Nail plate back out. This is what it looks like. This is a photo of an older truss. When the truss was installed this steel nail plate was tight in the timber. There was no gap. The teeth of the nailplate were firmly embedded in the timber. Over time, with changes in the amount of moisture in this roof, the timber pushed and pulled and the steel teeth of the nail plate worked their way out of the timber. This nailplate is critical in transferring loads and keeping the truss strong. If the teeth aren’t embedded in the timber, the truss is at risk of sagging or worse still pulling apart under wind load. If your older roof trusses look like they have sagged, this is just one thing we look for. The solution? The teeth need to be re-engaged in the timber, the loads need to transfer between the pieces of timber again and something needs to be done to ensure the nail plate doesn’t come loose again. Send a builder or building and pest inspector into your roof to start with.
If you need advice on how to repair this problem, we’re just a phone call away.
Sometimes we recommend replacing the truss. Sometimes we recommend sistering a truss next to the degraded truss. Sometimes, we have bene able to repair the truss in place. It all depends on how many trusses are suffering or are likely to suffer.
If you’re building a sleeper retaining wall, you’ve probably been told you need an ag pipe and drainage system behind it.
But here’s the truth: sleeper walls are already free-draining—water comes straight through the gaps between the sleepers!
So, do you really need all that extra drainage work? Let’s break it down.
How Water Moves Through a Sleeper Retaining Wall
Sleeper retaining walls are not waterproof. They’re built with gaps between the sleepers, so water flows through naturally.
When it rains, water seeps through the wall and drains away without needing pipes or fancy systems.
Unlike solid concrete or block walls, sleeper walls don’t trap water behind them, so hydrostatic pressure (the force of water pushing on the wall) isn’t a big issue.
The Real Job of Gravel Backfill
Gravel backfill is crucial—but not for directing water into pipes. Its real purpose? ✅ Stops soil from washing through the wall gaps ✅ Lets water drain freely behind the wall ✅ Reduces pressure on the sleepers and posts
Without gravel, water can pool behind the wall, making the soil heavy and unstable. That’s when walls start leaning or failing.
Why Ag Pipes and Drainage Systems Don’t Work Here
Ag pipes rarely drain properly. If they sit too high, water just bypasses them. If they sit too low, they clog with silt.
Connecting to site stormwater is nearly impossible. Unless you have a proper outlet at the right level, pipes just fill with mud and stop working.
Gravity does the job for you. Water follows the easiest path—straight through the sleepers and into the ground below.
Need a Watertight Wall? A Sleeper Retaining Wall Isn’t the Right Choice.
If you need a wall that doesn’t leak (for example, to keep water out of a basement or protect a neighbouring property), a sleeper retaining wall isn’t the solution.
For a watertight retaining wall, consider: ✔ Reinforced concrete walls with a waterproof membrane and proper drainage behind ✔ Concrete block walls with a sealed render finish and a properly designed subsoil drainage system
Each of these options requires specific waterproofing solutions to ensure water doesn’t get through and build up behind the wall, causing pressure and failure.
The Bottom Line
Sleeper retaining walls are naturally free-draining. Gravel backfill is a must, but ag pipes and complicated drainage systems won’t fix poor design or bad site conditions. If you need a fully sealed, waterproof wall, sleepers aren’t the right choice—consider concrete or concrete masonry retaining walls instead.
Building a retaining wall? Want it to last? Get in touch with Cornell Engineers—we know what works and what’s just a waste of time.
Don’t rely on an engineer’s inspection certificate / Form 12 for structural work unless the person who inspected the work was:
a) an engineer
b) attended the site in person
c) took photos to show they were there
d) can provide those photos upon request
Too many times in recent months we’ve identified poor construction practices as identified by a HOMEOWNER even after the “INSPECTOR” approved the construction. The biggest joke in the industry is waiting to meet the inspector on site and when you call them they say they already inspected the work and it passed!!!
Where in the world are we that homeowners are being asked to know more than an engineers’ inspector who inspects 10 to 20 properties per day?
OH, WAIT! Perhaps that’s the problem!!! Nobody can inspect that many properties in a day when considering travel time, reporting time, and meeting with a builder to ensure they understand the defects/requirements.
Whether the industry is booming or dwindling, people (e.g., builders and engineers) are always looking for shortcuts—trying to find cheaper ways to get the job done.
But are they cheaper when homeowners then have to shoulder the burden of identifying structural deficiencies/problems and getting them fixed?
What of the builder who rightly claims the Form 12 is signed by an engineer so the work MUST be compliant?
Where does that leave the builder?
Where does that leave the homeowner?
Where does that leave the certifier?
Can they rely on the Form 12 and pass the responsibility to the engineer who signed the Form 12?
Go back and read our post on the Dog Ate My Homework. That’s the engineer’s get out of jail free. The paperwork doesn’t exist so the engineer can’t possibly be at fault. Right?
So now we have this endless loop of blame game shifters who have all managed to get away with doing a lacklustre job, backed up by incompetence, missing paperwork, cost-cutting and booming profits for work not even done let alone done well.
Does any of this sound possible in a modern economy? Look next door at the house being renovated! Look over the road at the house being built by that builder with the shiny marketing and promises of 6 month construction period!
Check out your local mass construction builder relaxing in his brand-new office, driving his shiny new luxury car and waving a middle finger at consumers.
Yep. Possible maybe even probable.
And this is in a state where we have a consumer watchdog, builder registration process, several builder’s associations (for protection of the builders against the pesky registration process), registration for engineers (including a stinky, decaying complaints process managed by bureaucrats) and consumers who are already fighting tooth and nail to keep some of their weekly salary for their dream home.
Builders are still struggling to understand the rules for head flashings over exposed windows.
And it will be their downfall.
Because these little timber trims, no matter how well they are painted, leak eventually and rot out and then allow water to rot your frame.
Sadly, sometimes the damage isn’t found until the QBCC warranty expires and then it becomes a homeowner cost.
So have a look at the tops of your windows. If they are exposed (there are specific rules) to the rain and sun and they look a bit like photo 1, chances are you might need our help with solving rotten framing at some point in the future.
This is the type of prehistoric joist-to-bearer connection that can lead to sudden and unexpected floor collapse if not rectified immediately.
The joist can pull out of the bearer slowly over the years and if not repaired NOW the depth the joist is secured into the bearer can diminish with catastrophic consequences. The connection can unzip leading to total and sudden collapse of the floor system.
“The general public and the building industry need to be aware of this particular method of construction in older properties, particularly the potential for joists to become disengaged from bearers and collapse in the same manner that occurred in this instance as a result of little or no bearing of the joists into the bearers.”
Builders, building inspectors, engineers and architects should ALWAYS be on the lookout for this type of detail and should always flag it to homeowners as needing repair under their duty of care.
More from the coronial enquiry:
“Mr Duignan said if a joist was pulling right out he would have expected to have seen it. The evidence of all witnesses asked was that in this case to tell how far a joist was engaged in the bearer would have involved pulling up part of the flooring deck which would have been relatively invasive and expensive.”
“The evidence of all witnesses asked was that extra securing for the joists in bearers could have involved a number of processes although the evidence is that most of those would be relatively inexpensive.”
“I formed the impression that Mr Duignan was a competent professional builder experienced in renovating old Queenslanders. He would expect to come across problems from time to time given the vintage of the construction.”
I accept that if he had found a problem that required attention he would have fixed it or brought it to the attention of the owners. If he had seen or witnessed a problem with the balcony support he would have sought to do something about it. I accept he had not.”
