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.
For extra credits, have a read of this technical report:
https://fwpa.com.au/wp-content/uploads/2009/04/PNB036-0607_0.pdf
Matt Cornell
Cornell Engineers