Glued laminated timber: manufacturing technologies, secrets of building a house from glued materials

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The article analyzes and compares the design and operational features of houses made of laminated veneer lumber with natural lengths – rounded logs and profiled logs. You will learn how relevant are the typical fears and opinions about the unreliability of walls made of this material..

Glued laminated timber: features of manufacturing technology

You can often hear the reasoning: “This is bad material or technology,” and mostly we are talking about modern materials that are not older than 50 years. The object of such attacks was glued laminated timber, from which houses are supposedly subject to all conceivable and inconceivable types of deformations. Let’s try to figure out if this is really so.

Briefly about laminated veneer lumber

Glued laminated timber and beams are produced at woodworking enterprises. Logs are cut lengthwise into boards, dried, impregnated with an antiseptic and glued into finished products. Typical dimensions of laminated veneer lumber:

  • width – from 90 to 280 mm;
  • height – from 130 to 220 mm.

The width of the timber determines the thickness of the load-bearing part of the wall. Beam dimensions:

  • width – from 90 to 190 mm;
  • • height from 90 to 495 mm.

It should be noted that the production of glued products allows you to create glued beams, based on the design dimensions, a larger section (up to 600 mm) and a length of up to 12.8 m.

The difference between laminated veneer lumber and long lengths – profiled lumber and rounded logs

Everyone knows how a wooden length is prepared – cutting, delivery, sawing in profile and size, sometimes drying and impregnation. Glued structures are assembled from individual boards, they are called “lamellas”. And the first thing to remember is the strictest rejection that wood goes through at this stage of production..

Glued laminated timber: features of manufacturing technology

The second factor – only radial sawing wood goes on the lamellas – the saw passes strictly along the axis of the log, that is, the section of each individual bar or board includes annual rings, starting from the first. This means that there is no natural internal stress inside the wood, which is invariably present in long lengths of “natural workpieces” (from a 20×40 mm rail and ending with a log of any length and thickness).

What does cylindering and profiling lead to?

A living tree trunk is a perfectly calibrated “organism”. Everything in it is balanced and has its own role – bark, heartwood, sapwood, knots, etc., but if a person irresponsibly intervenes and disrupts the natural balance, problems immediately appear.

Pay attention – the sawn trunk does not warp, does not bend, remains stable until decomposition. Because all internal efforts and tensions are perfectly (naturally) balanced and balanced. If you break the structure – remove one or more layers – these forces “break out”. A 120×120 beam can be turned literally inside out, with a screw and a “rocker” at the same time – such is the strength of these stresses.

Glued laminated timber: features of manufacturing technology

In this sense, a log is more stable, because more natural layers are preserved in it. Of course, we are talking about loose lengths. If a profiled beam or a rounded log is laid “fresh” and properly fixed in the structure, then they will not be strongly driven, not counting shrinkage.

Causes of problems with houses from a bar

About “outrageous phenomena” in houses made of laminated veneer lumber did not shoot a video only lazy. Of course, not everyone will think to ask themselves the question: “What went wrong?” The overwhelming majority of problems with houses made of this material are the result of human factors, which can turn a perfectly manufactured material into a problematic structure that requires overhaul in 1-2 years..

Manufacturing defects

The most common factory defects:

  1. Wood of different moisture content. This is permissible provided that the scatter of the moisture meter readings is within 3%. Internal stresses arising from variable humidity are insignificant and are easily compensated for by the rigidity of the structure, provided that it is assembled correctly.
  2. Longitudinal cracks, cut cracks. This is a clear sign that they are trying to sell you a stale timber..
  3. Glue. This is the main “indicator” of the quality and honesty of the manufacturer. At the dawn of production, factories used relatively cheap phenol-formaldehyde glue (as in chipboard and OSB), but for the last 10 years it has been replaced by an absolutely safe, but more expensive polyisocyanate. In fact, it is a catalyst for the reaction of wood diffusion.

Glued laminated timber: features of manufacturing technology

Please note that a manufacturer who “saves” on glue will certainly “save” on high-quality lamellas by putting wood of different varieties and even species into the press.

