Since a glulam beam is intended to bear a certain load, I personally could never consider making it myself. Just imagine if your life's work(!) gives way because you used the wrong type of glue that didn't dry under the right pressure on a too wet (or dry) wood surface...
Did this when we remodeled the sunroom at the previous house, a neighbor who was a carpenter and had access to woodworking machines helped me. First, we planed all the pieces, losing at least 5mm of material, then glued them with polyurethane glue (waterproof), and used about 30 clamps on 4 meters.
This was a beam that was to be placed above a sliding door section. It worked well. It was fun. However, I would never have done this on a "real" house, the sunroom is another matter.
Actually, it's doubtful if it was worthwhile, I recall the materials cost about 600 SEK and the glue alone cost 150 SEK.
The homemade beam can probably never be as good as the factory-made one, among other things, I think they finger-plane the sides so the glue surface is much larger, and they can obviously press the parts together much better in a factory.
This was a beam that was to be placed above a sliding door section. It worked well. It was fun. However, I would never have done this on a "real" house, the sunroom is another matter.
Actually, it's doubtful if it was worthwhile, I recall the materials cost about 600 SEK and the glue alone cost 150 SEK.
The homemade beam can probably never be as good as the factory-made one, among other things, I think they finger-plane the sides so the glue surface is much larger, and they can obviously press the parts together much better in a factory.
In industrial manufacturing of glulam beams, they start by "finger jointing" the timber, essentially creating an infinitely long plank. The finger joint itself is stronger than the wood surrounding it. The infinite plank is then cut to the correct length before being glued and pressed. It is not the glue joint that breaks when the load becomes too high; it is the wood that splinters.
If you're a bit unsure about the glue's ability and are short on clamps during self-manufacturing, you can also screw/nail the beam
An alternative to Glulam beams is to fell a giant tree and have it sawn into a substantial beam. A relative felled two sizeable pines, each providing a 9m long 250x250 beam, which was knot-free on the surface 8) It also yielded a number of knot-free boards "outside" during sawing. However, it requires some machinery to handle such trees
If you're a bit unsure about the glue's ability and are short on clamps during self-manufacturing, you can also screw/nail the beam
An alternative to Glulam beams is to fell a giant tree and have it sawn into a substantial beam. A relative felled two sizeable pines, each providing a 9m long 250x250 beam, which was knot-free on the surface 8) It also yielded a number of knot-free boards "outside" during sawing. However, it requires some machinery to handle such trees
How do you know what dimension to choose for your homemade glulam beam? If the designer specifies a dimension and you create your own beam that likely doesn't have the same durability, how do you know if you've allowed sufficient margins? It's something you shouldn't skimp on—the construction. Follow the designer's instructions meticulously. If you want to change something, consult the designer for advice first.
Best regards,
David
Best regards,
David
Part of the question is how to manufacture a beam in a smarter way.
A conventional glulam beam is quite straightforwardly constructed: The same material thickness all the way through.
Sirbo had his cousin the tinsmith, who built a beam using plywood (instead of a lot of wood), which is somewhat smarter.
So, strength specialists:
if you build a beam with, for example, 2 pcs of 45x95 with 12x360 plywood in between, and glue and nail well,
Schematic sketch:
|XXXX|
| |
| |
| |
|XXXX|
what does this correspond to in terms of strength for a glulam beam?
Anyone understood? ???
//KoW
A conventional glulam beam is quite straightforwardly constructed: The same material thickness all the way through.
Sirbo had his cousin the tinsmith, who built a beam using plywood (instead of a lot of wood), which is somewhat smarter.
So, strength specialists:
if you build a beam with, for example, 2 pcs of 45x95 with 12x360 plywood in between, and glue and nail well,
Schematic sketch:
|XXXX|
| |
| |
| |
|XXXX|
what does this correspond to in terms of strength for a glulam beam?
Anyone understood? ???
//KoW
I dug up my old high school knowledge and calculated your beam example. When you say "structurally equivalent," you need to break it down into two different properties of the beam:
1: The rigidity, i.e., how much deflection the beam will have.
