DIY Home Maintenance Part 4: Underfloor

A real hobit house

Depending on your situation, the sub-floor area of your house needs careful maintenance, just like any other part.

If your house is constructed entirely on a concrete slab, investigating the sub-floor could be tricky. But many houses in NZ are built with a combination of slab-on-ground and pile construction. These often include retaining walls.

Just as a good roof is important for a weather-tight home, your foundations are clearly holding everything up. Pretty important – but easy to forget.

Underfloor zones can present their own unique access challenges. This is particularly so of some older homes. You may have to pull out the overalls and be prepared to squeeze into some tight spaces. As always, assess the risks and prepare adequately.

Got your torch? Here are a list of things to look out for under your house.

Sub-Floor Moisture Problems

One of the main issues with the space under a home is moisture. There are a range of measures covered in the building code aimed at keeping this space dry and well ventilated.

But if your home is older or conditions have changed, you may have a moisture problem. Excessive moisture in the underfloor area can create a cold, damp house. Moisture can make it’s way up piles and other structures into the floor and framing, opening up the structure to mould, fungi and rot.

As we said at the beginning of this series, a dry home is a healthy home.

Is the soil damp? Are any sub-floor surfaces damp?

This is one of the first things to look for. If there does seem to be excess moisture, where is it coming from? Possible causes include:

Leaking or disconnected pipes – check all the waste pipes as well as water supply pipes.
Blocked drains – these could be gully traps on the outside of the house.
Leaking showers, baths or washing machines.
Surface water making it’s way under the house – changes in landscaping, the garden or neighbouring property can cause unexpected changes in water flow.
Springs – strange as it may seem, these occasionally appear some time after a house has been completed.

The first thing to check is that there is adequate sub-floor ventilation. Vents may not exist or may have become blocked. Depending on what you find, some drainage around the outside of the house may be required.

Once any issues have been dealt with, laying polythene on top of the ground under your house can markedly reduce moisture levels in the air space, which also helps to reduce heat loss through your floor.

General Wear and Tear

Whether there have been moisture issues or not, there is likely to be general degradation of the sub-floor structure over time. Keeping on top of this will save costly repairs down the track.

Some general items to keep an eye on are:

The condition of structural timber – is anything sagging or rotting?
The condition of metal fittings – bolts, nail plates etc. can be susceptible to corrosion.
The soundness of brackets supporting pipes.

General Movement

The ground is moving beneath you. If your house is on a sloping section, it’s likely that it’s slowing creeping down the hill. Usually, this process is very gradual, but under certain conditions (like earthquakes) this movement can be accelerated and the effects noticeable.

Signs that this is becoming a problem include:

Gaps between structural members like piles and bearers.
Cracks in masonry or concrete foundation walls.
Obvious signs of stress in sub-floor structural members.

Remedial action can usually be taken in serious cases of movement. The sooner you act, the better.

Who would have thought so much drama could be happening under your floor? Well, hopefully it hasn’t been – but there’s only one way to find out!

We hope these pointers will be helpful to you as you tackle this important aspect of home maintenance. Remember, if you need a seasoned eye on any problems, don’t hesitate to get in touch.

Keep Calm and Maintain your Home poster