Metal roofing attracts attention with its light weight and relatively low cost. The main advantages of the material include lightweight installation, which increases the speed of roofing work, and you can do such work yourself. The material is airtight and fire resistant. Tightness justified minimum quantity mounting holes or no holes at all.
Types of metal coatings
People have been using metal as a roofing material for a long time, and over the centuries of its use, many technological options have been invented. Instead of simple aluminum, sheet iron and copper, they now use original “constructors” with a set of fasteners, elements and additional parts for connecting connections. Such kits greatly simplify construction work.
The classification of roofing iron divided the metal options for the roof into the following groups:
Technological and easy-to-use roofing sets made from corrugated sheets and metal tiles are distinguished by a high price. For the same reason, many do not consider non-ferrous metals. If you choose the most economical device metal roofing with your own sheets, it is better to focus on budget materials. This will require steel sheets with a width of 1.25 meters and a length of 2.5 meters.
It is best to purchase steel with double-sided galvanization. It will cost more than its “black” counterpart, which is not coated with zinc, but the investment will pay for itself in the form of optimized wear resistance coupled with rare maintenance. At the manufacturer's factory, the cold-rolled material is completely immersed in a container with molten zinc, after which a dense protective layer appears on the surface of the sheets.
SNiP dictates the thickness of the material. According to the requirements of the standards, metal roofing (II-26−76) is constructed from thin sheet metal from the rolling industry. For a metal roof, steel with a thickness of 0.5-1.5 mm is suitable. It is easier to install thin sheets, as they bend to form the desired connections. But if it is planned to make drainage elements and additional parts from the same material, then it’s better to stay at a thickness of 0.6−0.8 mm.
Construction rules do not prohibit distorting the shape of galvanized plates, but this is still not recommended, since the integrity of the zinc coating will be compromised. Metal tools should not be placed on a galvanized surface during work; this requires a wooden lining. If the zinc protection is damaged, the performance will deteriorate.
Self-installation
The most economical and common type of laying sheets on the roof can be called seam technology. The basis of this principle consists of the method of connecting elements with curved edges, which form transverse and longitudinal seams (they are called folds).
Transverse seam joints are convenient when the horizontal size of the slope exceeds the classic length of the steel sheet. They come in double and single types and are called horizontal because they have the same direction. They are also recumbent - they are bent to the sides of the water flow so that there are no unnecessary barriers to the flow of precipitation.
Longitudinal seam seams should connect the covering elements along the vertical slope (side line of the sheet). They should not be bent so as not to cause stagnation of water on the roof. That's why they were called standing ones. Installation using seam technology involves the use of horizontal standing joints.
If possible, it is worth eliminating single horizontal connections, which can reduce the roof’s ability to resist atmospheric damage. Standing double seams are the most practical and reliable option. The seams are formed using a wooden screw and hammer or special electromechanical machines.
The main element of the roof is a part assembled from two steel strips with curved edges, which are required for further connection. This piece is called “paintings” and is assembled on the ground. You will need a special workbench that matches the length of the parts of the picture to be joined.
To splice paintings, homemade clamps are required: they are cut from the same sheet of steel, the strips have sides of 3 and 15 centimeters. They are attached every half meter from the vertical seam line. The required amount of fasteners is made in advance from scrap metal sheets. The parts are cut with scissors, since the grinder will leave uneven jagged edges and will also burn out the protective coating.
The assembled paintings with the edges prepared for joining remain to be lifted up.
The construction of a rafter system will differ little from the technology for constructing frames for other roofs. It is not necessary to place the rafters very often here, since the material is distinguished by its lightness. But the sheathing beam will need to be installed at intervals of twenty centimeters, because you need to take into account the ability of the metal to bend. Due to this, damage to the coating can be prevented.
The minimum slope of the slopes for a metal roof is 14 degrees, the maximum is 30. If the roof is insulated, then you will need to build a counter-lattice of thin slats on top of the waterproofing in order to form a ventilation gap between the insulating layer or the metal coating. Thanks to such ventilation, there will be an equal temperature on both sides, therefore, condensation will not settle, which can destroy the metal.
The eaves overhang is made of three or four solid boards. The ridge is formed by laying boards on both sides, they converge at a single point.
Assembly of elements and final installation
The assembly of a metal roof fencing must begin with the installation of crutches, which are installed every seventy centimeters along the eaves overhang. First, two crutches are nailed along the edges, a cord is pulled between them for subsequent alignment of other parts.
