Glulam (inc. service class)

[MortarThePoint]

I need some beams under a loggia (veranda) with 3.1m spans. The drawing calls for 2no. 8x2 but I'm tempted to go with a Glulam instead for the following reasons:

• Normal tanalised timber will twist / cup / bow as it dries. The two timbers being joined together would help that but still
• The total length of the beam is almost 10m including its bearings (atop 150x150 oak posts) so there will need to be joins between sections if done in normal timber. I can have a single length of glulam.
• Glulam is fun to say

 

The downsides of the Glulam approach are:

• It's not treated timber
• It's more expensive: 8x2 joined together. 8x2 is around £3.80/m exVAT around my parts and I'll need to carriage bolts, timber joiners and square washers (£0.25, £0.23, £0.30 ex VAT) about every 400mm so that makes for a cost of £9.55/m exVAT. The Glulam is about £24/m + delivery.

 

As the beam is exterior but under the cover of a roof eave the glulam suppliers are saying Service Class 2 is OK.

 

I could make my own 95mm x 225mm glulam out of tanalised 4x2 at a cost of about £9/m:

   Timber: £1.60/m * 5 = £8/m

   Waterproof Urethane Glue: £0.331/m based on 0.16mm thick gives (0.16L/m2) * (4*0.045m) = 0.03L/m ,  £8.63/0.750 = £11.51/L  -> £0.331/m (Soudal Pro 45P D4 professional waterproof polyurethane wood adhesive).

   Fixings:  £0.45/m based on 1no. 5mm x 80mm every 400mm for each joint so works out as one every 100mm, 10/m and they cost £4.50/100

The eased edges would make for bumps in the beam which are a shame. Scant timber is actually more expensive (+33%) than eased edge and I don't know how available it is tanalised. Planing off the eased edge would reduce the timber to about 40mm and the glulam to 95mm x 200mm or raise the number of laminations to 6. It would likely cost a jointer blade too (£12) as well as taking a very long time. It will get painted, so I could not remove the eased edges and fill all the grooves with waterproof wood filler (120ml/m -> £1.50/m).

 

Has anyone else been down this road, either buying a premade glulam or making one themselves?

[Oz07]

5 hours ago, MortarThePoint said:

I need some beams under a loggia (veranda) with 3.1m spans. The drawing calls for 2no. 8x2 but I'm tempted to go with a Glulam instead for the following reasons:

• Normal tanalised timber will twist / cup / bow as it dries. The two timbers being joined together would help that but still
• The total length of the beam is almost 10m including its bearings (atop 150x150 oak posts) so there will need to be joins between sections if done in normal timber. I can have a single length of glulam.
• Glulam is fun to say

 

The downsides of the Glulam approach are:

• It's not treated timber
• It's more expensive: 8x2 joined together. 8x2 is around £3.80/m exVAT around my parts and I'll need to carriage bolts, timber joiners and square washers (£0.25, £0.23, £0.30 ex VAT) about every 400mm so that makes for a cost of £9.55/m exVAT. The Glulam is about £24/m + delivery.

 

As the beam is exterior but under the cover of a roof eave the glulam suppliers are saying Service Class 2 is OK.

 

I could make my own 95mm x 225mm glulam out of tanalised 4x2 at a cost of about £9/m:

   Timber: £1.60/m * 5 = £8/m

   Waterproof Urethane Glue: £0.331/m based on 0.16mm thick gives (0.16L/m2) * (4*0.045m) = 0.03L/m ,  £8.63/0.750 = £11.51/L  -> £0.331/m (Soudal Pro 45P D4 professional waterproof polyurethane wood adhesive).

   Fixings:  £0.45/m based on 1no. 5mm x 80mm every 400mm for each joint so works out as one every 100mm, 10/m and they cost £4.50/100

The eased edges would make for bumps in the beam which are a shame. Scant timber is actually more expensive (+33%) than eased edge and I don't know how available it is tanalised. Planing off the eased edge would reduce the timber to about 40mm and the glulam to 95mm x 200mm or raise the number of laminations to 6. It would likely cost a jointer blade too (£12) as well as taking a very long time. It will get painted, so I could not remove the eased edges and fill all the grooves with waterproof wood filler (120ml/m -> £1.50/m).

 

Has anyone else been down this road, either buying a premade glulam or making one themselves?

Use the 8x2

[Gus Potter]

10 hours ago, MortarThePoint said:

need some beams under a loggia (veranda) with 3.1m spans.

