01.10.2010, 11:47
calculation:
1) beam 200*200*6000 through 0.5M = 22 t.r (deflection 20 mm)
2) I-beam 20B h/w 1.2 m = 27 tr. (deflection 20 mm)
By weight 1) -90 kg timber, 2) - 120 kg beam
In theory, the solutions are very similar. I'm interested in practice, which is better?
Green Cat
01.10.2010, 11:55
Beam.
In general, you shouldn’t use iron to make any load-bearing structures, because in a fire, the tree holds out until the last, and the iron is cracked and ready.
01.10.2010, 15:55
The temperature at which the I-beam will deform is incompatible with life. Especially if the bottom is covered with plasterboard.
If you still decide to make it with wood, then I recommend 200x60x6000 with a step of 600 mm.
01.10.2010, 16:55
“Crack and it’s done” - but won’t it matter anyway)))
It can be deformed in one place and fly to another, where there are still conditions for life... :) but in general you are right.
+Wood itself will support combustion, but iron will not...
Green Cat
01.10.2010, 17:41
The temperature at which the I-beam will deform is incompatible with life.
Wrong.
It’s one thing when he’s on his own, and another when he’s under load.
Until recently, it was generally prohibited to use meth as rafters. profile, now I see they are doing it with all their might.
I recommend 200x60x6000 with a pitch of 600 mm
It will be too small, too small - let's look at the cuckulator.
01.10.2010, 20:32
In one room I had a span of 5.7 meters, the overlap between the 1st and 2nd floors. I chose an I-beam 20B at 1.3 meters, it seems that according to calculations the I-beam was stronger than wood. It is worth considering that a tree can be found 6.5 meters long, and the length of an I-beam is 11.7 meters or 12 meters (to cover a span of 6 meters you need at least 15 cm on one side). It would have been better to lay the slabs, but I didn’t succeed. The difference between the tree and the I-beam was somewhere around 10-12%. When laying the walls, I installed 3 cm of foam between the cutout in the gas block and the I-beam.
Regarding the fire, you need to take precautions.
02.10.2010, 00:47
And I laid a 5.8 meter reinforced concrete slab on the 6 m span and don’t think about anything else. Doesn't burn, doesn't melt, doesn't bend...
02.10.2010, 09:00
Thanks to everyone, I’m still leaning towards an I-beam, since it’s stronger, I want to install internal walls made of 100 cm foam block for the ceiling. (although it was probably possible to put 2 beams under the wall)
then wawan001 the span is 6M along the axes of the walls, that is, there will be 15 cm of support on each side.
then Cat, I guess if you fill in non-flammable insulation ala expanded clay, then there will be nothing to burn there at all (the house is made of foam blocks).
And another question, if you cover it with an I-beam, is it possible to use, say, a 50 piece of wood attached to the side walls instead of the outer beams??
02.10.2010, 18:30
There is another option.
02.10.2010, 19:12
There is another option.
You make a load-bearing beam (albeit from an I-beam), on which you lay simple wooden floor beams. It will be much cheaper.
You will need one or two I-beams, but powerful ones. The price will still be cheaper.
I did it to myself
02.10.2010, 20:01
dengt, this idea came to my mind from the point of view of the manufacturability of installing floors in the future, if wooden floors are installed inside the I-beam, and a counter-lattice is made on top (beams according to calculations). The distance from the edge of the beam to the I-beam is 40 cm - reliable. After all, according to calculations, the load on the outermost beams is 2 times less than on the adjacent one, you can put a 150x200 beam or take 2 pieces of 50x200 boards and between them install pieces of boards of the same size 1.5 meters long, and I think 50 is flimsy, although if to It can be attracted to the wall and it will be fine. If you are confident in the fasteners, then probably yes.
04.10.2010, 05:57
I covered the span with a 5m beam of 150*150, folded in half and tied with pins, i.e. The result is a beam 150*300. It turned out pretty tough, but I would still make it out of concrete if possible :(
05.10.2010, 09:32
[
I did it to myself
the span is 11 by 6, divided into three parts by two I-beams and laid wooden beams, and in order not to increase the thickness of the ceiling, laid them inside the T-beam. I first welded the corners to the tee and secured the beams with bolts.
As I understand it, the I-beams were 6 meters high?
here you need at least 25B2, it’s a 5 cm thicker covering, it doesn’t seem to be fatal.
What worries me about attaching the side beams to the walls is that all the other beams will sag, but the outer ones will not, then the floor will bend in a “bubble”? What will this lead to?
