Traditional Oak Framing or Modern Fixings

[MortarThePoint]

I'm making a simple porch frame to go between two walls and I am pondering between a bridle cut and a simpler to make bolt held option (M12 x 250 Stainless). The two options are at the bottom of this post (but at the top of the porch post :-). Vertical posts are 145x145 and horizontal beam is 95x195. Although it's more effort, I am currently leaning towards the bridle cut. It would prevent any light passing though a narrow gap that could open up through shrinkage. It's much more work to make though and the finished result will look identical bar any gaps. Silly?

 

 

Edited September 22 by MortarThePoint

[MortarThePoint]

I could drill and peg at the join to fill the gap, but I'd have to be very careful not to blow through with the drill and there would still be a small unplugged gap left

[garrymartin]

If it's a pre-existing structure, will you have enough clearance to get the bridle cut post in place?

[MortarThePoint]

1 minute ago, garrymartin said:

If it's a pre-existing structure, will you have enough clearance to get the bridle cut post in place?

 

Good question. There are posts at each end of the beam which will be fixed lower down to the wall. The bridle cuts at the end would have to be like this I expect

 

 

[MortarThePoint]

A concern with the bridle cut that isn't an issue with the modern fixing approach is he possibility of the post splitting due to it shrinking more than the beam

[garrymartin]

Ah, you're making the entire frame, not trying to put vertical pieces into something that is already there. I misunderstood. In that case, definitely the bridle cut if your woodworking skills are up to it.

[ToughButterCup]

22 hours ago, MortarThePoint said:

.... It's much more work to make though and the finished result will look identical bar any gaps. Silly

 

No: the opposite.

 

Making it parallels learning ( for which read  the 'errors' ) involved. That learning builds over time. And thus confidence. 

But most of all quiet satisfaction. And deep pleasure if only we ( I ?) allow ourselves to enjoy it.

 

21 hours ago, MortarThePoint said:

.... but I'd have to be very careful not to ...

 

There's your opportunity right there. Excellent.

 

Do it. Photograph it. Self-build-porn that'll become.

I mean you might even get a compliment from  @SteamyTea 

( mind you it's not Friday yet)

[MortarThePoint]

Well, like Baldric I have come up with a cunning plan. It's on the far left of the options below and involves cutting an undersized notch in the beam, which gets relieved on the post using a router. It also allows a shallower notch in the beam if I cut a slot the top of the post. That slot also serves to constrain the joint laterally. It's kind of a hybrid of traditional and modern.

 

100mm joint with a 85mm Circular Saw depth:

 

100mm joint with a 50mm Circular Saw depth:

[ToughButterCup]

Now that's neat. Remember we want photos.

 

Instinct tells me this is maybe a bit complicated (?) One factor will be the quality of the wood; definitely a case of going to the BM and choosing the wood yourself.

 

German chippies would solve the shrinkage problem with foam😑

[Gus Potter]

On 22/09/2026 at 10:36, MortarThePoint said:

I'm making a simple porch frame to go between two walls and I am pondering between a bridle cut and a simpler to make bolt held option (M12 x 250 Stainless).

Are the posts just there to carry vertical load or is the beam and column acting to resist sideways sway. 

[Gus Potter]

To add a bit. If you use traditional dowels, pegs then there is an old trick that was used in Scotland. We have lots of solid stone walls lined with lathe and plaster on studs on the inside. Timber wedges were driven into the stone work mortar beds. Then they were cut flush using a string line and the studs fixed to them. That is how they got the wall plumb etc. 

 

The spelling differs, as a traditional craft, but they are commonly called Dooks. But the secret was that they would dry the Dook's often near a fire thus they had a really low moisture content. Once they were driven into the wall they expanded. A traditional wall never gets below this moisture content and thus the Dooks always hold tight. 

 

You can use the same principle if you want to peg / dowel the way you are thinking. The dowels will need to be tapered as standard, but to get them really tight dry them out in an oven first. 

 

You could of course use a modern structural glue, but that may be cheating? 

 

 

[MortarThePoint]

54 minutes ago, Gus Potter said:

Are the posts just there to carry vertical load or is the beam and column acting to resist sideways sway. 

 

Limited to the vertical forces really as I thought I would use something like a Simpson String Tie ABR to resist the otherwise unconstrained lateral motion in and out of the U-shaped brickwork. That would be in location B below. In location A I was thinking to have an bolt through an oversized hole and into the brickwork to stablise things during construction.

