affected by recent floods and extreme weather and it has a crawl space or under floor it is essential that it is kept as clean and dry as possible. A healthy subfloor equates to a healthy home. If your subfloor is damp and dirty, this can lead to poorer health for the people living in the home. So, it is essential that in a flood situation, you don’t forget to check if your home has suffered from underfloor flooding.

If flood waters have come inside your home, then it’s more than likely the insulation under your floor will be wet and damaged. If the flood waters entered your underfloor, but didn’t make it into your home, there’s a chance the insulation hasn’t been affected, but you still need to check it to assess for damage.

If the underfloor of your home has been flooded, there are a few things to consider before you begin the cleanup.

Is your Underfloor Insulation Wet?

If your underfloor insulation has become wet, then it must be removed to allow the underside of your joists and floorboards to dry. If left in place, underfloor insulation can take weeks to dry, and even then, its performance will be compromised. Wet insulation left in place will dramatically increase the chance of mould growing either on the inside of your home or on the underside of the floorboards. It will also slow the drying process of the inside of your house.

Secondary damage of floorboards and joists are also a possibility if you don’t get your subfloor dried as soon as possible.

Can you access your Underfloor?

Before you start assessing the state of your underfloor, you need to check if the subfloor is accessible? Many homes don’t have a manhole that allows you to access your underfloor to carry out repairs or maintenance. If this is the case with your property, we recommend you get one created as soon as possible to allow inspection of the underfloor.

Before entering a Flooded Home

Check that there is no immediate danger from:

  • Continued flooding risk
  • Damaged structure
  • Electric shock – supply should be discontinued until initial checks have been carried out and the supply and installations are confirmed as safe
  • Leaking gas – supply should be discontinued until checked and tagged as safe
  • Overflowing drains or sewage systems.

How to Check your Underfloor

Once you are able to access the underfloor of your house and you’ve turned off the power, equip yourself with some PPE gear. Overalls, gloves, goggles, a mask and flashlight are essential items when you enter an underfloor, especially one that has been flooded.

After a flood, it is common for an underfloor to contain nails, glass, and other sharp objects, as well as mouse and rat droppings.

You need to also consider the chance of sewage and harmful bacteria having been carried into your underfloor. So, you definitely want to be prepared with the right equipment. Remember that an underfloor is considered a confined space, so make sure you have someone close by keeping an eye on you. It also goes without saying that you shouldn’t enter an underfloor if it is still flooded, or if heavy rain is forecast.

Make sure you turn your power off

As mentioned earlier, make sure you turn the power off to your home before you enter the underfloor. The risk of getting electrocuted is very real in an underfloor. Also remember that even if you do turn off the power, the main cable running from the road to your home will still be live. Make sure that you tape the switchboard in your home with a note, so that someone doesn’t turn the power back on while you are under there.

Once you’re under the floor check for…

  • Once you are under the floor, check to see if any debris has washed into the underfloor, is there rubbish, vegetation or silt?
  • Are there old storage items that have shifted in the flood?

All of this rubbish needs to come out to help increase the airflow under the house, which will help with the drying process.

Check the insulation for dampness, it should be dry to touch. If the insulation is wet, then it needs to come out ASAP to aid the drying process. Underfloor insulation is usually stapled to the joists under your floor either directly through the insulation (in the case of polyester insulation) or through blue strapping which holds it in place (in the case of fibreglass insulation). Polystyrene insulation is normally pinned into place.

Simply rip, cut or pull the insulation out and leave it on the ground. Move through the underfloor from the furthest point from the manhole towards the manhole. As you pull out several sections of the underfloor, you can then pull it along the ground and out through the manhole.

Please keep in mind that working in the underfloor is hard physical work and not for the faint hearted. Please do not attempt this work unless you are physically fit, have the right PPE gear and have turned the power off.

We are a professional insulation company with years of experience so have a chat to the G-Force customer service team if you are not sufficiently equipped or experienced in doing this type of work. Call 0508 088 888 or email

Check your Ground Moisture Barrier

If you have a ground moisture barrier installed, what condition is it in? Does it have tears or rips, has it come away from the ground. Is it covered in silt?

If the ground moisture barrier has been damaged or compromised by silt and debris, we recommend removing the damaged areas with the view to replace it with a new barrier.

Key thing’s to remember is that you want to:

  • Ventilate your underfloor as much as possible to help it dry as fast as possible.
  • Remove all rubbish, debris, wet insulation as quickly as possible.
  • If you can, take the baseboards off the subfloor to increase ventilation, if you can’t remove baseboards, ensure that the subfloor vents are clear of vegetation and other obstructions.




At G-Force Healthy Home Solutions we’re all about making homes warmer, drier and more energy efficient for Kiwi families.

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