Rafter Alternative Archives

There are many different brands and grades of LVL (laminated veneer lumber) on the market in Australia. Here we will compare LVL grades and demonstrate that not all LVL’s are equal. For the purpose of this topic, specific branding and products have not been mentioned. We will focus on only strength grades commonly found in Australian hardware stores.

More often or not we hear this comment on site from builders/installers; “it was the closest size i could find to the one i needed”. This often arises when we site measure jobs. Occasionally a beam installed is not what’s been specified by the project engineer. Just like framing pine has different strength grades, so does LVL. It is critical to the performance of the structure being built and the beam/lintel that’s being installed that the correct strength grade of LVL beam is being used; ‘All LVL’s are not equal’.

Knowing LVL Numbers & Grades.

LVL strength grading is usually always in the product name; ‘LVL13 or E13′ would commonly be heard. Both of these names directly relate back to the Modulus of Elasticity. The Modulus of Elasticity or ‘MOE’ is a measure of stiffness of an elastic material. It is the strength grade that tells us how much the material will bend/deflect under specific loading applications. In basic, the higher the number in the product name, the stiffer it is and will deflect less under load. LVL grades commonly seen in Australia range from E10 found in framing studs through to E19 found in LVL structural beams.

What makes one LVL stronger than another?

Visually the majority of LVL’s on the market all look the same. But what makes one LVL stronger than another; is the timber species used and the thickness of laminate veneers. Many producers will use a mixture of soft and hardwood veneers to gain a better MOE value. This also directly effects the sale price of the different products.

Lets Compare LVL Grades.

Below is a simple comparison table using some of the strength grades on the market. The table compares each LVL strength grade as a lintel typically found over a 2400 wide sliding door/window. As shown, the higher the LVL grade, the better it performs and minimises the deflection in that lintel. What is deflection you ask? Deflection is the measurement past Horizontal zero. (see Diagram 1)

Deflection is a critical value to consider when designing any beam or lintel. There will always be deflection in any structural member but there are things to consider which can limit this value.

GRADE	ELASTICITY (mpa)	STRENGTH GROUP	JOINT GROUP	DEFLECTION	STRESS RATIO
LVL13	13200	SD5	JD4	8.1mm	81.2%
LVL13.2	13200	SD6	JD3	8.1mm	81.2%
LVL14	14000	SD6	JD4	7.7mm	76.5%
LVL15	15300	SD6	JD3	7.5mm	74.9%
LVL19	19500	SD3	JD2	5.5mm	55.2%

Worked Example 1: Upper lintel spanning 2450mm (typical sliding door size)

Summary-

As the heading states; Not all LVL’s are equal and will not perform the same. So when substituting LVL members, consider its strength grading and not just its physical sectional size. If you are unsure, seek further clarification on a substitution LVL for your next job, talk to your project engineers or CONTACT US

Links:

Learn More about ‘Timber Joint Groups’

Learn more about ‘Timber Strength Groups’

FG rafters are a great time saving rafter alternative to LVL & I joist rafters often nominated by engineers & building designers. The benefits for the builder far outweigh the other alternatives.

Developed in 2020 by The Truss Joint with MiTEK engineers the FG Rafter was born when the building industry suffered sever timber shortages. LVL and other engineered timber products were near impossible to acquire and build times blew out due to wait times. We developed the FG Rafter to keep our clients & builders moving during hard times.

Since their inception into our product line we have provided FG Rafters into many applications. Most commonly used in residential builds the FG Rafters also perform well in commercial applications. Manufactured on already existing machinery, most truss manufacturers across Australia can readily produce this item and provide the market.

Builder feedback on FG Rafters has been very positive on all jobs we supplied. Being versatile in design they can accompany eave overhangs, box gutter ends and the open web style allows for any HVAC items required to be hidden. All of these items are seen as huge time savers for the builder on site as they are readily already manufactured into the rafter.

FG Rafter Benefits:

Ducting & Electrical services can be run between truss chords.
No drilling or Noting is required for electrical or support points.
Larger, better performing clear spans can be achieved.
Very lightweight and easy to handle.
Rafters are manufacture pre-cambered to minimise deflection your would otherwise face with LVL & I Joist products.
Special end details are achievable to suit Bog gutters and a variety of support scenarios.
Custom built to suit individual jobs & loading requirements.
No onsite cutting is required.
Exposed eave overhang tails can be manufactured into the Rafters.

Below are some basic design span charts using residential loads, rafter spacing and achievable spans.