 

It occurs to me that I could attach a piece of 2x2 to the wall that rides in a slot on the end of the beam. A more modern equivalent would be something like the BTALU90 but not bolted to the beam, just to the wall. That way it wouldn't constrain the beam or posts vertically which I don't want to do due to the shrinkage (admitted small along the grain).

 

It way just be simpler to bolt the end rafters that go along the surface of the wall to the wall and their birds mouths would stop the frame tipping outwards. Some form of slip fixing through the rafter down into the beam could then constrain it from tipping inwards towards the door. Alternatively, I could bolt some wood behind the beam to constrain it, though that would be quite obvious. An advantage of having the final rafters bolted to the brickwork is that they won't move much relative to the brickwork so will limit the movement the lead flashings experience.

 

 

[Gus Potter]

It looks like this is, on reflection,  just an infill roof, like a small canopy that is constrained by substantial walls either side. 

 

Are we over thinking this? Vertical loads could be roof access, at a push, maybe snow dump coming off the higher roof. But the canopy looks like it has a good slope. 

 

I would go back and look at what is Architecturally pleasing, like your proposed joints earlier. 

 

 

 

 

 

 

[MortarThePoint]

25 minutes ago, Gus Potter said:

It looks like this is, on reflection,  just an infill roof, like a small canopy that is constrained by substantial walls either side. 

 

Are we over thinking this? Vertical loads could be roof access, at a push, maybe snow dump coming off the higher roof. But the canopy looks like it has a good slope. 

 

I would go back and look at what is Architecturally pleasing, like your proposed joints earlier. 

 

I'd still have the joints as earlier, but I need to constrain the frame in and out which I feel [1] the bolted end rafters could do nicely.

 

[1] based on my extensive inexperience 🙂

Edited September 24 by MortarThePoint

[MortarThePoint]

I've been busy chopping up the oak posts and beam and have parts ready to cut to length and assemble. Making it 150mm timber is well over twice the effort of something smaller like 100mm. It weighs a over twice as much, so becomes a two person shift and you can't make straight forward cuts using a mitre saw due to maximum cut capacity (120mm in my case). If I was quoting a job like this I would easily double it moving from 100mm to 150mm.

 

An interesting challenge is dealing with even very small bows in the posts. Using geometry and assuming a constant curvature of bow, you can work out that the deviation in the top of the post is eight times the amount of bow [1]. That's pretty significant since over a distance of 2.3m a 5mm bow isn't unlikely, but would shift the top of the post by 40mm. To correct that, you need to remove a wedge from the bottom of the post as otherwise it won't sit flat on the staddle stone. The wider the post, the higher that wedge ends up being. The height of the wedge ends up being four times the bow then scaled width divided by length, so 4 * h * (w / L) [where w post width, L is the post length and h is the bow amount]. For a 5mm bow, that makes for a wedge height of 1.3mm, which if not made would be noticeable. It's only 0.5 degrees from being square, so it highlights how sensitive this all is.

 

That above assumes that you have got your staddle stones perfectly level. Levels are typically accurate to 0.5mm/1m, but that is a based on a perfectly centred bubble. If the bubble is touching the line, you can be out by a fair amount, the exact amount depends on temperature. Based on my level at about 20C, the inner most lines are 10mm/1m (1%, checked by moving a 6mm packer from one end to the other of a 600mm level). I wanted to get my staddle stones more level, but was hampered by the rods underneath (learning) and so most are better that 5mm/1m but one is bubble just touching the line, so 10mm/1m. With the post width of 150mm, that makes for a wedge of 1.5mm.

 

I had hoped to cut the posts square and then fit, but these two about equally sized effects means that I need to test fit, work out what wedge I need to cut and then cut slightly off square. Not a big deal if they weighed less than 48kg. Also, it's fraught with possible errors. I would love it if there was a tool that allowed me to clamp my post held off the top of the stone and then route/plane the bottom of the post guided by the surface of the stone.

 

 

[1]  bow or sagitta of h and chord length L give a radius of curvature r = (h/2) + (L^2 / 8h)  --> r ~ (L^2 / 8h)  since L >> h

angle subtended by the arc of the post theta = L/r --> deviation at top of post, x = L * theta = L^2 / r = 8*h

L2 = (r+w)*theta   ,   dL = L2 - L1 = w*theta   ,   wedge height, y = dL / 2 = 4*w*h / L