Although a wavy roof is unaesthetically pleasing, a common concern is if it affects the performance. It is agreed that a wavy roof takes away the appeal of a home, no matter the cost of materials that were used. Determining the underlying issues as to why your roof is wavy is the first step. There are a few possibilities for the reasonings behind a waved roof some more problematic than others. As always, contact a local roofing professional to determine a more thorough inspection of your roof to figure out the cause.

Installation
We can not say this enough “Not all work is created equal,” if you are looking for the cheapest roofing company, chances are you will get the cheapest work. Poor installation is a direct result of a wavy roof. It is urged to find the best roofing company in your area, who is trusted by customers who have left mostly positive reviews. Thankfully there are many platforms where a customer can leave a review for a company. Of course there will be a few disgruntled customers that no one can make happy, try and look at the overall rating of the company.
Materials
Depending on the type of roof you have, certain products or roofing materials are more prone to waving than others. For example asphalt shingles have the highest probability to wave and curl. Asphalt shingles are the lowest quality material and if not installed properly will cause your roof to resemble the ocean.
Foundation
Many people would not assume firstly that the issues they are having with their roof is because of their foundation because the roof is on top of their home, but this can be the case. The framing of your home has a huge impact on the way that your roof sits. The decking or “plywood,” is the foundation for your shingles, this can be an issue if it was not laid properly. Any issues with the decking on your home can result in a visible wave on the roof. Damaged decking can also be very dangerous, this could be an indication of water damage through shingles or issues with ventilation. If you think this might be the issue with your roof be sure to consult with a local roofing professional.

Underlayment
The roofs underlayment is a material that is placed between the roofs decking and the shingles. When asphalt shingles are being installed, felt paper is placed between them and the decking to act as a back up waterproof membrane. Felt is required as the first layer of roofing over the wood. If the felt paper is poorly placed beneath the shingles this will also result in a wavy roof. If the felt material was not fully dry pervious to installation or the day is extremely humid, chances are a slight wave can be seen. This type of roof wave is most commonly only seen after a new roof installation. Over time this issue is naturally corrected from the heat and is not a permanent issue.

Re-Roof
If you have a roofing company that suggests laying a new roof over your old one, we suggest you go with another company. This is a lazy way to install a new roof and will result in issues. If a new install is laid over an old roofing system, you will see an unnatural waviness that will never go away. Unfortunately your entire roof will need to be stripped down to the decking, if that is not damaged as well and reinstalled. Although you think you’ll be saving money by opting out of a the tear-off, it will likely cost you much more in the end if it was not done properly. Roofing warranties are another concern to think about, some warranties may not cover your roof if there is underlying damage unseen by the new roof laid over the top.
Shingle placement
The way shingles are laid out if they are not exceptionally precise, will result in a wavy roof. An inaccurate measurement or improperly sized shingle tab can be the culprit also. This is another reason that working with a trusted roofing company is essential. The lowest quote is usually not the best, you get what you pay for. If you want your roof done correctly, paying for experience is the key. Look for a roofing company that has been around for a decent amount of time, with reviews and pictures of their work to back up their claims on their website.

Sagging Roof
Roof lines should be as straight as an arrow, if you visibly see sagging, curling or dips then your roof has a problem. It is possible that it is caused by something basic that you could handle yourself, but it is more likely to require the intervention of a local roofing professional. As a homeowner you should become familiar with your home and roofs anatomy. If your home has an attic, climb up and take a look around, the horizontal boards under your feet are the roof joists or ceiling, the sloped board above your head are the rafters, this is all attached creating a triangle. This shape is meant to hold a large amount of weight, typically the weight of your roof and roofing materials.
A sagging roof can be the result of the ceiling rafters, the rafters are joined together in the center to create a longer span. With heavy snow, pressure is put on the roof and it can cause the rafters to push outward and turn. Together this causes sagging within your roof, even the slightest sag becomes noticeable from the outside. Problems should be evaluated by a local roofing professional so more damage is not done. The extent of the fix can be difficult to determine, unless you see visible broken rafters, beams, or joists.
