You can request a limited replacement of unified materials, which are pieces that, when assembled, form a complete roof. While it is technically possible to replace only half of a roof, roofing experts don't recommend it. Some homeowners might consider it a cheaper option or think it saves time, but from the point of view of experts, replacing half of the roof often brings more harm (or expense) than good. To replace damaged shingles, you must remove the damaged shingle, install the new one, and seal the edges.
Because both sides of the roof have a different lifespan, you'll have to pay for repairs more often than for a complete roof replacement. But the reality is that there are good reasons why an accredited roofing contractor doesn't recommend replacing half of the roof. If the damage is widespread or if the roof is near the end of its useful life, you may need to replace everything. By replacing half of your roof, you don't get the warranty protection you expect after investing in a replacement.
If you have a leak or other minor damage, the good news is that you probably won't have to replace half of the roof and can get by with partial repairs. If there was a storm or periods of strong wind and you lost some shingles, it probably won't be necessary to repair or replace the roof on a large scale. If only parts of the roof are damaged, it's possible to replace only the affected area, but that may not be a good idea. In the end, if your roof just needs to replace a few shingles or do some minor patches, you can hire a roofer to do those small repairs for you.
If your roof is more than 20 years old and most of the shingles are damaged or heavily worn, it's time to replace it. Replacing only half of your roof may seem like an attractive option due to its cost-effectiveness and time-saving benefits. However, this approach can bring more harm than good in terms of warranty protection and long-term maintenance costs.