The paintings are transported by a car lift to a storage area organized above. Along the line of the second picture, clamps are attached every half meter; self-tapping screws are used for this. The clamp is positioned so that the picture laid on top can cover the point of its fixation. After this, the first picture is installed, its side line should coincide with the line of the pediment. The first element is fastened through with self-tapping screws.
Elements of a seam roof must be mounted according to a similar scheme: clamps are installed, then the installation of the next strip, connection with the previous sheet. The fold must be folded together with the fastening strips. Experienced roofers recommend strengthening seams with silicone sealant. And in order to avoid unbending homemade clamps, it is allowed to supplement their location with a riveting point.
And the final installation steps metal roof will look like this:
Additional lightning protection
There is an opinion that the metal roof itself acts as a good lightning rod, and therefore does not require additional protection. But a direct lightning strike can cause a fire, as the metal installed on the wooden sheathing will overheat. If the seams between the coating elements are reliable, then lightning protection will be carried out by connecting it through a down conductor.
The construction of a metal roof can rightfully be called the most economical and in a simple way arrangement country house. If you remember the technological rules when performing work and act carefully, then the erected structure will last for ten years without requiring repairs or any alterations from its owner. You just need to remember the installation rules according to building regulations and take into account the features of the metal coating.
When talking about roof coverings, most professionals and home owners will agree that one of the most practical solutions is a metal roof. Metal coatings are used to cover the roofs of individual cottages and multi-storey buildings, industrial enterprises and shopping complexes. What are the advantages of such coatings and what are their types, we will consider in this article.
When choosing a reliable covering for the roof of a house, many homeowners prefer metal materials. Such coatings protect the house well from water leaks, wind and other weather conditions. They are very durable, resistant to mechanical, temperature and chemical influences.
In private construction, metal roofing is often used also because the technology for laying it is quite simple. That is, even if a home craftsman does not have much construction experience, it is quite possible to assemble a metal roof with your own hands.
Types of Metal Roofing Used
The following types of metal roofing are used today:
- Flat coverings. In this case, the installation of a metal roof is carried out using sheet and rolled steel using seam technology.
- Profiled coatings. To install such roofs, profiled sheets of metal are used, this can be corrugated sheets or metal tiles.
- A special group of coatings consists of roofs made of non-ferrous metals.
Materials used for installing metal roofing
Let's consider the most popular materials that are used to create metal roofs.
Galvanized steel
This roofing option has been used for many years and remains quite popular, despite the emergence of more modern analogues of metal roofing.
Consumers are attracted by the affordable price, as well as the fact that the material is quite simple to work with, it is easy to cut using a special tool, and bends well. Thanks to this quality, galvanized smooth steel sheets can be used to cover any roof configuration.
Advice! When using galvanized roofing steel to cover the roof, there is no need to separately purchase additional elements. The strips for the cornices, gutters and ridge can be cut from the base material.
Galvanized steel compares favorably with uncoated steel. long term services. Due to the presence of a zinc layer, steel does not rust, that is, zinc protects the steel base from corrosion.
To create a zinc layer, an electrolytic or hot deposition method is used. Moreover, the latter option is considered more profitable for the production of roofing steel. After pre-treatment, prepared steel plates are immersed in baths of molten zinc. As a result, a protective coating with a thickness of about 0.02 mm is formed on the base.
Advice! Recently, roofing material coated with aluminum zinc has become increasingly widespread. The composition of this coating includes 55% aluminum, slightly more than 43% zinc and less than 2% silicon. This coating reliably protects steel from corrosion and, due to the low cost of aluminum, reduces the cost of the material.
Steel with polymer coatings
To give steel materials a more attractive appearance and provide better protection galvanized steel is coated with a polymer coating. Applying polymer to a steel base is a rather complex process that requires careful control throughout the entire technological process. The steel sequentially goes through several stages of processing; a passivating coating, primer and, only then, polymer are applied to it.
Advice! If polymer metal roofing is used, the roofs look very attractive, since the polymer can be painted in a variety of colors and shades.
Modern manufacturers use different types polymers for application to steel substrates. The most popular options:
- Polyester. This polyester based polymer has the most affordable price and fairly good performance.
- Pural and other polyurethane-based polymers. Such polymer coatings are more resistant to external influences, but not too plastic, so it is not recommended for use on roofs of complex shapes.
