Mistral prefabricated roof trusses.
From the series "Roofs, roof accessories - trends 2023".
The truss is the basic element of the roof structure. A sufficient number of trusses together constitute a roof truss. Among other things, the task of the roof truss is to ensure that the loads generated from the weight of the structure, roofing, snow and wind are safely transferred to the wall structure. Roof trusses - in summary - are a type of properly prepared prefabricated roof truss.
We talk to an expert about this technology.
Today we'll touch on the topic of roof trusses and talk to an expert on the subject. Please introduce yourself.
Jacek Wisniewski. I am the sales director at MISTRAL KWIATKOWSKI I WSPÓLNICY. By education I am a wood technology engineer with nearly twenty-five years of experience.
So here we go with our topic of the month - roof trusses - what are they and what are they used for?
A truss is the basic element of a roof structure. A sufficient number of trusses together constitute a roof truss. Among other things, the task of the roof truss is to ensure that the loads generated from the weight of the structure, roofing, snow and wind are safely transferred to the wall structure. Roof trusses - in summary - are a type of properly prepared prefabricated roof truss. We manufacture them based on MITEK's barbed plate technology. A complete roof built from trusses provides investors with a safe roof over their heads.
prefabricated roof trusses
© Mistral
Barbed tiles... what is that? - please explain to your readers.
Barbed plates are a technology for joining wooden elements without nails. The technology was developed in the USA in the mid-1950s. The technology came to our country in the early 1990s, with the opening of Poland to the West. Since then we have seen an increase in the share of prefabricated trusses in the construction market.
So how to take care of the right quality of trusses on our roof, what to pay attention to?
First of all, the design. It is up to the knowledge of the Architect to decide exactly what solution he will propose. The investor in many cases does not have enough knowledge to verify the technical solutions used in a given project. Replacing traditional heavy ceilings with a prefabricated truss roof with a wooden bottom chord is a particularly desirable solution. It not only speeds up the construction of the house, reduces the cost of construction by eliminating the ceiling, which is unnecessary in a one-story house, but most importantly improves the insulation capabilities, which in times when energy costs are high, is particularly desirable.
Another thing you need to pay attention to is the proper conversion of truss load capacity to the corresponding snow zone, i.e. a different, lighter truss will be needed in Zielona Gora than in Suwalki. This is due to the climate zone and the norms set for it. Thanks to this procedure, we can reduce the cost of the structure by several to a dozen percent.
The next important element that an investor should pay attention to is a certified material with the right strength and moisture content of wood. Ideally, the manufacturer should be CE-certified for the manufactured roof trusses. An investor who chooses a certified manufacturer is guaranteed that the production process of his trusses is monitored from the moment the project is sent to production until it leaves the factory.
prefabricated roof trusses
© Mistral
And what is the process of preparing roof trusses like?
I don't know how it is in other companies - I can tell you how it looks in our company. You can divide the whole process into several stages. First, a potential customer sends a project for a quote. Our designers develop a preliminary design of the roof trusses and send a cost estimate. After its approval, a contract is signed. Well in advance, a production project is prepared, which is directed to two departments. To the cutting and folding department. In the cutting department, using digitally controlled saws, truss components are cut and assembled into individual trusses. Then the package of cut elements prepared in this way goes to the impregnation bath. The impregnant protects the surfaces against the harmful effects of: fire, household and mold fungi and insects. After impregnation, the elements go to the press folding department. We have something to boast about - our press is a very modern device. We have developed our own innovative system for magnetic positioning of barbed plates. The elements are assembled into individual trusses. Automation of the production process ensures the expected quality of the final product. The finished trusses are completed, loaded onto transport platforms and shipped to the customer. Together with the roof, an assembly team also arrives at the construction site. We prefer to do the assembly with our own specialized teams to exclude the possibility of mistakes. Prefabricated trusses are assembled in a very short time. Assembly usually takes one day.
prefabricated roof trusses
© Mistral
What materials should be used for production ? What should you pay attention to?
I will not be revealing here - quality works wonders. Wood should be certified in class C24, it should be heat-dried and four-sided planed. The most commonly used wood is spruce. It should not have visible knots, non-uniform fiber routing, knot defects or cracks reaching the edges. I spoke at the beginning about proper drying. Drying the wood eliminates any biological pests that may have been in the log, and at a later stage of use of the dried material, the removal of moisture and the change in the protein structure of the wood means that pests do not feed in the material. I also talked about four-sided planing. The purpose of planing is primarily to make the wood more difficult to ignite, since fire, in the event of a fire on a smooth surface, has a harder time penetrating. Barbed boards are supplied by several manufacturers. The largest is MITEK and we use them.
prefabricated roof trusses
© Mistral
What are the advantages and disadvantages of trusses?
