2-Ply Glulam Beams - Nails?

[Mulberry View]

I've got to build a number of 2-Ply Glulam Beams for my First Floor Posi design. The supplier has given me instructions like this...

 

 

I've never done this, so need a bit of further guidance. Does this denote one nail at each location? Can these be hand nailed?

 

I'm a self-taught DIY'er, so have always screwed everything! Using nails is new to me. LOL. What's the benefit of nailing over screwing?

[BotusBuild]

2 hours ago, Mulberry View said:

Does this denote one nail at each location? Can these be hand nailed?

Yes, and Yes

2 hours ago, Mulberry View said:

What's the benefit of nailing over screwing?

Quicker - especially if you have or hire a functioning nailgun

[Mulberry View]

2 minutes ago, BotusBuild said:

Yes, and Yes

Quicker - especially if you have or hire a functioning nailgun

 

So could these be screwed instead if time weren't the critical factor?

 

I have a 3-ply beam and the fixing pattern for that is 12x180 hex bolts, which I'm far more comfortable with.

[BotusBuild]

I'm no expert, but using screws instead of nails should be OK, IMHO (waits to be torn a new one by an expert)

[Mike]

34 minutes ago, Mulberry View said:

So could these be screwed instead if time weren't the critical factor?

No, not in a structural element unless the designer says so. Screws are primarily intended to resist pulling out, nails are primarily intended to resist shear (sideways) forces. Stick to the specified nails.

 

[Mulberry View]

12 minutes ago, Mike said:

No, not in a structural element unless the designer says so. Screws are primarily intended to resist pulling out, nails are primarily intended to resist shear (sideways) forces. Stick to the specified nails.

 

 

OK, will do. But can these be satisfactorily hand-nailed? What sort of nails should I buy? Like these...?

 

https://tradefixdirect.com/p/stainless-steel-a2-304-annular-ring-nails-75-x-3-35mm/?gad_source=1&gclid=Cj0KCQiAzoeuBhDqARIsAMdH14F9e1wwi5PKmsk9mPj2vmeDJ4j4oaoRREkshvRn3p26U9MeNdI-V_8aAkteEALw_wcB

[Mike]

29 minutes ago, Mulberry View said:

What sort of nails should I buy?

Regular smooth 3.35 x 75 nails as specified, such as these:

 

https://www.fixingsfastenersscrews.co.uk/details/p3380228_21380657.aspx

[BotusBuild]

1 hour ago, Mike said:

No, not in a structural element unless the designer says so. Screws are primarily intended to resist pulling out, nails are primarily intended to resist shear (sideways) forces.

Told you an expert would be along soon 🙂

[SteamyTea]

Nails, screws and bolts all work differently.

 

Hand nailing can be a bit of a pain if access is limited.

[Mulberry View]

1 hour ago, SteamyTea said:

Nails, screws and bolts all work differently.

 

Hand nailing can be a bit of a pain if access is limited.

 

I had thought I'd be building these on the floor, but the weight will be my limiting factor.

[Conor]

I remember the day I had to put in ~500 30mm nails through joist brackets with a hammer and limited access. Was a good year ago. My arm is still sore and I get flashbacks.

[Gus Potter]

7 hours ago, Mulberry View said:

I've got to build a number of 2-Ply Glulam Beams for my First Floor Posi design. The supplier has given me instructions like this...

Good question.

 

Hope some of it helps someone, especially those designing their own TF in principle and some of the things you need to think about..I make some general comments.

 

The two diagrams you posted look as they do.. but odd in some ways. Starting from the top.

 

1/ The grade of Glulam 28c.. your TF supplier? They I assume will have priced for this on how they operate / cost / lead times but a 28c often carries a significant price premium in one way or another compared with a 24c or a 24h grade which is less strong but is made from more readily available timber. I would ask the question.. is it cheaper to use a 3 ply in 24c or 24h and can it be fitted in?

