Why re-stumping is important
House foundations repairs, such as re-stumping, are crucial to ensuring the safety and stability of buildings because, as with any physical support, foundations are bound to wear out. Adelle King reports.
Timber pile foundations, which were a popular option for housing foundations in the past, have seen a resurgence in recent years as consumers look for environmentally friendly building options that are aﬀordable as well as durable. Pile foundations are also popular thanks to their ability to be used on sloped areas or sites with poor soil quality, which is common in many areas of Australia.
Peter Llewellyn, who is a timber specialist and an expert with Forest and Wood Products Australia (FWPA), says there are also many beneﬁts to using timber stumps for building contractors.
“Timber stumps are readily available and easy to make connections to ﬂoor bearers. Adjusting the height of timber stumps is also simple and although dense hardwoods can be heavy, treated pine is light and durable, which makes it easy for builders to handle.”
However, unlike concrete or galvanised steel, timber is a natural material that will break down over time and timber stumps will therefore require restumping every 20-70 years depending on the timber used, soil conditions, drainage and termite attacks.
Many home owners don’t realise their houses need re-stumping and only ask for checks during renovations or if they’re selling the home but stumps should be checked regularly to ensure proper health.
“People are inclined to wait until something goes wrong on the principle that ‘if it ain’t broke, don’t ﬁ x it’. However, a look under the house to see what’s going on is important, particularly at the stump ground line and just below,” says Peter.
The strength of the building largely depends on the strength of the foundation so it’s important stumps are checked before signiﬁcant damage can be done to the house. If the deterioration of stumps becomes so bad that it aﬀects the foundations, then the house will become an unstable and unsafe structure for people to live in.
If a house was built before 1970 or has cracks on the internal and external walls, doors and windows jamming in their frames, sloping ﬂoors, decay of foundations beneath the house or damage to plumbing then it is likely it will require re-stumping.
“When it gets to this point, where walls are cracking and doors and windows are out of plumb, action is overdue but it can also be worth restumping if alternations and additions to the house are under way that will impose a greater load on the supporting structure,” says Peter.
The type of soil and where the customer lives will determine what type of stump material is used, with Victoria favouring rot-resistant timber stumps, such as Victorian red gum, and Queensland generally choosing copper chrome arsenate treated pine.
Since the process involves replacing a building’s foundation supports, re-stumping can be an extremely time consuming process. The area around the defective stump or stumps has to be jacked up, the stumps need to be supported oﬀ the ground while concrete pad footing is poured in and then the ﬂoor joists are lowered back onto the new stumps and secured in place.
Now though, a New Zealand invention is helping to increase eﬃciency and productivity on construction sites that require timber stumps for restumping or for house piles, deck piles and retaining piles.
Known as the Space-IT Pile Pad, this invention means builders do not have to worry about bracing or supporting piles oﬀ the ground, making installation quick and easy.
“I’ve been building for nearly 18 years and I was sick of suspending and bracing when I needed to get posts in the ground. I saw the need for a product that would make building foundations easier and faster, and the Space-IT Pile Pad was born,” says Space-IT inventor and managing director Jarrod White.
The Space-IT Pile Pad is a square timber pile locator and supporter that has been designed to provide temporary support for timber piles prior to concreting. It’s made from 100% recycled plastic and has been oﬃcially tested to 2,000kg of load on very solid ground. It features a 40mmdeep, square cup that sits on top of a 100mm-deep base, which is designed for locating the base of timber piles above the ground.
Builders simply dig or drill a hole to the speciﬁed depth and diameter, ensure the base of the hole is suitably level, screw the Space-IT Pile Pad on the bottom of the pile using four stainless steel screws and align the pile roughly to string lines. Once level, the pad is pinned to the ground via the holes on the base and supplied plastic pegs, before concrete is poured in. Concrete needs to be well vibrated into place and then it can be left to set.
If smaller posts are being used, such as 90x90mm, builders simply add a 15mm packer to each side that they will be screwing to.
The Space-IT Pile Pad can also be used with steel posts, as long as the base of the steel post is capped with a steel plate so that it can sit properly inside. The steel post is then attached with steel self-tapping screws through the side of the Space IT pile pad.
The Space-IT pile pad means there is no time wasted waiting for concrete to go oﬀ before bearers can go on.
“Space-IT Pile Pad cuts timing down on putting posts in the hole and getting them ready for concrete. Whereas setting up 30 piles used to take nearly a whole day, with the Space-IT Pile Pad 30 piles can be done in less than two hours,” says Jarrod.
The Space-IT Pile Pad also provides building contractors with the assurance of knowing that every stump is accurate and complies with Australian and New Zealand Standards regarding concrete pad footings.
“Space-IT Pile Pad gives you 100mm to cap oﬀ the bottom of the hole and seal oﬀ the post. It just makes building foundations easier. You don’t need to muck around with site concrete or supporting the pile oﬀ the ground,” says Jarrod.
For re-stumping, these time saving beneﬁts are extremely important for home owners as it can reduce the amount of time everyone living in the house is asked to move out for.
Unfortunately there is no way to prevent restumping for timber and even concrete and steel stumps are not guaranteed to prevent re-stumping as they are still susceptible to corrosion.
While choosing a suitable type of timber or preservative treated species, avoiding damp earth adjacent to the stumps and keeping frequently watered garden beds away from the house will signiﬁcantly increase the shelf life of timber pile foundations, restumping is unavoidable.
It is therefore important that stumps are being checked every few years regardless of the material used so that issues can be addressed before they become major problems.