The use of prefabricated trusses in the construction process has many advantages and virtually no disadvantages. Until recently, the biggest disadvantage of prefabricated construction was its price. Carpentry solutions were often cheaper. For several years, we have seen a narrowing of the price gap. This is mainly due to the significant increase in labor costs and the increased awareness of Investors who do not want to have a roof made of freshly sawn wood of unknown origin.
Well, everyone praises the technology they use - please be more specific....
- We prepare an individual design of trusses, adapted to the location of the building, taking into account all the conditions required to be met in the location, additionally adapted to the roofing and other loads assumed by the investor.
- We use certified materials, much less material consumption is saving the environment and your pocket.
- We have the ability to generate loft space in the truss space
- Execution of both simple and complex multi-truss roof structures with accuracy unavailable for traditional trusses.
- Millimeter accuracy in the execution of individual trusses. This is a particularly important aspect for flat tile roofing, where every unevenness is extremely visible.
prefabricated roof trusses
© Mistral
I am most convinced by the lower material consumption and the possibility of saving additional space in the attic, the rest of which good roofers can handle perfectly.
Yes, but for a good roofing team sometimes you have to wait a year, while we will complete the order in a few weeks.
Okay, so when is it worth using trusses?
In any case, it is worth considering the use of prefabricated trusses. In commercial construction, this is a solution often used by builders, as the span of trusses can reach up to 30 meters without support. It is also an ideal solution in agricultural construction, where building conditions eliminate the use of steel structures. However, the largest market for prefabricated trusses is residential construction.
prefabricated roof trusses
© Mistral
What types of roofs are trusses used for?
In residential construction, the most cost-effective use of trusses is for a one-story building. In this case, there is no need for a ceiling. The building is finished with a rim, to which roof trusses with a bottom chord are mounted. Whether it is a mono-pitched, gabled or envelope roof, this solution is an incredible time and money saver. In the space of the trusses we can generate attic space with a load capacity of up to 150 kg/m²! A similar solution can also be used in multi-story buildings where we do not have a usable attic. Another type of buildings, are buildings with a usable attic. In this case, we usually have a wooden ceiling and a fully usable attic. The last type of use of prefabricated trusses are superstructures on existing buildings. Thanks to the use of lightweight framing technology, this is often the only method of superstructure without the need for costly foundation reinforcement.
prefabricated roof trusses
© Mistral
Mr. Jack, let's recap. What are the most common mistakes you observe during their installation, what to pay special attention to?
The roof is an essential element of the building. Performed badly, it can pose a danger to users. Prefabricated technology eliminates the most common mistakes, such as the use of inappropriate materials and inaccuracies in workmanship. The most common errors are due to two factors - man, as a fallible person, and the quality of the materials used. The investor should avoid a situation in which the team, with the help of primitive tools, cuts the elements on site. Here it is extremely easy to make a mistake. The second danger that should be absolutely avoided is when the team conducts work "their own way", this applies to teams "knowing better than the designers" and assurances "we have been doing roofs for 20 years and none have broken yet". In the era of climate change, violent weather events, the roof begins to take quite a lot of force. Prefabricated trusses are much more densely spaced compared to traditional trusses, which increases the number of points of attachment of the roof to the rim, and thus significantly increases the level of safety of the roof from being torn off by strong winds. Therefore, I urge all investors to opt for prefabricated solutions supplied by certified factories.
prefabricated roof trusses
© Mistral
I don't believe that all truss manufacturers are so perfect... and I know really good roofing teams that don't use this technology
Yes, it's true, also among the truss manufacturers there are some incorrectly made roofs. I urge every investor to check what kind of machinery the manufacturer has at its disposal. In recent years, a lot of small companies have sprung up that try to produce trusses in workshop conditions - former barns without specialized equipment.
Among the most common manufacturing errors is the repositioning of the barbed plate in the gusset. This is a significant error that can weaken the joint and, in extreme cases, can lead to the failure of the truss. An equally common mistake is over-weighting the structure to reduce the amount of material used. CE-certified plants do not use such practices, and as a long-time participant in the construction market, I recommend that every investor consider whether saving a few hundred zlotys is worth the risk.
The next category of errors are those related to installation. It is very important that the manufacturer has trained and experienced installation teams. The execution of the installation must be in accordance with the installation design supplied with the trusses. The most common mistakes: unevenly linear installation of trusses (causing curvature of the roof slope), particularly safety-threatening deviation from the axial alignment (skew) of trusses, deficiencies in bracing, insufficient number of screws/nails in fasteners.
prefabricated roof trusses
© Mistral
We spoke with Jacek Wisniewski, a master engineer of wood technology. Thank you for the interesting conversation and advice to our readers.
Thank you also for being able to share your experience.
For more information, visit the company's {tag:Manufacturer} page on the PdA portal.