- Plastisol is a modern polymer based on polyvinyl chloride. It is applied to the base in the thickest layer (up to 200 microns), so the protective properties of plastisol are very high.
- PVDF – resistant to a wide range of impacts based on polyvinyl fluoride. It is not applied in a very thick layer (up to 50 microns), but provides excellent protective qualities. Its only drawback is its rather high price.
Roofing coverings made of non-ferrous metals
Copper metal roofing is an extremely durable and reliable roofing option. However, due to the high price of the material and installation work it is used quite rarely.
Advice! Copper roofing is interesting because it changes color during use. Freshly assembled coverings have reddish tint. After about a year of use, the coating becomes brown, and even later - almost black. After 20-30 years of use, copper roofing acquires a beautiful malachite green color.
The installation of a metal roof made of aluminum is also relatively rare. Aluminum sheets are mainly used to produce metal tiles, but sometimes seam aluminum roofs are also created.
Zinc-titanium coating is gradually gaining popularity. The basis of the material is zinc sheets alloyed with copper and titanium. The material is distinguished by very high strength and weather resistance, but at the same time, it is almost half the price of copper.
How is a metal roof installed?
Depending on the type of material chosen, one or another installation technology is used. Sheet materials are assembled to form folds, coatings made of non-ferrous metals are mounted by soldering, and metal roofing sheets and metal tiles are secured using roofing screws.
Basics of installing seam roofs
Let's look at how a seam metal roof is assembled:
- When installing such coverings, individual elements are connected to each other to form folds - connections in which the edge of one sheet is wrapped around the edge of another.
- The individual sheets of steel from which the coating is assembled are usually called paintings. In the process of preparing paintings, their edges are folded to create folds.
- When creating coverings, different types of folds are used; connections can be single or double, as well as lying or standing. The most reliable connection is a double standing seam. However, when installing roofing in horizontal rows, it is recommended to use lying seams so as not to create unnecessary obstacles for water flowing down the roof.
- To install or repair a metal roof yourself, you need to have a special tool - folding pliers. A coating made of rolled galvanized steel is considered especially reliable, since this material allows you to prepare pictures that completely cover the length of the slope, which allows you to reduce the number of joints in the coating.
- To attach the paintings to the crate, clamps are used - strips of steel cut from the same material as the paintings. The clamps are bent on one side and nailed to the sheathing using roofing nails at the bend. The second, straight end of the clamp is fastened to the paintings by forming a single fold.
Installation of roofing from profiled sheets
Profiled roofing sheets include metal tiles and corrugated sheets. The installation technology of these materials has many similar features:
- The use of profiled sheets is permitted on pitched roofs with a slope angle of more than 14 degrees.
- When assembling the roof, special shaped elements are used - cornices, gables, ridge strips, elements for arranging valleys and junction points.
- Sheets of profiled material are attached to the sheathing using special hardware - roofing screws. These are screws that have a drill-shaped tip and are also equipped with elastic spacers. During the process of twisting the sheet, the gasket is slightly compressed and reliably seals the attachment point.
- When installing the covering, sheets of material must be laid with an overlap. On slopes with a slight slope in areas of overlap, additionally use sealant for metal roofing.
When assembling any metal roofs, it is necessary to provide for laying a layer of waterproofing, since condensation often forms on the back side of the coating. In the absence of waterproofing, moisture entering inside will destroy the roof structure.
When performing installation, the metal roof must be grounded. This is necessary due to the tendency of metal coatings to accumulate static electricity.
So, metal roofing is a reliable and practical covering. If desired, it is quite possible to install and repair a metal roof with your own hands. Before performing work, you will need to carefully study the technology of working with the selected material.
“Roofing iron” is a simplified name for a category of materials that are attractive due to their light weight, low and relatively low cost. Among the advantages are the large dimensions of the elements, which makes installation easier and increases the pace of roofing work. A very convincing argument is fire resistance and tightness, justified by the complete absence or minimum number of holes for fasteners. It’s not without reason that the list of advantages includes ease of installation, thanks to which the owner can build a metal roof over a country bathhouse with his own hands.
Types of Metal Roofing Sheets
Over centuries of metal use as roofing, many technological variations have been created. Instead of the simplest sheet iron, aluminum or copper, you can now use unique “constructors” produced in factories with a full set of fasteners, additional parts and elements for arranging connections.
