- Structural behavior of plasterboard plating
- Cleaning and preparation of seams
- Special end treatment
- Materials for strengthening the seam
- DIY seam
It is difficult to overestimate the importance of the correct sealing of the joints between the plasterboard sheathing sheets. Today we will figure out what recommendations are given by the leading manufacturers of drywall, and also describe the details of self-sealing, protection and putty of joints from cracking.
Structural behavior of plasterboard plating
According to the principle of action, drywall is similar to reinforced concrete. The gypsum filler is solid, has high strength, load-bearing and fastening capacity. The paper casing acts as a reinforcement, preventing the mass from breaking and crumbling during linear deformations. All this makes drywall a versatile and resistant to mechanical stress material..
However, the structure of the wall cladding is not uniform, although the latter is 99% gypsum. At the joints between the sheets, the embedding does not have a reinforcing reinforcement, and therefore deformations in this area are perceived completely differently than inside the gypsum plasterboard. This leads to the appearance of cracks in the seams and to the gradual crumbling of their filler..
The main task of sealing joints is to give them the same characteristics that plasterboard has. In other words, a perfect termination makes the entire sheathing experience linear expansion as if it were a single sheet. To give the joint the properties of a slab, it must have the structure of a slab, therefore the layer of putty is reinforced with paper.
Cleaning and preparation of seams
The sheet has two types of ends. The factory ends covered with paper are packed in different shapes. They do not need any processing, because they themselves are very strong and have good adhesion..
On the other hand, trimmed ends may have a loose structure or chips and require special revision – trimming the end at an angle of 45 ° or 75 °. Trimming can be performed both during the cutting of the sheet, and after its installation on the frame. In the latter case, use a special jointing knife. Such a groove is intended for easier impregnation of the filler with a primer and gypsum milk. It is very important that when sheathing between the sheets, an indent of 1.5-2 mm is maintained.
The above is only a general approach recommended by the manufacturer. Next, we will offer a method that can be adopted by you when performing work of a high degree of responsibility with pronounced aesthetic claims..
Special end treatment
The advantage of factory pasting of the end is the presence of a small ledge, due to which the thickness of the composition applied when sealing the seam is compensated. This greatly simplifies the subsequent alignment work, especially in the inner corners. At the same time, the seam can be reinforced with full-thickness tape with guaranteed correct dressing of plaster and paper layers.
In the light of the above, the method of processing the ends to the state of the factory, applicable to work “in the field”, is of particular interest. And there is such a method: at the end of the sheet, a longitudinal cut is made with a thickness of 2 mm and a depth of 20 mm. Used for this angle grinder with a diamond disc, to which, instead of a handle, a double-sided parallel stop is fixed with a constant setting of the height and depth of cut.
After production, the cut is swept out with a brush and once, but abundantly impregnated with a general-purpose primer. After that, the slot is lubricated with busylate and glued together, forming a thinning at the edge of the sheet. For these purposes, a roller car can be adapted, made of several rows of conventional bearings, or some kind of lever press.
Materials for strengthening the seam
When you are dealing with properly prepared seams, all that remains is to choose the right materials and carry out the work in exact accordance with the technology. We considered the solution to the first problem – the seam is strengthened with paper tape. But why then there is a whole range of similar materials, and which of them deserve attention?
First of all, about fiberglass mesh: its use to strengthen any seams is not justified from any point of view. The main problem of the masking nets is the lack of normal adhesion to the gypsum mass and only two reinforcement planes corresponding to the direction of the threads. After the seal has solidified, the mesh inside the seam peels off from the mass and slips inside the putty, without interacting with it in any way.
Nonwovens behave much better. They better inherit the physical structure of cellulose, and the different direction of the fibers makes it possible to structurally strengthen the embedding, regardless of the applied load vector. Glass and carbon fiber webs and tapes differ only in much greater strength compared to paper, therefore their use is justified, for example, in the processing of seams of single-layer sheathing, with high seismic activity or active operational loads.
The paper, as you remember, looks like an optimal reinforcement in the sense that it gives the embedding a structure as close as possible to the structure of the sheet. However, branded tapes differ from regular paper in that they have longer fibers and higher penetrability. The presence of perforations or metallized inserts is also possible – the latter type is used when sealing internal fillet welds.
It should be noted that when using structural reinforcement of the entire surface, for example, with fiberglass, the material for reinforcing the joint should be the same to eliminate the heterogeneity of the leveling layer.
Before sealing the joint, make sure that it is free of dust and that the cut edges have no chipped fragments. To improve adhesion, the seam is moistened with a deep penetration primer, and the chamfers pasted over with paper must be processed more strongly.
It is recommended to use starter compounds for sealing joints. They are more ductile when hardened due to their higher porosity. The finishing putty is denser and harder than the sheet filler. The consistency of the mixture is the same as for leveling..
In general, the termination is carried out as follows:
- First, the plastic mass is forcefully pressed into the seam with transverse movements. It is necessary to achieve the complete absence of lumps and air pockets.
- After that, a thin layer of putty is applied along the entire seam, the width of which is a couple of centimeters wider than the width of the reinforcing tape.
- The tape is applied to the freshly applied putty and lightly pressed down with your fingers. In this state, it remains for several minutes for thorough moisture impregnation..
- While the mixture remains plastic, the tape must be pulled with a spatula, slightly pressing down. It is necessary to smooth out all the folds and drown the reinforcing layer as deeply as possible – it is optimal if it sits tightly against the paper.
- After removing the excess putty, the joint is covered with a thin layer 20–30 mm wide. Factory joints are overwritten flush.
Corner joints do not have much processing difference. The only exception is the development of the skill to correctly bend the metallized tape and precisely set it in the corner joint. An angled spatula usually helps with this..
Simultaneously with the sealing of the seams, the traces of the self-tapping screws are leveled with the same starting compound. After the joints have completely dried, they are treated with an abrasive mesh P-80 to remove sagging, then they are hardened with a primer and covered with a thin layer of finishing putty, improving surface adhesion and eliminating the remaining irregularities. After protective priming, such a wall is quite suitable for wallpapering; for thinner coatings, the surface should be leveled with a continuous layer.