05.10.2010, 10:11
6-measure I-beam 20B1 - two pieces across the length, it turned out 3 zones, two with beams resting on one side on the wall, and the other on the I-beam, and one zone with beams sandwiched between the I-beams. I didn’t notice any flexing; the I-beam doesn’t work at that length.
06.10.2010, 13:06
06.10.2010, 13:47
depending on how you load it, if according to theory it’s 400 kg/m then in your case the 20B1 will bend by 77 mm
I wonder how you calculated this?
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Among the many structural elements In a private house, the ceiling is one of the most important and difficult components to design and install. This is where inexperienced builders make, perhaps, the most dangerous mistakes; it is about the arrangement of this system that the most questions are asked.
1. Why choose a tree
In any building, the ceiling is a horizontal structure that serves as the basis for creating the floor. In addition, being connected to the load-bearing walls of the house, it provides lateral stability to the structure, evenly distributing possible loads. Therefore, the highest demands are placed on the reliability of this design.
Regardless of what material is used in the construction of a house, wooden floors are most widespread in the private sector. They can often be seen in various stone cottages, and it is quite obvious that in wood construction(log, timber, frame and frame-panel technology) there is no alternative to such a decision. There are many objective reasons. Let's look at the advantages and disadvantages of wood floors.
In private low-rise construction, floors are installed in several options:
- Ready reinforced concrete slab,
- Monolithic reinforced concrete slab,
- Ready-made reinforced concrete beams,
- Beams and trusses made of rolled metal,
- Flooring made of lumber.
pros
Or why wooden floors are so popular.
- Small mass. When using a board or timber, we do not overload load-bearing walls and foundation. The weight of the ceiling is several times less than that of concrete or metal structures. Usually no technology is required.
- Minimum deadlines for completing work. Minimum labor intensity among all options.
- Versatility. Suitable for any building, in any environment.
- Possibility of installation at sub-zero and very high temperatures.
- No “wet” or dirty processes.
- Possibility of obtaining any level of thermal insulation and sound insulation characteristics.
- Possibility of using cavities for gaskets engineering communications(power grid, heating, water supply, sewerage, low current...).
- Relatively low price of prefabricated frame floor from lumber, both in terms of the cost of parts/components and the contractor’s wages.
Minuses
The disadvantages of a wooden ceiling system made of wood are quite conventional.
- Difficulty in choosing the cross-section of materials and constructive solutions to ensure the calculated load-bearing capacity.
- The need to carry out additional fire prevention measures, as well as provide protection from moisture and pests (antiseptic treatment).
- The need to purchase soundproofing materials.
- Strict adherence to technology to avoid construction errors.
2. What material to use for assembly
Wooden flooring always consists of beams. But they can be made from a variety of lumber:
- Rounded log up to 30 cm in diameter.
- The beam is four-edged.
- Large section board (thickness from 50 mm, width up to 300 mm).
- Several boards of relatively small thickness, twisted face to face.
- I-beams, the upper and lower chords of which are made of edged planed boards/bars, and the vertical wall is made of OSB-3, plywood or profiled metal (wood-metal product).
- Closed boxes made of sheet materials (plywood, OSB).
- SIP panel. In essence, these are separate sections in which the beams are already sheathed and have an insulator inside.
- Various truss designs, allowing to cover large spans.
The easiest options for installation, as well as the cheapest and most convenient for subsequent operations, are those where the floor beams are made of edged lumber.
Due to the very high requirements for load-bearing capacity, durability and geometric deviations, first-grade lumber must be considered as blanks. It is possible to use products classified as second grade according to GOST, which do not have critical geometric deviations, defects and processing defects that can reduce strength characteristics and service life finished parts(through knots, twists, cross-layers, deep extended cracks...).
In these structures, the use of dead wood (dead wood, dead wood, burnt wood) is excluded due to insufficient strength and multiple damage to wood-destroying diseases and insects. Also big mistake will buy a beam or board “with air”, “with Armenian size”, “TU” - due to the reduced sections.
It must be exclusively healthy material from green spruce or pine, since needles, due to their resin content and the structure of the massif, withstand bending loads and compression much better than most hardwoods, and having a relatively low specific gravity.
Anyway edged lumber must be freed from remnants of bark and bast fibers, treated with an antiseptic and fire retardant. Dry planed lumber will perform best here, but material with natural humidity (up to 20 percent) during normal processing is also actively (and most importantly, effectively) used, especially since the price of edged timber or boards of this type is noticeably lower.
3. How to choose the size of beams and at what step to arrange them
The length of the beam is calculated in such a way that it covers the existing span and has a “margin” to provide support on load-bearing walls (read below for specific figures for permissible spans and wall penetration).