The conditional classification of roofing iron divides all currently existing types of metal roofing into the following groups:
- cold-rolled, thin-sheet or rolled, black or galvanized steel, used for the installation of budget seam roofs;
- fully prepared for installation, attracting with an abundant range of modifications of different colors and shapes of elements, and corrugated sheets with similar priorities;
- non-ferrous metals, the group of which includes coatings made of copper, titanium-zinc alloy and aluminum.
Let’s put aside the advantages of convenient and technologically advanced roofing sets made of metal tiles and corrugated sheets due to their high cost. For the same reason, let's temporarily forget about non-ferrous metals. Let's consider the most economical independent device metal roofing, which will require steel sheets with a strip length of 2.50 m and a corresponding width of 1.25 m.
It is recommended to purchase steel for roofing with double-sided galvanization. It is more expensive than its “black” non-zinc coated counterpart, but the money invested in the material will be returned due to rare maintenance and optimized wear resistance. According to the hot-dip galvanizing method, cold-rolled material is completely immersed in containers with molten zinc, as a result of which a dense protective layer is evenly deposited on its surface.
The material thickness values are dictated by the building code: metal roofing (SNiP II-26-76), in accordance with the requirements of building regulations, is constructed from a thin-sheet product from the rolling industry. For roofs, steel with a thickness of 0.5 mm to 1.5 mm is purchased. It will be easier to work with the thinnest sheets; they are easier to bend to form joints. But if the owner plans to make additional parts and drainage elements from the same material, a thickness of 0.6 mm to 0.8 mm is recommended.
Please note. Building rules do not prohibit, but also do not recommend, distorting the shape of galvanized sheets, as a result of which the integrity of the zinc coating may be disrupted. According to the requirements of SNiP number 3.03.01-87, metal tools during work cannot be placed on a galvanized surface without a wooden lining. Damage to the zinc protection will cause loss of performance.
Independent device and installation
The most common and economical type of laying metal sheets on the roof is called seam technology. The name and principle of construction is based on the method of connecting elements with repeatedly curved edges, forming longitudinal and transverse seams - folds.
- Transverse seam connections are used if the horizontal size of the slope exceeds standard length steel sheet 2.5 m. They can be single or double, they are called horizontal because they have the same direction, and recumbent because they are bent towards the drainage of water from the roof, so as not to create barriers to the spontaneous flow of precipitation.
- Longitudinal seam seams connect the roofing elements along the imaginary vertical of the slope, that is, along the side line of the sheet. They are not bent because they do not obstruct the flow, which is why they are called standing. By analogy with the previous connections, they can be double or single. Not a single installation of metal roofing using seam technology is complete without horizontal standing joints.
Horizontal connections, especially if they are single, reduce the ability of the structure to resist atmospheric negativity. If possible, it is advisable to exclude them. Standing double seams are recognized as the most reliable and practically airtight. You can form a seam either with a hammer and a wooden screw, or with the help of special electromechanical seam rolling machines or manual comb benders.
Specifics of standing seam roof construction
Its main element is the picture. This is a part assembled from two adjacent steel strips with curved edges necessary for subsequent connection. The paintings are collected on the ground. To assemble them, it is advisable to make a special workbench with a length equal to the length of the parts of the picture to be connected.
To splice the paintings and attach the outer panels to the sheathing, you will need homemade clamps - strips cut from the same steel with side dimensions of 3 and 15 cm. They are attached every 0.5 m next to the vertical seam line. Considering this fact from scraps of steel sheet you need to make required quantity fasteners
Attention. Galvanized steel parts are cut with scissors. The grinder leaves an uneven jagged edge and burns out the protective coating.
The paintings, assembled in a safe environment with the edges prepared for joining, are lifted up, but first the base for their installation is prepared.
Construction of the rafter system and sheathing
The rules for constructing a rafter system for a metal roof are no different from the technologies for constructing frames for other roofs. Only due to the lightness of the material, it is not necessary to be careful with the location of the rafters. However, given the ability of the metal to sag under the weight of human weight, the sheathing beams are installed at intervals of 20 cm. This step will prevent damage to the coating, since the foot of a person climbing onto the roof for repairs or maintenance will invariably rest on the sheathing.
According to building regulations, the minimum slope of metal roof slopes is 14º, the maximum value is 30º. For flat roofs, the installation step of the slats will have to be reduced; it is even better to make a continuous covering from edged boards.
