Screw shrinkage expansion joints have many names: expansion jack, jack expansion joint, lift expansion joint, shrinkage jack, anchor shrinkage expansion joint. The construction of this device is very simple:
- counter plate;
- support plate;
- adjusting anchor;
- adjusting nut.
Standard sizes are:
- the area of the plates is 10×10 and 25×25 cm;
- plate height – 10–25 mm;
- bolt section – 15-30 mm.
The average cost of one expansion joint is about 300 rubles.
Before the advent of reliable metal expansion jacks, carpenters used slats, simple planks that fit under the supporting structures. As the wooden house shrank, the planks were knocked out one by one. If there was only one board, it was taken out, shuffled, reduced in thickness and reinserted. I had to use a sledgehammer and a spacer for this procedure. The carpenters, of course, adapted, but compared to the screw expansion joint, the method was unreliable..
Compensation jacks are now made of durable steel, galvanized to prevent rust. Such expansion joints can withstand significant loads, perfectly coping with the main task – compensation of shrinkage processes, prevention of cracks, in a house built of profiled, glued beams or rounded logs.
The process of using a screw expansion joint is as simple as its design: as the wooden house shrinks, the adjusting nut is tightened, the counter plate gradually lowers. Actually, the nut acts as a stopper. The log of the vertical support is specially made a little lower initially, the gap formed and is covered by the compensator. Gradually, the gap simply disappears, and the screw jack itself is completely hidden between the foundation and the support log or timber.
The screw expansion joint is placed directly on the foundation of the house, the base plate is securely screwed on. The installation process requires compliance with safety rules, it is difficult to install screw expansion joints on your own, assistants will be required. The owner of the house can regulate expansion joints during shrinkage..
The advantages of screw compensators include ease of use and reliability. Some of the disadvantages include the fact that the metal anchor expansion joint will remain forever after the gap in the tree is removed. But it’s not that bad. If the wood is of high quality, the expansion joint is made of steel, which is protected from rust – there will be no problems.
Difficulties are possible in the event that the expansion joint begins to rust inside the tree, and the beam itself or the support log were poorly processed.
Important! Compensators are installed under all supports without exception! You must not skip a single one, otherwise there is a risk that the house will subsequently burst along the line of the missed logs or beams. You should also install compensators strictly in level, making the necessary measurements.
Important! The area of the expansion joint’s metal plate should be comparable to the cut dimensions of your log or bar.
Adjustment of screw expansion joints is usually carried out about once a month, sometimes less often. The owner or an invited specialist walks around the building and, without exception, lowers all screw expansion joints by two turns of the nut. It is no longer possible, because the process of building shrinkage is gradual. More accurate calculations of the level and timing of adjustment of expansion joints can be calculated only by knowing the material for building a house, because a bar and a log give different shrinkage.