If you had new siding installed by another contractor, but find spots of damp on your inside walls, it is possible they did not waterproof the butt joints correctly. We discuss the correct way to do butt joint flashing, and answer some questions that may be bothering you.
Why Flashing Butt Joints is Critical
A ‘butt joint’ was originally the woodworking label for pressing two pieces of timber against each other, so they ‘abutted’. This is one of the simplest joints, and unavoidable in a long row of siding when using standard lengths:
- Plan your siding joints so you stagger them, and they are not obvious.
- Make sure your joints are over supporting studs, so they cannot ‘float’.
- Allow a 3/16”gap between abutting siding, to allow free-flowing expansion.
There are various ways of flashing butt joints to waterproof them. Some sources recommend filling the gaps with silicon seal. However, this can dry and crack in the sunshine, and inevitably fail.
That’s why we support James Hardie’s recommendation to seal the leak at the source, which is behind the siding strips themselves. The image at the top of this post, and the diagram below illustrate your main takeaway from reading this article, for which we thank you.
How to Flash Butt Joints Correctly
Butt joint flashing may be any durable material that is waterproof, and does not react with cement products. James Hardie recommends finished coil stock, code-compliant water-resistive barriers, or their own proprietary product.
They stipulate six-inch-wide flashing that overlaps the course below by one-inch. This should provide an effective, low cost solution that protects against moisture intrusion, while complying with local building codes.
More Useful Tips for Lapping Fiber-Cement Siding
- Remember to seal the abutting ends of the siding before attaching them to the studs.
- Cut suitable wooden wedges to temporarily space siding before attaching it in place.
- Take care to protect the house wrap behind the siding. Slip the flashing in carefully.
- You may find one or both pieces of siding deflecting out of line. Use suitable nails to correct this.
Could This Be a Job for the Experts?
Fitting new siding to a home is not a high-tech job, although there are many details to remember if you want a decent result. Valiant Exteriors offers a one-stop siding solution to homeowners in Calgary. Please give us a call on (403)829-1661, or write to [email protected] if you would like to explore our services.
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