If the roof is insulated and waterproofing is laid over the sheathing, a counter-lattice made of thin slats is required to form a ventilation gap between the metal covering and the insulating layer. Thanks to ventilation, there will be an equal temperature on both sides of the roofing material, which means there will be no condensation that destroys the metal and no icicles on the eaves.
The eaves overhang is made of 3 or 4 solid boards. The ridge is formed by laying boards on both sides, converging at a single point.
Assembly of seam roof elements
Gather metal fencing roofs begin with the installation of special crutches, installed along the eaves overhang every 70 cm. Initially, two crutches are nailed along the edges, a cord is pulled between them to align the remaining parts. Crutches nailed along the base of the overhang can replace the crutches. metal corner with a side of 4-6 cm.
Attention. To cross the ridge, a 3 cm edge should be left on one side and 6 cm on the other.
- The paintings, made up of two metal strips, are transported by car lift to a storage area specially organized for them at the top.
- First of all, along the line of location of the second picture, clamps are attached with self-tapping screws every half meter. The clamp must be positioned so that its fixation point is covered by the picture laid on top.
- Then the first picture is installed, the side line of which coincides with the line of the pediment. The first element is fastened through the pediment line with self-tapping screws.
Attention. Ordinary paintings have edges of different heights, usually one is 5 cm, the second is 2.5 cm. The first strip has both edges of 2.5 cm.
All elements of a seam roof are mounted according to a similar scheme: first, clamps for the next strip, then installation of it itself and connection with the previous strip. The fold is folded together with homemade fastening strips. Thanks to the installation of clamps, simultaneous fastening is carried out both to the sheathing and to adjacent elements. Experienced roofers advise strengthening seams with silicone sealant.
Advice. To prevent unbending of homemade clamps, you can add a riveting to the point where they are located in the horizontal seam.
- Upon completion of the merging of the seams, the joints must be sealed using a hammer and a strip of metal.
- Then the smaller edge is folded over and secured to the ridge, and the larger ridge edge is placed and secured on top of it.
If the galvanized surface is not suitable for aesthetic reasons, it can be primed with pigmented drying oil and then painted.
Lightning protection
There is an opinion that a metal roof does not need a protection device, because it is a natural lightning rod. However, a direct lightning strike can still cause a fire due to overheating of the metal installed on the wooden sheathing. If the seams between the covering elements are sufficiently reliable, lightning protection of a metal roof is carried out by connecting it through a down conductor to the grounding system. If there is an electrical connection between the covering elements, pin and torso lightning rods can be dispensed with.
The construction of a metal roof is the simplest and most economical way to arrange a country bathhouse. If all stages are carried out according to technological rules, the roof will last more than 20 years, without requiring alterations or repairs. It is important to take into account the features of the metal coating and not forget about the installation rules.
There are a lot of building materials on sale now. You should choose a roof covering that suits your needs. Metal roofing is considered one of the most reliable. This material, which the plant produces, can be used for more than 20 years without repair. He is more reliable than others. Perhaps, on the ground, at a certain stage of the work, it will be necessary to make a truss.
In this article
We make sheathing with rafters
We will be installing rafters for a standing seam roof. The technology is simple and understandable. There is no need to install rafters here often, since the material is light.
Make the sheathing from timber. The step needed is from 200 to 500 mm. This will help in the future to minimize the deformation of the roof, when you repair something, walk on the roof, the sheet metal will not bend. The required timber thickness is 50 by 50 or 50 by 100 mm. Depending on what kind of roof you have, you may need to make trusses on the ground.
The roofer, who begins to move on the roof, will step with his feet on the metal, and under it, the sheathing of the board. The coating technology is safe, standard project. With a flat roof, the sheathing will turn out similarly to flat. The ridge is made from 2 boards, 2 of their edges are reduced to 1 point. For the cornice, 3 or 4 boards are nailed together and it comes out solid.
We provide waterproofing
If you do not want the back side of the metal roof to become covered with condensation, you must first do high-quality waterproofing. With an insulated roof, the sheathing is nailed to the rafters. You can start making a truss on the ground or simply place a waterproofing superdiffusion membrane on top. It will not let moisture in, and steam will come out freely.
Waterproofing is done from the bottom of the roof and gradually raised. At joints an overlap of 100 to 150 mm is required. These places are glued together using construction tape. The film is attached so that it sags a little. During severe frosts, the material narrows and it will not tear, being strongly stretched from one fastening to another.