 

Ok.. you may ask what is the difference between the suffix c & h? A Gluam beam is built up from layers of timber glued together. When a Glulam beam is subject to bending forces only (usually from a floor) and rests directly on say on a wall head we can make the beam out of stronger timber on the top and bottom and put weaker timber in the middle. This means we combine different strengths (grades) of timber hence the c = combined so more economic.

 

The h grade means that we use the same strength (grade) of timber for all the beam laminations so it is homogeneous = h

 

Now in some cases, say for a beam resting on a wall this is ok.. but it is often NOT ok when we want to connect a glulam to something else using say Simpson Strong_Tie connections or a steel beam unless you design on the weakest bit of wood! and if you do that then why pay for a higher grade of beam when you could make it thicker say.

 

Big heads up.. if you have a separate SE make sure they know what the TF designer is assuming!

 

Nail spacing horizontally (600mm) . This looks a bit far apart to my eye. I would go for 250 - 300mm centres. Now this may seem a bit trivial to the naked eye but it matters when you do your design checks. A closer nail spacing means that you can treat the two Glulams as acting together (compositely) so you get more bang for your buck in terms of performance. The spacing shown looks odd. Ask the question.. basically has the detailer not implemented the SE's design?

 

The nails are all shown with the heads on the same side. This is not good practice. Also the nail length is indicated as 75mm. 75mm less 45 mm only gives you a point penetration into the Glulam behind of 30mm which goes against the principle of nail design. I would specify a 90mm long ring shank nail for this. Ask why they are all from the same side, not opposing and appear to short.

 

The distance of the nail down and up from the top and bottom of the Glulam. If we are using solid timbers nailed together then we often stagger the nails above and below the horizontal centreline of the beam by about 25-35% of the depth of the beam, it varies depending on beam depth so this figure is representative. We do this as solid timbers tend to "cup"over time. In other words the middle bows in or out from the centreline. You can often see this in old solid timber joists where the sides are bowing.. cupping. Cupping happens when the older wood shrinks differently from the younger wood.

 

Now Glulam beams are not supposed to be too succeptible to this type of cupping behaviour when surrounded by air of the same moisture content on both sides. But if not they will cup to some extent. If you nail the beams together in the way shown you could cause them to cup and split the lamination.. now you have a problem! Suggest you go back and ask the TF designer if they have thought about this and can confirm that for your application all is ok given the 30mm nail point penetration which raises an eyebrow.

 

Last but not least.. you are going to be fixing a ceiling and floor to the top and bottom of the Glulams possibly. The floor in particular serves to brace the tops of the joists to stop them twisting sideways and if you stop this you get a good stiff floor. Now the flooring nails will likely compromise the nails you show in terms of code compliance. That is why I sugest earlier that the nails are staggered above and below the horizontal centreline, it keeps them away from the flooring / noggings / ceiling nails. Suggest you go back to TF detailer and query. Check the specification and point penetration required by the flooring manufacture and you may find the TF and flooring spec clash.

 

For all. At the end of the day once you get your head round the principles of how timber works then it's a great material to build a house from. The above is a bit tecky but if you think about it much is common sense!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Mulberry View]

55 minutes ago, Gus Potter said:

Good question.

 

Hope some of it helps someone, especially those designing their own TF in principle and some of the things you need to think about..I make some general comments.

 

The two diagrams you posted look as they do.. but odd in some ways. Starting from the top.

 

1/ The grade of Glulam 28c.. your TF supplier? They I assume will have priced for this on how they operate / cost / lead times but a 28c often carries a significant price premium in one way or another compared with a 24c or a 24h grade which is less strong but is made from more readily available timber. I would ask the question.. is it cheaper to use a 3 ply in 24c or 24h and can it be fitted in?

 

Ok.. you may ask what is the difference between the suffix c & h? A Gluam beam is built up from layers of timber glued together. When a Glulam beam is subject to bending forces only (usually from a floor) and rests directly on say on a wall head we can make the beam out of stronger timber on the top and bottom and put weaker timber in the middle. This means we combine different strengths (grades) of timber hence the c = combined so more economic.