2: The bending resistance, i.e., the load the beam can withstand before it breaks.
According to my calculations, your box beam 95x360 is equivalent to a glulam beam 95x300 in terms of rigidity and 95x238 in terms of bending resistance. I have only calculated the studs. I have disregarded the plywood's contribution.
Does anyone come to a different conclusion?
Now, this is a simplified and theoretical calculation. I suspect that if the box beam were loaded until it broke, it would fail in a completely different way than the solid one.
1: The rigidity, i.e., how much deflection the beam will have.
2: The bending resistance, i.e., the load the beam can withstand before it breaks.
According to my calculations, your box beam 95x360 is equivalent to a glulam beam 95x300 in terms of rigidity and 95x238 in terms of bending resistance. I have only calculated the studs. I have disregarded the plywood's contribution.
Does anyone come to a different conclusion?
Now, this is a simplified and theoretical calculation. I suspect that if the box beam were loaded until it broke, it would fail in a completely different way than the solid one.
I can add before someone else does: there is a strong reason to use massive beams instead of box beams and that is fire safety. A box beam burns and loses its strength much faster than a massive beam. I have seen information that glue-laminated timber is even more fire-safe than steel beams.
KnockOnWood said:
You are talking about something called "Lättbalk" in Swedish or "Fabricated Wood" in US English.
When I was working in the USA, they test this "timber" to about 1,200 kg / meter or scrap the production batch.
But they don't make this class 360 mm high but something closer to 2 x 45x70 with one or two plywood sheets at 12 mm between at a height of about 200-240 mm.
It's also possible to brace with three layers
top rule 2" x 3"
plywood + chipboard + plywood
bottom rule 2" x 3"
though now we're talking extreme strengths and lots of automatically fed polyurethane glue and automatic mitre saws with a production of 600 meters per hour
It would be fun if someone could link to Swedish values, measurements, and models.:x
PS. // note that the plywood is recessed into grooves in each 2x3 " rule and not overlayed since an overlayed would likely give poorer torsional strength and longitudinal shear of the beam as a whole.
The fire risk definitely increases, as noted above, and yes, glue-laminated timber is better than steel because steel's properties change already at heating, and the hardening permanently changes to a softer material.
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Homemade load-bearing structures work well for building parts whose function is not directly tied to the load-bearing capacity of vital parts. The example with the panel door was a good one.
In a composite beam, the load transfers to shear stresses in the interface between the different materials. This means very high demands on the adhesion between plywood and wood in the homemade box beam.
In the factory, they have very special types of glue, some are two-component, but there are also types that cure with heat or UV light.
It's probably quite difficult to achieve really good results without a proper press. Additionally, the beams you buy are rated and approved, which means you can safely order what the designer has specified.
In a composite beam, the load transfers to shear stresses in the interface between the different materials. This means very high demands on the adhesion between plywood and wood in the homemade box beam.
In the factory, they have very special types of glue, some are two-component, but there are also types that cure with heat or UV light.
It's probably quite difficult to achieve really good results without a proper press. Additionally, the beams you buy are rated and approved, which means you can safely order what the designer has specified.
Oh, this must be a forum record in thread revival. I can at least tell you that the glulam beam I was thinking about when I started the thread, and which Svedalahem, Sville, and David strongly advised me not to build, was built anyway. It was part of an ice yacht. I have also built several light beams from studs and plywood, which I have used in house constructions.
Yes, that was a nice thread lift...
Saturnus makes their own glulam beams.
http://www.byggahus.se/forum/byggmaterial-byggteknik/94599-mer-limtrae.html
There might be a little more written about it in another thread, search with the forum's search on glulam beam* and user saturnus...
Saturnus makes their own glulam beams.
http://www.byggahus.se/forum/byggmaterial-byggteknik/94599-mer-limtrae.html
There might be a little more written about it in another thread, search with the forum's search on glulam beam* and user saturnus...