In addition to fastening with nails, this can be done using dowel nails with a wide head. This is done with self-tapping screws. A counter-lattish is placed on top of the waterproofing membrane. She has the same step as mentioned above. You will get 2 gaps for ventilation: the 1st between the waterproofing and insulation, the 2nd between the metal surface of the roof with the waterproofing.
We fix the metal roof
Installation of iron sheets on the roof begins with the installation of crutches. They need to be nailed to the eaves, taking steps of 70 cm. This will help hold the metal pictures and they will not fall from the roof during installation. Let's consider the installation technology:
- Some people take a steel corner instead of wooden crutches. 50 to 60 mm is enough and it is fastened along the eaves, on the overhang. This method is even more convenient in some ways; there is no need for the crutches to be positioned strictly on the same line.
- The first of the paintings is lifted up. Its edges are already bent and laid near the pediment. It is necessary that there is an overhang of 40 to 50 mm. Align the sheet so that when passing through your ridge, you get a 30 mm edge. On the opposite slope, a 60 mm edge is required.
- The clamps are attached to one of the sides; there will be 2 metal sheets located there. The clamp is attached to the sheathing using a 4 by 50 mm self-tapping screw. The attachment point will later be covered with a metal sheet.
- It will turn out that the metal edge, which is bent, will be near the edge of the clamp, located vertically. There will be a step of 500 to 600 mm between fastening the clamps. We continue the installation.
- We lift the 2nd picture and place it near the 1st so that its edge, which is folded, falls on the similarly curved edge of the 1st. If the edges of 2 canvases are without bends, then they need to be placed one next to the other.
- Place a clamp between the sheets and clamp. Now take roofing frames or other tools and make a fold. Walk in one direction and back manually with the tool and you’ll be done. Inside the fold you will need to bend the clamp and they will be connected very tightly.
- Important! Do you live near a pond? Then, to prevent the metal roof from rusting in places, the joints on the roof must be additionally coated with sealant. A special sealant for metal roofing is sold in a supermarket or construction market.
- Tytan silicone sealant is good. Apply it to the fiberglass strip. It should be as wide as the edge you folded. Before joining the seam, you need to glue this strip to the metal edge.
- On the other edge of the 2nd of the paintings you need to nail the clamps in the same way. Pick up the 3rd picture and do the same standard process as before. In areas where the paintings will be adjacent to the gables, you need to attach a side wind strip, and then a side strip that will be located on top. These elements are secured either with self-tapping screws or seam joints, which is considered difficult and is not recommended for beginners to do on their own.
- When you have laid all the metal sheets on both sides of the slopes, secure them and you can install the ridge. Make it unvented or vented. Ventilation can be done in several ways. A metal roof with a ridge looks more beautiful, and trusses will help you install the roof faster.
- The last to be made are the eaves overhangs, and on them the soffits for the roof. Next, the gutters are secured to allow rainwater to drain. For a seam painting, the edge is turned down and the water flows freely.
- Roofing paint for sale. You can choose the color you like and cover the roof with it. In warm weather the paint will dry quickly.
- If your house has 2 floors or more, then you will need a fire escape for safety. Attach it securely to the roof and vertical wall of the house. The ladder will save the life of you and your household during a fire.
Installing snow guards
On a seam roof, snow guards with guards must be installed. This is stated in clause 8.11. according to SNiP 21-01-9. In winter, snow guards will prevent snow from falling down from the roof with a roar like an avalanche. After all, people passing below can get injured.
Spare parts for snow guards need to be secured to folds that stand vertically. You will need screws or a self-tapping screw. Using profile pipes, a fence is erected.
Installing lightning strike protection
Some experts believe that there is no need to make any special lightning rod for a metal roof, because a metal roof is a natural lightning rod. But don't forget that there is a wooden grate underneath. She could catch fire, followed by the whole house.
If the seams between the roof sheets are reliable, then you can attach a down conductor to it, and connect it to the grounding system. If there is an electrical connection between the roof elements, then you do not need to use cable or pin lightning rods.
At all stages of roof construction, adhere to technology. If private owners do everything correctly, then such metal roofs will last them 20 years or more. Nothing will need to be repaired or remodeled.
Do not forget that if necessary, you can make blanks on the ground - trusses and lift them and install them on the roof. Some make metal soffits or wood. Purchase all materials and produce finishing materials at your discretion. You live in this house.