 

The h grade means that we use the same strength (grade) of timber for all the beam laminations so it is homogeneous = h

 

Now in some cases, say for a beam resting on a wall this is ok.. but it is often NOT ok when we want to connect a glulam to something else using say Simpson Strong_Tie connections or a steel beam unless you design on the weakest bit of wood! and if you do that then why pay for a higher grade of beam when you could make it thicker say.

 

Big heads up.. if you have a separate SE make sure they know what the TF designer is assuming!

 

Nail spacing horizontally (600mm) . This looks a bit far apart to my eye. I would go for 250 - 300mm centres. Now this may seem a bit trivial to the naked eye but it matters when you do your design checks. A closer nail spacing means that you can treat the two Glulams as acting together (compositely) so you get more bang for your buck in terms of performance. The spacing shown looks odd. Ask the question.. basically has the detailer not implemented the SE's design?

 

The nails are all shown with the heads on the same side. This is not good practice. Also the nail length is indicated as 75mm. 75mm less 45 mm only gives you a point penetration into the Glulam behind of 30mm which goes against the principle of nail design. I would specify a 90mm long ring shank nail for this. Ask why they are all from the same side, not opposing and appear to short.

 

The distance of the nail down and up from the top and bottom of the Glulam. If we are using solid timbers nailed together then we often stagger the nails above and below the horizontal centreline of the beam by about 25-35% of the depth of the beam, it varies depending on beam depth so this figure is representative. We do this as solid timbers tend to "cup"over time. In other words the middle bows in or out from the centreline. You can often see this in old solid timber joists where the sides are bowing.. cupping. Cupping happens when the older wood shrinks differently from the younger wood.

 

Now Glulam beams are not supposed to be too succeptible to this type of cupping behaviour when surrounded by air of the same moisture content on both sides. But if not they will cup to some extent. If you nail the beams together in the way shown you could cause them to cup and split the lamination.. now you have a problem! Suggest you go back and ask the TF designer if they have thought about this and can confirm that for your application all is ok given the 30mm nail point penetration which raises an eyebrow.

 

Last but not least.. you are going to be fixing a ceiling and floor to the top and bottom of the Glulams possibly. The floor in particular serves to brace the tops of the joists to stop them twisting sideways and if you stop this you get a good stiff floor. Now the flooring nails will likely compromise the nails you show in terms of code compliance. That is why I sugest earlier that the nails are staggered above and below the horizontal centreline, it keeps them away from the flooring / noggings / ceiling nails. Suggest you go back to TF detailer and query. Check the specification and point penetration required by the flooring manufacture and you may find the TF and flooring spec clash.

 

For all. At the end of the day once you get your head round the principles of how timber works then it's a great material to build a house from. The above is a bit tecky but if you think about it much is common sense!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

That's one heck of a reply, thanks @Gus Potter

 

I have read over it, but I need to absorb what you're saying in more detail. To be clear though, this is a Posi solution only, my house is built from Nudura ICFs!

 

As for the spec, my Posis were supplied by Pasquill. They have tolerated my relentless questions and constant push to improve the design. It's only a small First Floor area (around 80m2) but I wanted no discernible bounce, so they have worked to a deflection limit if 10mm, which my scheme comfortably exceeds and within that is the scope for us to install a large bath upstairs (worst case 225kg bath and 625kg for water and occupants - we're not likely to go *that* big).

 

The overall scheme spec might be why the Glulams have been spec'd using a higher grade material, if I have read your comments correctly.

 

With all that said, I'm new to this aspect of our build and keen to do the very best I can, so all words of advice are gratefully received.

[Canski]

On 07/02/2024 at 21:00, Conor said:

I remember the day I had to put in ~500 30mm nails through joist brackets with a hammer and limited access. Was a good year ago. My arm is still sore and I get flashbacks.

I remember the day when I instructed my labourer to fill in all the holes in the joist hangers with twist nails. I told him that if he ran out there was another bag of nails in the shed. He got the wrong bag and despite nailing a hundred or so twist nails continued with galvanised roofing nails. 
He will remember the day he had to pull them all out again.