Glulam (inc. service class)

[Gus Potter]

On 10/08/2026 at 21:43, MortarThePoint said:

Thanks Gus. The main thoughts on the Staddle Stone thread are along the lines of assuming the top of the post is constrained by a connection that leave it free to rotate, would the Staddle Stone be a point of failure. So only really considering if the Staddle Stone could constrain the post vertically and horizontally, but not rotationally. I then assume that if you have a rigid body translationally constrained in two separate locations, it is then also rotationally constrained.

Hiya.

 

You are getting there. At my end my main concern is that you don't introduce lateral forces into the existing house wall. These forces would be in order of priority:

 

1/ The loggia pulling the wall outwards, (inwards load is less of an issue but still needs a quick think about)  especially as it is introduced mid floor. Your wall ties and masonry definitely won't be designed for this! Do this at your peril! 

 

2/ Adding vertical load to the lintels over the openings below that they were not designed to accommodate. 

 

3/ The loggia adding to the sideways sway forces in the plane of the external wall. These forces will be fairly small. But for due diligence always worth having a look at, just in case!

 

I can see you are getting a handle on the terminology in terms of how we describe the different forces on a connection. 

 

I'm not going to do this for you, rather, let you get your own head around this first. 

 

Your starting point is to consider the roof like a big deep beam, very stiff in resisting downwards loads and any horizontal loads, which may arise from a bit of horizontal wind load on the roof. These will be small.   Then think about all the other  loads that could be applied to that, maybe the logs will rest against the columns? These will likely dominate. I know this from designing grain stores etc. Often we don't want to indulge in excessive calculation of say wind load when we can just cut straight to the chase and identify the dominant load case and design for that. 

 

Once you have identified the loads put them on a sketch. 

 

Next we turn to the member sizing. This is pretty straight forward, a little more complex if the logs are going to rest against the columns. Often I'll clarify with a Client that they are not going to later infill part of the walls, this changes the game as it can suddenly pick up much more wind load. ! In summary though, sizing the posts is pretty straight forward.

 

The key bit is the connections. 

 

To make progress I suggest you split the forces into two different groups. The first group is the vertical and horizontal loads in each direction. That would be X, Y (Horizontal) and Z in the vertical direction. 

 

The next step is to ask yourself can I keep it stable using purely pinned connections. Just think about a single bolt as a representation of a pin, and see if that works for you. 

 

The connection between the base of the post and the straddle stone is nine times out of ten going to act like a pinned connection, thus in all likelihood your straddle stones need to be checked for what we call over turning. I'll not explain here, it's a lot to do with the passive soil resistance. I hate to say it but ask AI for an overview.  

 

In summary though, my own view is that if your loggia sinks bit or looks like it's going to fall down and gives warning of such then it would be fair to treat it as a structure of limited life span. So long as it does not compromise the structural integrity of the house, then we can be pragmatic and exercise engineering judgement. Once you investigate this a bit more then you'll be in a better position to decide what you want to do. 

 

The knee braces do work well, they are simple and cheep connections to make. With a bit of thought, if you laminate the timbers up yourself then it can be massively elegant. All you'll need is timbers off the shelf from the merchants, the right glue and some decent foundation pads at the corners with a couple of beefy fabricated steel shoes.