The cross-section of the board/beam is determined depending on the design loads that will be exerted on the floor during the operation of the building. These loads are divided into:
- Permanent.
- Temporary.
Temporary loads in a residential building include the weight of people and animals that can move along the floor, moving objects. Constant loads include the mass of the lumber of the structure itself (beams, joists), floor filling (insulation/noise insulation, insulating sheets), hemming (rolling), rough and finishing flooring, finishing flooring, partitions, as well as built-in communications, furniture, equipment and household items...
Also, you should not lose sight of the possibility of storing objects and materials, for example, when determining the load-bearing capacity of the floors of a non-residential cold attic, where unnecessary, rarely used things can be stored.
The sum of the permanent and live loads is taken as a starting point, and a safety factor of 1.3 is usually applied to it. Exact figures (including the cross-section of lumber) must be determined by specialists in accordance with the provisions of SNiP 2.01.07-85 “Loads and impacts”, but practice shows that the load values in private houses with wooden beams turn out to be approximately identical:
- For interfloor (including under a residential attic) and basement floors, the total load is about 350 - 400 kg/m2, where the share of the structure’s own weight is about 100 kilograms.
- For covering an unloaded attic - about 130 - 150 kg/m2.
- For covering a loaded non-residential attic up to 250 kg/m2.
It is obvious that unconditional safety is of paramount importance. Here a good margin is taken into account and the option is considered not so much of distributed loads on the entire floor (in such quantities they are practically unrealistic), but rather the possibility of a local load that can lead to deflections, which in turn caused:
- physiological discomfort of residents,
- destruction of components and materials,
- loss of aesthetic properties of the structure.
By the way, certain deflection values are allowed regulatory documents. For residential premises, they can be no more than 1/350 of the span length (that is, 10 mm at 3 meters or 20 mm at six meters), but provided that the above limiting requirements are not violated.
When choosing the cross-section of lumber to create a beam, they are usually guided by the ratio of the width and thickness of the beam or board in the range of 1/1.5 - 1/4. Specific figures will depend, first of all, on: loads and span lengths. At independent design You can use data obtained from calculations using online calculators or publicly available tables.
Optimal average cross section of beams wooden floor, mm
As we can see, to enlarge load-bearing capacity ceilings - it is enough to choose lumber with a larger width or greater thickness. It is also possible to assemble a beam from two boards, but in such a way that the resulting product has a cross-section no less than the calculated one. It should also be noted that the load-bearing properties and stability of a wooden floor increase if logs or various types of subfloors are used on top of the beams (sheet flooring made of plywood/OSB or edged boards).
Another way to improve the strength properties of a wooden floor is to reduce the spacing of the beams. In their designs for private houses, engineers determine under different conditions the distance between beams from 300 mm to one and a half meters. IN frame construction The pitch of the beams is made dependent on the spacing of the posts, so that there is a post under the beam, and not just a horizontal frame run. Practice shows that the most appropriate from the point of view of practicality and cost of construction is a step of 600 or 1000 mm, since it is best suited for the subsequent installation of insulation and noise insulation by surprise (insulating materials have just such a form factor of plates and rolls). This distance also creates optimal distance between support points for mounting floor joists installed perpendicular to the beams. The dependence of the cross section on the pitch is clearly visible from the numbers in the table.
Possible cross-section of floor beams when changing the pitch (total load on square meter about 400 kg)
4. How to properly install and secure beams
We have decided on the step - from 60 centimeters to a meter will be the golden mean. As for spans, it is best to limit yourself to 6 meters, ideally: four to five meters. Therefore, the designer always tries to “lay” the beams along the smaller side of the house/room. If the spans are too large (more than 6 meters), then they resort to installing load-bearing walls or support columns with crossbars inside the house. This approach makes it possible to use lumber of a smaller cross-section and increase the spacing, thereby reducing the weight of the floor and its cost for the customer with the same (or better) load-bearing characteristics. As an option, trusses are created from lighter lumber using metal perforated fasteners, for example, nail plates.
In any case, the beams are placed strictly horizontally, parallel to each other, maintaining the same pitch. The wooden beam must rest on load-bearing walls and purlins by at least 10 centimeters. As a rule, use 2/3 thickness outer wall from the side of the room (so that the end of the beam does not go out onto the street and remains protected from freezing). IN wooden walls they make a cut, in stone ones they leave openings during laying. Where the beams touch load-bearing structures it is necessary to lay insulating materials: damping elastic pads made of rubber/felt, several layers of roofing felt as waterproofing, etc. Sometimes they use firing of sections of the beam that are subsequently hidden or coating them with bitumen mastics/primers.
