Fixing for Green Oak

[machtucker]

Hi,

 

I've bought some Eurpoean green oak timber and am now thinking about the best way to fix the crossbeams (2) to the 150 x 150mm posts (1). The decorative rafters (3) on top will also need fixing.

 

I know normal screws/bolts will rust so I should use stainless steel. Given the assembly I don't think dowels are an option.

 

Any ideas or recommendations?

 

Many thanks,

 

Ed

 

[Temp]

What I would do...

 

Slope the top of the post 1 so rain runs off.

 

Fix 2 to 1 with screws, but recess the heads and fill with dowel to simulate pegs.

 

Notch 3 to fit 2. Screw 3 to 1. Don't screw down through 3 into 2 to avoids holes in horizontal surfaces.

 

Ideally slope/bevel all top edges but that needs a table saw.

Edited July 16, 2023 by Temp

[Alan Ambrose]

Traditional oak framing joints + dowels or A4 stainless coach bolts if you want it to look more contemporary. Your design looks like it's halfway to traditional joints already. They don't have to be millimeter perfect - this is rustic green oak right.

 

Robin Clevett has a video or two on YT showing a little bit of green oak work he did.

Edited July 16, 2023 by Alan Ambrose

[machtucker]

On 16/07/2023 at 05:53, Temp said:

What I would do...

 

Slope the top of the post 1 so rain runs off.

 

Fix 2 to 1 with screws, but recess the heads and fill with dowel to simulate pegs.

 

Notch 3 to fit 2. Screw 3 to 1. Don't screw down through 3 into 2 to avoids holes in horizontal surfaces.

 

Ideally slope/bevel all top edges but that needs a table saw.

Nice ideas. I especially like the recessed screws with dowels. I will have to move the position of 3) as at the moment it is situated directly above 1). Also sloping 1 is a good idea. 

[machtucker]

20 hours ago, Alan Ambrose said:

Traditional oak framing joints + dowels or A4 stainless coach bolts if you want it to look more contemporary. Your design looks like it's halfway to traditional joints already. They don't have to be millimeter perfect - this is rustic green oak right.

 

Robin Clevett has a video or two on YT showing a little bit of green oak work he did.

Yes I’m an avid follower of Robin and did see his Oak work. Looked lovely. Would be nice to do something like that but time is not my friend at the moment. Interested to how I could achieve something similar to what I’ve got with dowels alone?

[machtucker]

On 16/07/2023 at 13:53, Temp said:

What I would do...

 

Slope the top of the post 1 so rain runs off.

 

Fix 2 to 1 with screws, but recess the heads and fill with dowel to simulate pegs.

 

Notch 3 to fit 2. Screw 3 to 1. Don't screw down through 3 into 2 to avoids holes in horizontal surfaces.

 

Ideally slope/bevel all top edges but that needs a table saw.

Sloping is possible. Maybe I can set up my circular saw with a fence to do it. How crucial would you say sloping is? The upright posts is fairly straight forward.

 

Also joining the decorative rafters is not as straight forward as screwing 3 into 1 as the rafters are also between posts so I will have to screw 3 into 2 somehow. What about pocket screws at an angle?

[Temp]

40 minutes ago, machtucker said:

Sloping is possible. Maybe I can set up my circular saw with a fence to do it. How crucial would you say sloping is? The upright posts is fairly straight forward.

 

If you plan to let it all go silver its not really important. If you plan to paint it best avoid horizontal surfaces and sharp corners/edges and the paint will last longer. We have a lot of exterior oak treated with ozmo UV Protection oil to keep it honey colour and its the horizontal surfaces that go first.

 

Quote

Also joining the decorative rafters is not as straight forward as screwing 3 into 1 as the rafters are also between posts so I will have to screw 3 into 2 somehow. What about pocket screws at an angle?

 

For the middle one I would screw up through 2 into 3. You can recess the screw head so it doesn't need to be very long.

 

If you go for pressure treated soft wood I've found strimmers cut through the protection on fence posts and they rot out at ground level. Very noticeable as I have some posts that don't get strimmed and others that do. 9n some new posts I wrapped them them with heatshink sleeves designed for fence posts but they are messy and not sure if they work yet.

[machtucker]

Well I’ve bought the Oak. Went for European green oak. Still not sure about painting. We might leave it be for a year or two so it can dry out etc then see what we think. 
 

Although my wife might have other ideas. 
 