Is this a trick? Some say a loggia is part of the main structure or are you just being too smart. 

 

If it is part of the main structure then you also have to often transfer sideways sway resistance back in the main structure. Or have another way of resisting lateral sway. 

 

Post a dimensioned drawing and let us see what you are wanting to achieve. 

 

It looks to me like you are designing on the hoof, but don't actually understand what you are doing. 

 

Get a grip of this first and then think about your timber / Gluelam selection and the appropriate connections. Your connections are vitally important. But I suspect you have to date not given this some serious thought. Just ask yourself what is going to stop this swaying sideways. 

 

Edited Wednesday at 22:08 by Gus Potter

[MortarThePoint]

7 hours ago, Gus Potter said:

Is this a trick? Some say a loggia is part of the main structure or are you just being too smart. 

 

If it is part of the main structure then you also have to often transfer sideways sway resistance back in the main structure. Or have another way of resisting lateral sway. 

 

Post a dimensioned drawing and let us see what you are wanting to achieve. 

 

It looks to me like you are designing on the hoof, but don't actually understand what you are doing. 

 

Get a grip of this first and then think about your timber / Gluelam selection and the appropriate connections. Your connections are vitally important. But I suspect you have to date not given this some serious thought. Just ask yourself what is going to stop this swaying sideways. 

 

 

Sorry, I should have shared more context and the other thread about the loggia which you have kindly contributed to. My last query there was whether I needed ceiling level ties to constrain the main beams laterally or whether the bracketry would achieve that on its own.

 

 

 

[markc]

An alternative to Glulam especially if you are going to paint it is PSL .. think of OSB in beam form. Dense, doesn’t rot, bend or split etc.

[MortarThePoint]

20 minutes ago, markc said:

An alternative to Glulam especially if you are going to paint it is PSL .. think of OSB in beam form. Dense, doesn’t rot, bend or split etc.

 

Interesting, but I'd be a little nervous of using them externally.

[SimonD]

20 hours ago, MortarThePoint said:

either buying a premade glulam

Yes, and they're great. All ours came from https://www.bucklandtimber.co.uk/

 

They'll design and supply all junctions and fixing for you too.

[saveasteading]

I made a pergola with a Glulam equivalent. The main difference being that this was in Spain. 

So termites and heat were more the worry than wet.

After 7/8 years it's good.

 

In UK conditions I'd ve worried about the effect of prolonged dampness on the wood and the glue.

 

So my suggestion is to get treated timber, preferably choosing the lengths yourself. Now would be a good time because they might be dry.

I'd want to set them aside with air flow and a cover for a few weeks. If they distort then get them changed because they are not supposed to. The timber association TRADA says they should be kept dry but no merchants pay any attention.... I had 50 big pieces exchanged without protest.

 

Then bolt them together at 500mm cc max and perhaps add nail plates.

[MortarThePoint]

I like the idea of making my own glulam as it saves a lot of lead times and would be fun to do. The main concern would be the effects of weather (humidfity and temperature) and whether that could cause delamination. I guess if I choose the right glue, it shouldn't be much more likely to fail than an off the shelf glulam, though those probably use pressure during the glue curing and I could only use the pressure provided my screws.

[saveasteading]

1 hour ago, MortarThePoint said:

if I choose the right glue, 

That's why I suggested bolts and nail plates. Add glue if you want and the bolts will pull it tight. But even  if the glue fails completely it will perform as well.

Nailplates: I've used the wrong term. I had in kind these, called plate connectors but meant that they had spikes on both sides to join the touching faces. But these linking the tops and bottoms would work. 

I'm assuming it's out of sight!

[MortarThePoint]

37 minutes ago, saveasteading said:

That's why I suggested bolts and nail plates. Add glue if you want and the bolts will pull it tight. But even  if the glue fails completely it will perform as well.

Nailplates: I've used the wrong term. I had in kind these, called plate connectors but meant that they had spikes on both sides to join the touching faces. But these linking the tops and bottoms would work. 

I'm assuming it's out of sight!

Was hoping to leave it on show and paint it. Using screws internally to the glulam would allow three faces to have no fixings showing

[saveasteading]

52 minutes ago, MortarThePoint said:

Was hoping to leave it on show and paint it.

Isn't the attraction of glulam , other than the long spans which you don't have, that it looks pretty?

Painting and screws kind of lose that.

OK I think I'm going to let you get on with it.  But good luck.