Recently, special perforated brackets “beam holders/supports” have been increasingly used to create floors, which allow the beam to be mounted end-to-end with the wall. Using this type of brackets, units with transverse crossbars and beams truncated in length are also assembled (an opening for flight of stairs, chimney passage, etc.). The advantages of this solution are obvious:
- The resulting T-shaped connection is very reliable.
- The work is done quickly (there is no need to make cuts, it is much easier to set a single plane).
- No cold bridges are formed along the body of the beams, because the end is moving away from the street.
- It is possible to buy lumber of shorter length, since there is no need to insert the timber/board inside the wall.
In any case, it is very important, after adjusting the lumber to size, to thoroughly antisepticize the end of the beam.
5. What insulating layers should be used inside wooden floors
To answer this question, first of all, it is necessary to divide the overlapping structures (in a year-round habitable house) into three separate types:
- Basement ceiling,
- Interfloor,
- Attic.
In each specific case, the set of pie will be different.
Interfloor ceilings in the vast majority of cases separate rooms in which temperature regime similar or close in value (if there is room/floor/zone adjustment heating system). These also include the attic floor, which separates residential attic, since this room is heated, and the insulation is located inside roofing pie. For these reasons, thermal insulation is not needed here, but the issue of combating noise, airborne (voices, music...) and shock (steps, rearranging furniture...) becomes very relevant. As sound insulation, acoustic fibrous materials based on mineral wool are laid in the ceiling cavity, and sheets of sound-proofing membranes are also laid under the sheathing.
The basement design assumes that under the ceiling there is soil or a basement, cellar, ground floor. Even if the room below is equipped for use, this type of floor requires full insulation, characteristic of the enclosing structures of a specific climate zone and a specific building with its unique thermal balance. According to standards, the average thickness for the Moscow region modern insulation with good thermal conductivity will be about 150-200 mm.
Similar thermal insulation requirements apply to attic floor, above which there is no heated attic, because it will be the main barrier to heat loss through the roof of the building. By the way, due to the greater flow of heat through the upper part of the house, the thickness of the insulation here may be required more than in other places, for example, 200 mm instead of 150 or 250 mm instead of 200.
They use polystyrene foam, EPS, mineral wool with a density of 35 kg/m3 in slabs or cut into mats from a roll (one that is allowed for use in non-load-bearing areas is suitable horizontal structures). Thermal insulation is laid between the beams, usually in several layers, with the joints bandaged. The load from the insulation is transferred to the beam through the rough hemming (often it is attached to the beams using cranial bars).
Where wadding insulation/sound insulation is used in structures, it should be protected from moisture. In the basement, moisture can rise in the form of evaporation from the ground or from the basement/cellar. IN interfloor ceilings and attics, water vapor can enter, which always saturates the air in residential premises during human daily activities. In both cases, underneath the insulation you need to lay construction material vapor barrier film, which can be ordinary or reinforced polyethylene. But, if thermal insulation is performed using extruded polystyrene foam, which does not have any significant level of water absorption, then a vapor barrier will not be needed.
On top, insulation and fibrous soundproofing materials are protected with waterproof sheets, which can be membranes or non-perforated waterproofing.
A reliable water barrier is especially relevant in rooms with high humidity: kitchen, laundry room, bathroom... In such places it is spread on top of the beams, always with the strips overlapping by 100-150 mm and gluing the seam. The canvases along the entire perimeter of the premises must be placed on the wall - to a height of at least 50 mm above the finishing coating.
The ceiling, which will later be lined tiles, it makes sense to supplement with rough flooring made of waterproof sheet materials - various types cement-containing slabs, preferably tongue-and-groove. On such a continuous flooring you can carry out additional coating waterproofing, perform thin-layer leveling of the plane with a leveling compound or lay the tiles immediately.
You can choose another option - collect from edged boards continuous flooring, lay a hydraulic barrier, pour a thin-layer screed (up to 30 mm), install tiles.
There are also modern adhesive compositions(and elastic grouts) allowing tiling wooden bases, including movable and heated ones. Therefore, tiled floors are often sold here on moisture-resistant plywood or OSB.
Important! Taking into account the increasing loads (general or local - a large bathtub, a Jacuzzi bowl, a floor-standing boiler...), the calculation of the cross-section and pitch of beams under such rooms must be performed individually.
If desired, floors in the bathroom or kitchen wooden house can be equipped with a heating cable or pipes of the water circuit of the heating system. They are mounted both in screeds and a layer of tile adhesive, and between joists in a deliberately created air gap. With any chosen option, the ceiling must be well insulated so as not to heat the ceiling of the room from below, preferably equipped with waterproofing with a reflective foil layer.