 

[machtucker]

On 22/07/2023 at 19:50, Temp said:

 

If you plan to let it all go silver its not really important. If you plan to paint it best avoid horizontal surfaces and sharp corners/edges and the paint will last longer. We have a lot of exterior oak treated with ozmo UV Protection oil to keep it honey colour and its the horizontal surfaces that go first.

 

 

For the middle one I would screw up through 2 into 3. You can recess the screw head so it doesn't need to be very long.

 

If you go for pressure treated soft wood I've found strimmers cut through the protection on fence posts and they rot out at ground level. Very noticeable as I have some posts that don't get strimmed and others that do. 9n some new posts I wrapped them them with heatshink sleeves designed for fence posts but they are messy and not sure if they work yet.

So for fixing 2 to 3 are you suggesting something like this where I drill a hole then a deep counter sink? Then I could use a stainless steel screw 75mm long.

 

[Temp]

2 hours ago, machtucker said:

So for fixing 2 to 3 are you suggesting something like this where I drill a hole then a deep counter sink? Then I could use a stainless steel screw 75mm long.

 

Yes that's it exactly. 

[machtucker]

12 hours ago, Temp said:

 

Yes that's it exactly. 

And then plug the bottom with an oak dowel of some form?

[machtucker]

So the timber is arriving next week and I've been thinking about how I'm going to secure the posts in the ground again. There seems to be a lot of conflicting information on the net.

 

Ideally I would build a concrete foundation and put the oak posts on top of that so they are well out of the way of the soil however due to the design I don't think it will be strong enough. It is not a traditional pergola an is more of a L shaped bit of screening/fencing so there may well be significant side loads. Therefore I have come to the conclusion that I will concrete about 600mm of the post into the ground with a footing about 400 x 400mm square. The posts are 150mm wide.  I obviously want the timber to last as long as possible so have been researching the best way of minimising chances of rot. I will use gravel in the bottom of the foundation hole which will allow water to drain and will also be useful to get the post to the correct height etc. What about sealing/treating the bottom of the post? I have seen guidance that says do and also some that says don't as it can keep water in? Any advice?

 

Cheers,

 

Ed

[Alan Ambrose]

There's a kind of shrinkwrap thing you put on the bottom of softwood posts - meant to be good. As long as it's not waterlogged, being oak, it'll probably last forever anyway.

[Temp]

On 01/08/2023 at 10:56, machtucker said:

And then plug the bottom with an oak dowel of some form?

 

Could do or just leave it open.

[Temp]

23 hours ago, Alan Ambrose said:

There's a kind of shrinkwrap thing you put on the bottom of softwood posts - meant to be good. As long as it's not waterlogged, being oak, it'll probably last forever anyway.

 

I have used these for pressure treated soft wood fence posts but they are messy. When you use a heat gun to shrink the sleeve you get black gloop squeeze out. OK for fence posts but perhaps not for this? Edit: I suppose you could wrap the post with clingfilm or tape to protect it and keep the exposed section clean.

 

 

On 03/08/2023 at 10:46, machtucker said:

I will use gravel in the bottom of the foundation hole which will allow water to drain and will also be useful to get the post to the correct height etc.

 

+1

 

I suppose the L shape might allow fittings like these but I'm not sure about the side loads.

 

https://www.amazon.co.uk/support-bracket-adjustable-Terminal-90X130X8/dp/B01LZGXEPV/ref=asc_df_B01LZGXEPV/?tag=googshopuk-21&linkCode=df0&hvadid=446856026572&hvpos=&hvnetw=g&hvrand=1467536357360235964&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9044886&hvtargid=pla-750585532533&psc=1&tag=&ref=&adgrpid=103463556386&hvpone=&hvptwo=&hvadid=446856026572&hvpos=&hvnetw=g&hvrand=1467536357360235964&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9044886&hvtargid=pla-750585532533

 

 

 

Edited August 4, 2023 by Temp

[Alan Ambrose]

The traditional way to to do this and keep the post and dampness separate would be by using a padstone of course.

[machtucker]

On 04/08/2023 at 19:51, Temp said:

I suppose the L shape might allow fittings like these but I'm not sure about the side loads.

 

https://www.amazon.co.uk/support-bracket-adjustable-Terminal-90X130X8/dp/B01LZGXEPV/ref=asc_df_B01LZGXEPV/?tag=googshopuk-21&linkCode=df0&hvadid=446856026572&hvpos=&hvnetw=g&hvrand=1467536357360235964&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9044886&hvtargid=pla-750585532533&psc=1&tag=&ref=&adgrpid=103463556386&hvpone=&hvptwo=&hvadid=446856026572&hvpos=&hvnetw=g&hvrand=1467536357360235964&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9044886&hvtargid=pla-750585532533

 

 

 

These look great. I'm tempted to go down the concrete foundation with post on top method. No one has told me categorically that I shouldn't do that yet.

