Glulam Beam - Checking Problem

[rScotty]

It appears that is what the engineer will require. Running long lag/timber bolts through the bottom to bring that bottom glulam back to where it was and prevent any future issues. It did NOT delaminate (which is a different problem all together) but the bottom board was initially glued into place and it checked so it will be mechanically connected with the lags/screws.

Before you sign off on it, it may be worth keeping your options open. As I look at those photos again there seem to be separations beginning between other layers in addition to the large one. It may just be an artifact of the photograph - but you may want to take another look. If the beam was laminated too wet it is hard to see how that is going to improve with lag bolting.

Maybe it is acceptable to their engineer. My own experience with glulams is limited to one project. If it were mine I'd probably accept an opinion from a licensed professional engineer's as long as it included guarantees into the future.
rScotty

 

[Iftisam Mulani]

I had some glulam beams installed on my new house build. I am in Arizona so it was hot & dry and the beams were installed in less than 1 week after being delivered. The roof was put on and now I am noticing some checking in that glulam beam. I was told that checking is normal, especially in a hot climate but I feel uneasy about it so I contacted the glulam manufacturer and they are looking into it.

Can a glulam beam be fixed on site/installed? I've seen some online photos of them using epoxy and lag bolts to shore up the beam.
On mine, it's the bottom board that has checking in it. I know that board is under tension since it is the bottom board.

Any help would be appreciated...

you're correct that the bottom board of a glulam beam is typically under tension. However, the glulam's overall structural design takes this into account. If the manufacturer or an engineer determines that the checking is a concern, they will advise on the appropriate steps to take.

To minimize the development of checking in the future, you can consider applying a protective finish or coating to the glulam beams. This can help reduce moisture absorption and minimize the expansion and contraction that contribute to checking.

Regardless of the outcome of the manufacturer's assessment, it's a good practice to periodically inspect your glulam beams for any changes or signs of deterioration. Early detection of any issues can help prevent further complications.

 

[ponytug]

It appears that is what the engineer will require. Running long lag/timber bolts through the bottom to bring that bottom glulam back to where it was and prevent any future issues. It did NOT delaminate (which is a different problem all together) but the bottom board was initially glued into place and it checked so it will be mechanically connected with the lags/screws.

If it were me, I might enquire about injecting epoxy into the crevices before installing the lag bolts. Belt and suspenders and all that.

All the best,

Peter

 

[Pettrix]

 

[yooperdave]

Did you get a balanced lamination - tension lams on both top & bottom?
Otherwise did you make sure the beam was not installed upside down?
Upside down has half the bending capacity - unlike LVL and PSL.
Assuming your beams are not yet fully loaded.
I would not accept the beam as installed.
You could add steel side plates and long vertical lag screws after shoring to get the load off the beam- but why for brand new?

Good Luck

I used to be a glu lam structural engineer back in the 1980's.

Yooer Dave

 

[Pettrix]

Did you get a balanced lamination - tension lams on both top & bottom?
Otherwise did you make sure the beam was not installed upside down?
Upside down has half the bending capacity - unlike LVL and PSL.
Assuming your beams are not yet fully loaded.
I would not accept the beam as installed.
You could add steel side plates and long vertical lag screws after shoring to get the load off the beam- but why for brand new?

Good Luck

I used to be a glu lam structural engineer back in the 1980's.

Yooer Dave

The top of the beam was marked "TOP" in black lettering and they were installed the correct side facing up.

As mentioned, since the roof is installed, I cannot simply remove the beams without demolition of the roof. A cost of $80k + to do so.

My only option is to repair it.

Glulam engineer stated that he believes the other 2 beams are okay and structurally fine, just some checking due to dry hot air. The one beam will be repaired and I should have the details on that this week. Initially, it appears long 10" threaded timber screws from the bottom to shore up the bottom board, probably spaced 12" staggered. He also stated that if the other 2 beams were structurally compromised he would recommend fixing those also as the company doesn't want any issues should those beams fail. They always error on the side of caution and will do repairs to avoid possible failure issues later on.

 

[yooperdave]

The top of the beam was marked "TOP" in black lettering and they were installed the correct side facing up.

As mentioned, since the roof is installed, I cannot simply remove the beams without demolition of the roof. A cost of $80k + to do so.

My only option is to repair it.

Glulam engineer stated that he believes the other 2 beams are okay and structurally fine, just some checking due to dry hot air. The one beam will be repaired and I should have the details on that this week. Initially, it appears long 10" threaded timber screws from the bottom to shore up the bottom board, probably spaced 12" staggered. He also stated that if the other 2 beams were structurally compromised he would recommend fixing those also as the company doesn't want any issues should those beams fail. They always error on the side of caution and will do repairs to avoid possible failure issues later on.

Keep a close eye on the deflection. The beams should be shored with a camber up prior to reinforcing. Lag screws need to extend well beyond the neutral axis of the beam. Try not to compromise the tension lams or they will crack as well. The beams should have had a low moisture content to begin with. I am not so sure that they 'dried out'.

 

[BigGG]

Did you get a balanced lamination - tension lams on both top & bottom?
Otherwise did you make sure the beam was not installed upside down?
Upside down has half the bending capacity - unlike LVL and PSL.
Assuming your beams are not yet fully loaded.
I would not accept the beam as installed.
You could add steel side plates and long vertical lag screws after shoring to get the load off the beam- but why for brand new?

Good Luck

I used to be a glu lam structural engineer back in the 1980's.

