Determining whether the roof can hold the solar panels is very crucial before the installation. This is very simple. All you have to do is make sure the current weight capacity of the roof can withstand the extra weight of the solar panels and the mounting accessories after the installation.
As we stated before roof weight capacity has to be larger than the weight of the solar panels. By this article we like to cover;
Weight capacity of the roof
The weight capacity of the roof is the maximum weight that the roof can withstand. This includes the roof weight, weight of the workers, equipment, etc.
Roof weight is determined by the materials used to build the roof. This is called a dead load. Dead load is mostly constant over time. Then the weight of the workers or other equipment and objects is called a live load. This varies over time.
When planning the house, designers make sure that the roof can withstand both the live load and the dead load. Also, they consider the environmental load too.
Environmental load is the load due to the wind, rain, snow, etc.
How to determine the roof weight capacity?
Roof weight capacity is determined during the building stage of the house. As we mentioned earlier it depends on the dead load, live load, and environmental load.
When we build a house we have to follow a building code. Rules and regulations in this building code vary from state to state.
The minimum roof weight capacity requirement for a standard roof is about 20 lbs per square feet. But as we said before this value varies.
Factors that affect the roof weight capacity
The design of the roof hugely affects the weight capacity of your roof. This is a complex topic as there are many architectural aspects we have to talk about when it comes to the design of the roof. Such as slope of the roof, beam positioning, etc.
We can simply say that the standard roof has about 20 per square feet capacity and a flat roof has about 100 lbs per square feet capacity.
Even though roofs are designed to hold a specific load with aging this limit reduces. Most materials of the roof tend to decay and weak with time.
So the weight capacity reduces with time. So even though your roof is made from good quality material you have to consider the age of your roof.
Exposure to rain, sunlight, and snow can accelerate the aging process.
Good quality materials ensure that your roof lasts long and strong. Usually, the shingled roof has a weight capacity of about 20 lbs per square feet, and roofs built with very sturdy materials like concrete, clay has weight capacities of about 27 lbs per square feet.
Wood roofs and slate roofs are not suitable for solar panel installations. These materials are brittle. So the workers/ installers can not move on the roof easily. Also, these materials have less lifetime. Solar panels have around 25 years of lifetime. So installing solar panels on these roofs is not a good idea as the roof may not be able to withstand the weight of the solar panels for a long time.
Then you have to remove the solar panels and repair or replace the roof and reinstall them. this process costs you more money.
Also, a wood roof can present fire hazards so it is not recommended at all.
As stated earlier when designing a roof we have to consider environmental factors like wind, rain, snow level. humidity, etc. Especially snow will add extra load on the roof. So your roof should able to withstand all these external forces.
Also, these environmental factors accelerate the aging process of the roof.
So if you did not use suitable materials for the weather of your area your roof will be broken down pretty quickly.
Weight of the solar panels
The weight of the solar panels mainly depends on the number of modules they consist of and the mounting device.
Home/ residential solar panels mostly weigh about 40 lbs each. Add about 2.8 lbs per square feet. But this can be varied according to the manufacturer.
To find out the total weight of your solar panel array you have to multiply the weight of the one solar panel from the number of solar panels in the array.
Mostly the residential solar panels consist of 60 solar cells and solar cells used for commercial purposes contain about 72 solar cells or more.
Follow are the weights of 60 cells panels and 72 cells from well known manufacturers;
|Manufacturer||60 cells||72 cells|
|Sun power||33 lbs – 41 lbs||–|
|Vivint solar||42 lbs||>50 lbs|
|LG||38 lbs||44.75 lbs – 45 lbs|
|Solar world||40 lbs – 47 lbs||47.6 lbs|
|Hyundi||38 lbs – 41 lbs||50.5 lbs – 51.1 lbs|
|Canadian solar||40 lbs – 51 lbs||48.5 lbs – 49. lbs|
Can reckless installation affect the roof?
Yes, it can.
Correct installation of solar panels requires a lot of work. Most of the time solar panels should fix to the roof by drilling the roof. This has to be done by professionals for sure.
If not there can be small leakages that can go undetected for a long time until they ruin your roof completely. So having very competent installers for this work is very important.
When installing the panels, installers have to be up on the roof. They have to move around the roof. This also has to be done carefully. Otherwise, they can accidentally damage your roof and you have to spend more on the repairs.
Then lastly when placing the solar panels on the roof the weight has to be evenly distributed. If the weight is concentrated more on a part of the roof, the roof can damage.
So careful installation is very important to maintain the stability of your roof.
Why knowing whether your roof can hold the solar panel is important?
If your roof is not strong enough to hold your solar panels it will break down. It can be either small damage or the whole roof can fall apart.
This can result in lots of damages to your property. Also if there are people at that time they can get serious injuries.
So knowing whether a roof can hold these later installations like solar panels before installation is very important for the safety of both residents and the property.
Alternatives if your roof is not strong enough.
There are mainly two options;
- Replace or repair your roof.
- Use ground solar panels.
Sometimes repairing your roof can be enough to increase the strength of your roof. But if your roof is not made from the right materials or the damages are not easily repairable you have to replace your roof. But this can be very expensive.
The cheaper option is to use ground solar panels. But using ground solar can be less effective if we compared it with roof solar. But as we said earlier it is a lot cheaper than spend money on replacing your roof.
Common signs that show you that your roof is not safe to add extra load;
- Cracks on the roof or the ceiling.
- Cracking or squeaking sounds from the roof or the ceiling.
- Sagging roof.
If your roofs are not predesigned to install solar panels then you have to make sure that the current weight capacity of the roof is large enough to withstand the weight of the solar panels and the mounting accessories. Shingle roofs, clay roofs, metal roofs, and concrete roofs are highly recommended. But wood roofs and slate roofs are not recommended for many reasons. Even though you had designed your roof with a certain weight capacity this change over time due to many factors.