[machtucker]

Hi Alan,

 

Yes that is what I'd like to do but I'm worried about the side loads being to strong for the fixing between the post and the padstone. What do you reckon? Do you think a fixing like temp has linked would be strong enough? I suspect it will given the L shape

[Temp]

14 hours ago, machtucker said:

Hi Alan,

 

Yes that is what I'd like to do but I'm worried about the side loads being to strong for the fixing between the post and the padstone. What do you reckon? Do you think a fixing like temp has linked would be strong enough? I suspect it will given the L shape

 

We also have some oak posts on brick plinths. They are located using a length of 20mm stainless round bar sticking up into a hole in the bottom of the post. They hold up a small tiled roof overhang so no need to fix them down. 

 

[Alan Ambrose]

>>> They are located using a length of 20mm stainless round bar sticking up into a hole in the bottom of the post.

 

Yeah, agree - I think I used 10mm last time. A4 rather than A2 SS would be good.

 

This kind of relies on the structure being heavy-ish and stiff-ish in itself i.e. it is expecting to resist shear (crosswise, parallel to the ground) forces only.

 

It looks to me like @machtucker 's structure is light-ish and not very stiff-ish, so maybe buried posts would be good after all. Being oak, they should last probably our lifetimes (making some BH assumptions here  ) anyway. Whereas, I found recently that a treated softwood post with no other protection and in waterlogged soil gave up after 5 years.

[machtucker]

2 hours ago, Alan Ambrose said:

>>> They are located using a length of 20mm stainless round bar sticking up into a hole in the bottom of the post.

 

Yeah, agree - I think I used 10mm last time. A4 rather than A2 SS would be good.

 

This kind of relies on the structure being heavy-ish and stiff-ish in itself i.e. it is expecting to resist shear (crosswise, parallel to the ground) forces only.

 

It looks to me like @machtucker 's structure is light-ish and not very stiff-ish, so maybe buried posts would be good after all. Being oak, they should last probably our lifetimes (making some BH assumptions here  ) anyway. Whereas, I found recently that a treated softwood post with no other protection and in waterlogged soil gave up after 5 years.

Hi Alan. Yes that's my take on it too. I do keep flip flopping between each option however I think I will concrete the post into the ground. I think the fact that there will be quite a large surface area from the panels the forces could be quite strong and with the small brackets mentioned by @Temp the bending moment will be quite large at the bottom Although I'm in quite a sheltered part of Hampshire we can still get some stiff winds blowing through.

 

So the question  is whether it's worth treating the bottom portion of the post or just concrete as is?

[machtucker]

Hi everyone,

 

Well the installation seems to be going OK. I have 5 out of the 6 posts in the ground. I'm now thinking about the fixings (cross beam to the post). I'm going to use stainless steel screws and then use Oak dowels to cover them up. The question is what size screws should I use? An image of the two pieces to be screwed is shown below. Any recommendations greatly received.

 

Correct me if I'm wrong but I'm guessing I should drill the cross beam holes big enough so the screw goes through without biting? I will pre-drill the oak post with a pilot hole so it's not too hard for the screw thread to penetrate.

 

Cheers,

 

Ed

 

Edited October 27, 2023 by machtucker

[Temp]

Stainless steel screws around 100mm. Recess heads about 15mm. So 35mm in the horizontal and 65mm in the vertical. Might get away with slightly shorter.

 

Quite a generous pilot hole as stainless steel screws not as strong and can shear if too much torque needed.

 

[machtucker]

On 28/10/2023 at 08:09, Temp said:

Stainless steel screws around 100mm. Recess heads about 15mm. So 35mm in the horizontal and 65mm in the vertical. Might get away with slightly shorter.

 

Quite a generous pilot hole as stainless steel screws not as strong and can shear if too much torque needed.

 

Thanks for the comment.
 

Yes I’ve heard they are softer. I will try and use a normal steel screw to fix then replace with stainless steel as well as a generous pilot hole. 

[machtucker]

On 28/10/2023 at 16:09, Temp said:

Stainless steel screws around 100mm. Recess heads about 15mm. So 35mm in the horizontal and 65mm in the vertical. Might get away with slightly shorter.

 

Quite a generous pilot hole as stainless steel screws not as strong and can shear if too much torque needed.

 

What diameter of screw do you recommend?