Yooer Dave

Can you elaborate? Are some lams pre-tensioned or . . .? I always thought these were just glued and clamped together.

 

[Pettrix]

Keep a close eye on the deflection. The beams should be shored with a camber up prior to reinforcing. Lag screws need to extend well beyond the neutral axis of the beam. Try not to compromise the tension lams or they will crack as well. The beams should have had a low moisture content to begin with. I am not so sure that they 'dried out'.

I will do. I believe he wants to use these Simpson Timber Screws. 2,000 lbf of tension and 1,400 lbf of shear strength. Initial install sounds like 12" oc staggered but I don't have the detail yet

Here are some pics of the 4x6 top plates. It was solid when bought/delivered and checked within a few days after being installed. This is very common for lumber out here in Arizona.

 

[yooperdave]

Can you elaborate? Are some lams pre-tensioned or . . .? I always thought these were just glued and clamped together.

Nothing is pre-tensioned. Glued and clamped as noted. Sometimes the glue is not applied as hoped and delamination can occur.

 

[BigGG]

Nothing is pre-tensioned. Glued and clamped as noted. Sometimes the glue is not applied as hoped and delamination can occur.

What causes a beam to have a preferred top orientation?

 

[Pettrix]

What causes a beam to have a preferred top orientation?

I believe it has something to do with some designed positive camber in the beam. So when the beam is installed, it goes from a positive camber to neutral once the loads are applied.

 

[yooperdave]

What causes a beam to have a preferred top orientation?

The tension lams are the best material and put on the bottom for maximum strength. As noted earlier, the capacity of the beam is cut in half if installed upside down, as the compression lams do not have the strength. The use of LVL and PSL eliminates this issue.

 

[Pettrix]

So with the Simpson fully threaded timber screw with 2,000 lbf of tension and 1,400 lbf of shear strength per screw. That screw would be stronger than the original wood and bond glue, wouldn't it?

I am wondering if it would be a good idea to just run some of those screws in the other 2 beams as added security?

 

[bnold]

So with the Simpson fully threaded timber screw with 2,000 lbf of tension and 1,400 lbf of shear strength per screw. That screw would be stronger than the original wood and bond glue, wouldn't it?

I doubt it. The tension strength is just the ‘squeeze’ of the boards together, not really adding anything to the strength in the direction the beam gets it’s strength from. The shear strength of the screw could add to the resistance of the boards passing by one another as the load is applied, but I doubt it is anything significant compared to the full glue-up of the assembly.


I’m surprised they don’t recommend injecting glue or epoxy in the check prior to driving the screws. That would be my fix.

 

[yooperdave]

So with the Simpson fully threaded timber screw with 2,000 lbf of tension and 1,400 lbf of shear strength per screw. That screw would be stronger than the original wood and bond glue, wouldn't it?

I am wondering if it would be a good idea to just run some of those screws in the other 2 beams as added security?

The glue transfers horizontal shear between the laminations so the member acts compositely. The new screw needs to now transfer the shear (if no epoxy). The shear can be calculated and compared to the allowable shear capacity of the screw.

And yes, the beam should be shot up with epoxy after the beam has been shored with a camber up. The epoxy will restore much of the integrity if performed properly. The screws will draw up the lams and close the cracks. The epoxy and screws will both transfer shear.

 

[ponytug]

So with the Simpson fully threaded timber screw with 2,000 lbf of tension and 1,400 lbf of shear strength per screw. That screw would be stronger than the original wood and bond glue, wouldn't it?

I am wondering if it would be a good idea to just run some of those screws in the other 2 beams as added security?

I would not do it as a "just in case". Screws cut the fibers in the wood and that is damage. It can also provide a point or checking and cracking to originate from.

If you have checking concerns for the other beams, I would raise those concerns with beam manufacturer, and see what they recommend.

All the best,

Peter

 

[rScotty]

So with the Simpson fully threaded timber screw with 2,000 lbf of tension and 1,400 lbf of shear strength per screw. That screw would be stronger than the original wood and bond glue, wouldn't it?

I am wondering if it would be a good idea to just run some of those screws in the other 2 beams as added security?

A timber screw with a fully threaded shank as you show can only provide a clamping force to the area directly under the head - and that force is limited becase it cannot exceed the the compressive stress of the fibers it bears on. The force is farther reduced by the angle of head.
Think about it: a fully threaded shank CANNOT pull two pieces of wood together, and the head angle only hurts that effort.
That type of screw is a poor choice for the purpose.
I am afraid that you need to find some competent engineering help.
rScotty

 

[Pettrix]

A timber screw with a fully threaded shank as you show can only provide a clamping force to the area directly under the head - and that force is limited becase it cannot exceed the the compressive stress of the fibers it bears on. The force is farther reduced by the angle of head.
Think about it: a fully threaded shank CANNOT pull two pieces of wood together, and the head angle only hurts that effort.
That type of screw is a poor choice for the purpose.
I am afraid that you need to find some competent engineering help.
rScotty

I am going by with what the glulam engineer is advising. Should I try and find another engineer to see what they recommend?

I am not sure why would the glulam engineer design something that would fail. The liability would be high.

 

[yooperdave]

I am going by with what the glulam engineer is advising. Should I try and find another engineer to see what they recommend?

View attachment 814731


View attachment 814732

Do NOT toenail. Predrill lead holes from the bottom and screw-up like a good politician. The epoxy should transfer shear. The screws will hold it together while the epoxy cures. Toe nails may not draw up and close the crack as intended.

Yooper Dave