 

 

[Russell griffiths]

I have a couple of large beams under a carport

i used a kerto beam instead of gluelam, loads cheaper. 

[Oz07]

19 minutes ago, Russell griffiths said:

I have a couple of large beams under a carport

i used a kerto beam instead of gluelam, loads cheaper. 

Did you price it up vs steel? Not sure if just went to a dear supplier but had a price years ago and steel was cheaper. Crazy. 

[saveasteading]

3 hours ago, Oz07 said:

steel was cheaper. Crazy. 

Not really. Steel is old tech and mass produced. Kerto is hitech and a smaller market...and heavy.

You might even find second hand steel.

[Gus Potter]

On 06/08/2026 at 07:06, MortarThePoint said:

Sorry, I should have shared more context and the other thread about the loggia which you have kindly contributed to. My last query there was whether I needed ceiling level ties to constrain the main beams laterally or whether the bracketry would achieve that on its own.

 

 

Hiya. 

 

The base brackets you show act as pins, they are just intended to carry vertical load only. They do have a minimal shear load capacity, but it is minimal. That (shear) is the load horizontal to the plane of the ground surface. The brackets you show are of minimal strength. 

 

To stop it moving sideways there are a number of different options. We can do a flat portal type of frame, often with knee braces. But this is going to introduce shear load into the brackets you show, they are not big enough and likely neither are the pads they rest on by the looks of things. The pads might be able to carry vertical load but not horizontal loading. 

 

Or you can fit a stiff floor and roof. These then act as a diaphragm and transfer the sideways loads back to the main house. But you have to check the main house can carry this extra load. 

 

To give you a better answer, with more explanation on how it works, need to see cross section drawings and a bit more of the house you are going to add load to if you use the diaphragm method. 

 

On 06/08/2026 at 17:21, MortarThePoint said:

I like the idea of making my own glulam as it saves a lot of lead times and would be fun to do. The main concern would be the effects of weather (humidfity and temperature) and whether that could cause delamination. I guess if I choose the right glue, it shouldn't be much more likely to fail than an off the shelf glulam, though those probably use pressure during the glue curing and I could only use the pressure provided my screws.

Ah like your idea. Quick story. When I was at uni one of my structures lecturers was into wood as a hobby. He used to buy tree trunks, cut them up into sizes in his garden, season the wood and make stuff. He did an extension with a curved vaulted ceiling in oak. To make it work he wanted to laminate the planks, turn them into a Glulam type beam We had remained in touch and once I started practising he asked me if I though I could prove this calculation wise. The answer is yes. I won't explain here but it's not too hard, if you know how to do it. 

 

This can be done DIY on a modest scale. In fact I'm deploying the same idea over a set of doors with a triangular glazed window above. I'm turning the individual 95 x 45 into a "Glulam" to carry the weight from the triangular glass above. But also I turn it into a solid timber so it better resists the wind load on the doors and glass. The cranked steels above carry the roof load. 

 

Here are the notes that go with the transom.

 

 

For you you are going to needs lots of clamps. You can used tie bolts also, messy unless you want to leave them in place. The secret is to condition your timber and make sure all glue surfaces are clean, free from oils etc, roughen them a bit and don't rush the job.  In other words cleanliness is next to godliness as is diligence. 

 

Here is a bridge near where I live.

 

 

The photo, near where I live is not that good of a laminated bridge. There are bolts going down from the top to the bottom of the beam. These transfer the shear loads between the laminations. Glue is more efficient. 

 

Hope this help inspire you to give it a go! 

 

[MortarThePoint]

Thanks Gus, nice examples of Glulams

 

9 hours ago, Gus Potter said:

The base brackets you show act as pins, they are just intended to carry vertical load only.

 

On another thread I has detailed changing to using Staddle Stones and my rough calculations there suggest a lateral force capacity at the bottom of the post of at least 80kg (without pin and resin into concrete below stone) and I'd expect much more (with pin and resin into concrete).

 

 

The main structural question I am struggling with is whether I need ceiling level timber ties back to the house structure. I'd consider the coupling between the post and the staddle stone to be free to rotate, so just providing lateral and vertical constraint but not rotary.

 

 

More discussion here:

 

 

 

[Russell griffiths]

14 hours ago, Oz07 said:

Did you price it up vs steel? Not sure if just went to a dear supplier but had a price years ago and steel was cheaper. Crazy. 

It’s visable and will be stained to match the rest of the timber, steel wasn’t even an option. 
I didn’t think it was expensive really.