A compliant factory will attach all required certifications without reminder. A manufacturer who has nothing to hide will allow you to inspect the workshop during the manufacture of your order, where you can make sure what kind of glue is used for your timber.

Installation defects

It’s no secret that the difference between natural lengths and glued ones is, first of all, the absence of noticeable shrinkage (up to 10% for natural ones versus 1-1.5% for glued ones). However, the owners of houses made of laminated veneer lumber show huge gaps. What could be the reason?

Three reasons for the appearance of cracks in houses made of laminated veneer lumber

1. Craftsmen often make a seemingly harmless mistake – they drive in a vertical dowel to connect the crowns flush with the top of the bar, entrusting this work to beginners or apprentices. Then shrinkage occurs, shrinkage (even by 1.5%) and the upper log or bar rests on the dowel and hangs on it – as a result, a gap appears.

Important: the dowel must be recessed at least 20 mm.

Glued laminated timber: features of manufacturing technology

2. The second and main reason is uneven conditions for identical structural elements.

If your house has a significant area (more than 150 sq. M), pay attention to the plan – it will definitely indicate the inner contour of rigidity. This is a kind of “well” from the internal walls of arbitrary geometry. This contour is a fixed support in line with the external load-bearing walls..

And now let us remember that “external walls made of glued laminated timber do not require insulation,” and the temperature and humidity drops near these walls are completely different. More precisely, the outer walls have these differences, but the inner ones do not. Accordingly, the outer walls have some mobility due to these drops and the bar of the walls tied to them begins to “walk”, and only on one side.

3. Speed. Often the performer follows the lead of the customer and assembles the “box” in record time. This race takes place in order to quickly cover the walls with a roof and begin the infinitely long meticulous process of interior decoration and furnishing of the house. The owners do not spare their time for this – finishing can take years.

Glued laminated timber: features of manufacturing technology

It is worth noting that the problem of uneven settlement is also relevant for natural long-lengths, but another one is added to it – shrinkage, which will follow the log house for the entire period of operation. This means that periodically (3-5 years) it needs to be caulked all over.

How to fix or avoid problems with laminated veneer lumber

As can be seen from the analysis, wall defects do not arise from the material itself, but from its incorrect use. Here are some tips to help you and your home:

  1. The maximum height of walls in a house made of timber, recommended by technology, is 4.5 meters. Higher walls – marketing of a company selling glued laminated timber “cubes”.
  2. Personally study the plan and highlight the external and internal load-bearing walls with different colors, calculate their indicator – area or length (with the same section). The ratio is considered normal: 80% outside – 20% inside. If the proportion changes towards the inner ones, see point 3.
  3. If you already have a plan and nothing can be changed, you need to protect the outer walls from temperature and humidity changes. The only way to protect walls from cracks and deformations, especially above 4 meters, is to insulate them with mineral wool and sheathe them.
  4. Visit the construction site more often and check the driving of dowels, talk to carpenters, ask for an explanation.
  5. “Walls don’t require finishing” is also marketing. If in your dreams you see walls made of smooth wood surfaces that are pleasant to the touch, get ready to shell out a significant amount for sanding and processing the walls..
  6. If cracks do appear, then for the outer walls there is only one “remedy” – outer sheathing, moreover, on a movable frame. It will not work to seal the gap with an inexpensive sealant from the store – the gap will be mobile and the bar will simply come off. You can use sealants for log cabins of foreign production, for example, PermaChink (USA). Those who do it professionally know how to caulk a log house.
  7. The ready-made “constructor” of the box must be mounted and unfastened at the site immediately after fitting the parts in the workshop. In no case, having purchased the material, do not postpone construction until later – this will result in free deformations. It is best to entrust the assembly to the company that produced your batch of timber.

When choosing glued laminated timber, do not chase the size and try to study the primary sources – instructions from the homeland of the technology – from the EU and the USA. This will reveal all the “secrets” of laminated veneer lumber and help to realize the capabilities of this unique material 100%.

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