Short Answer
Sometimes. The existing assembly must be evaluated for condition, flatness, moisture, rot, attachment, code requirements, and manufacturer installation requirements.
Detailed Explanation
Installing new siding over existing siding can save on labor and disposal costs, but it's not always appropriate. The existing siding must be flat and securely attached — any irregularities will telegraph through the new siding. There can't be rot, moisture damage, or structural problems beneath the old siding, because these will continue to worsen under the new installation. The combined thickness of old and new siding may create issues with window and door trim, electrical boxes, and other penetrations. Manufacturer installation instructions for the new siding may specify whether installation over existing siding is permitted. And local building codes may restrict the number of siding layers. A thorough evaluation of the existing assembly is necessary before deciding.
Why It Matters
Installing new siding over damaged or deteriorated existing siding hides problems that will continue to worsen and may cause the new siding to fail prematurely.
Common Mistakes
- ✕Installing over rotted or moisture-damaged siding
- ✕Not checking for structural problems beneath existing siding
- ✕Ignoring manufacturer requirements for substrate condition
When Repair Makes Sense
Localized damage to existing siding can be repaired before new siding is installed over it.
When Replacement Makes Sense
Existing siding has widespread damage, rot, or moisture problems that would compromise the new installation.
Questions to Ask Your Contractor
- ?Is my existing siding suitable for installation over?
- ?Are there any signs of rot or moisture damage beneath?
- ?Does the manufacturer allow installation over existing siding?
- ?Will the added thickness cause issues with windows, doors, or trim?