Good afternoon, dear guests and subscribers of my channel!
In this article, I want to show the result of an experiment comparing such characteristics as water resistance between two eternal enemies: OSB and plywood.
These materials have been controversial for as long as they exist. You can talk for a long time about their pros and cons, but it is better to draw conclusions based on practice.
So:
- Plywood is a layer-by-layer glued veneer;
- OSB - pressed glued chips.
GOST
Opening GOST 3916-89, we will see that the static bending strength of plywood varies from 30 to 35 MPa, for OSB according to GOST 56309-2014 - from 15 to 30 MPa.
Stretching along the grain: Plywood 20-25 MPa, OSB 10-12 MPa.
Based on official sources, plywood is among the leaders in strength. Now, water resistance:
FSF plywood is plywood of increased water resistance, and FC is simply waterproof. Not otherwise. Many do not know this. In fact, all plywood is waterproof, which is not the case with OSB.
I prove:
OSB 1 and OSB 2 are not waterproof at all - this is given in open sources:
Now, to experiment
I took 4 cut-out squares, 2 squares common for OSB-3 roofing (18 mm.) And 2 squares of ordinary plywood of the lowest grade FC 4/4 (15 mm.)
After soaking one sample for 24 hours in regular water, I will measure the thickness and weight. Of course, I needed to take materials of the same thickness in order to compare them visually. But, since there were no identical thicknesses available, then in order to carry out the experiment fairly, in the end we will compare percentage of deformation and water absorption of samples from their original size. It will be according to the rules.
Weigh the cut out squares and measure the thickness:
After measurements, I place the samples in water for 24 hours:
A day later, I take out samples and compare them with the second dry ones:
I measure:
Weight:
Thickness:
We enter the obtained values into the plate and calculate the deviation:
So, the plywood swelled and increased in height by 1.4 mm. or 9.1%, and water absorbed 37 grams. and increased in mass by 36.7%, but looks uniformly smooth.
OSB - swelling is uneven, there is peeling of pieces of wood. Thickness increased by 2.3 mm. or 12.9%, absorbed 39 g of water. and increased in weight by 35.8%.
TOTAL
This idea of comparing materials was brought to me by a professional roofer, who explained why plywood is the best choice for roofs for bituminous (soft) shingles.
Everything is clear. Water absorption is approximately the same (~ 1% difference), but if the plywood retained its geometry, then OSB of not the worst quality went with some kind of bumps and waves.
I am not a supporter of dissembling and belittling the properties of any materials, but objectively I see that one of the best OSB (OSB-3) loses to the lowest-grade plywood FC 4/4 in water resistance, since the increase in volume and deformation is evident!
Don't believe me? Check it out for yourself, it's easy!
Thus, I think that for roofs it is better to use plywood!
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