Gavin’s timber frame thread

[gavztheouch]

Hi I’m in the process of designing my timber frame. I thought I’d start a thread to pick some brains as I go along.

 

The frame will be c24 225mm by 45mm timber with a breathable racking board on the outside plus 60mm wood fibre.

 

I have engineering and architect drawings and designs. My next job will be to create my own drawings to use myself or pass on to a joiner to complete the actual work.

 

I’m using a cad program called fusion 360 and I plan to 3D print the design to give me motivation and a nice visual model to refer to. I used to build prototype machines in the workshop without drawings, now that I’m older and wiser (hopefully) I find that concept laughable. I need a clear plan to refer to. I’m going to make mistake building this house. I have some time before the spring, building the frame in cad will hopefully help me make at least some of them in the computer before I take it to site.

 

Below is a practice part of the wall. Printed at 3.5% of the original. 

 

[JohnMo]

Have looked at Larson strut for the walls? Your 225mm studs will create a thermal bridge at each strut. Which you are mitigating with external insulation.

 

The Larson strut, uses 2 smaller studs joined together with ply or OSB. So you would have say two 4x2s, or a 3x2 and a 4x2 with a gap between, the gap maintained by several pieces of the OSB nailed to each stud. One stud is structural The other to form a depth for insulation. The thermal bridge becomes the cross section of the OSB instead of the stud. You can make a good depth of wall for insulation and could save the time and effort of external insulation as well.

 

 

[JOE187]

225 x 45 c24 is a heavy frame to stand up!

I think you would need lifting gear for all exterior panels.

Have a look at this video series for wood fibre.

 

https://www.cairncollab.com/buildingpassivevideoseries/v/bishop-passive-house-introduction

[ProDave]

My first question is what are you planning to put on the outside of the wood fibre EWI?

 

I take it the idea is full fill of the frame with insulation?  The reason for it being so thick is to get the extra insulation depth.  My house frame is all 195 *45.

[Russell griffiths]

Trying to buy dry straight 225 timber will be a pain, I would look at i joists for a better construction. 

 

Or twin wall as mentioned. 

[Iceverge]

18 hours ago, JohnMo said:

Have looked at Larson strut for the walls? Your 225mm studs will create a thermal bridge at each strut. Which you are mitigating with external insulation.

 

The Larson strut, uses 2 smaller studs joined together with ply or OSB. So you would have say two 4x2s, or a 3x2 and a 4x2 with a gap between, the gap maintained by several pieces of the OSB nailed to each stud. One stud is structural The other to form a depth for insulation. The thermal bridge becomes the cross section of the OSB instead of the stud. You can make a good depth of wall for insulation and could save the time and effort of external insulation as well.

 

 

 

I love all this .

 

Larsen trusses. Double stud walls, truss walls etc. Dense pack cellulose of course if you can too. 

 

They really shine where you need to hang the cladding from the structure as you can nail or screw easily into the studs. 

 

Where they fall down a bit is the ease of insulating properly around door and window frames. EWI systems really shine here. I like the fact that they keep all the wood products good and warm year round too. 

 

 

 

 

 

 

[Alan Ambrose]

>>>

I have engineering and architect drawings and designs. My next job will be to create my own drawings to use myself or pass on to a joiner to complete the actual work.

 

I’m using a cad program called fusion 360 and I plan to 3D print the design

<<<

 

It might be worth checking with the trades concerned that they're really going to follow your detail drawings. I think a lot don't ... and just use whatever 'system' they've used to-date. If you do prepare drawings you'll need to walk through them in detail and get the trades to agree on the detail with you - even then they may make it up as they go along if you're not watching. I think this particularly applies to 'newfangled' practices like insulation continuity / airtightness / insulated pipes / radial circuits etc etc.

 

FWIW I'm using Fusion also - not the best, but passable both for architectural and engineering drawings. You reminded me that I planned on getting a 3D print of our design for review purposes. Fusion also has load analysis and heat analysis which I have played with but not used extensively.

 

You might want to check out J Harris spreadsheet /  https://www.ubakus.de/ / the Passivehaus spreadsheets for heat and condensation analysis. Maybe those calcs were done by your architect/engineer already - in which case you should have U value numbers already.

 

 

[Iceverge]

Rather than 3D printing something I think it's actually a worthwhile exercise to make something out of plywood.

 

Not cardboard or balsa wood.

 

Get some 9mm ply that you need to jigsaw and drill. It gives you a really excellent feel for how hard it is to build something at scale. 

 

 

 

 

[Iceverge]

Rather than 3D printing something I think it's actually a worthwhile exercise to make something out of plywood.

 

Not cardboard or balsa wood. Some 9mm ply that you need to jigsaw and drill. It gives you a really excellent feel for how hard it is to build something at scale. 

 

 

[gavztheouch]

 

 

A similar construction here in this video. I have an external breathable racking board and I also noticed my studs are actually 245mm not 225mm. Its definitely a worry regarding the warping with such a large piece of wood. About 8 months ago I made a test section of wall from c24 245mm, there is no racking boards fitted and everything is still straight. I still have about 40 or 50 pieces of 245mm by about 3.6m sticks, it might be worth going through them all to see how badly twisted they are? So far my intuition tells me they are pretty stable along their length, maybe more so than the smaller sections like 2x4, but obviously across their width there will be lots more cupping and shrinkage. If I let them dry out somewhat then they won't shrink much more but it will be impossible to savage twisted/cupped lumber that could have been used when wet. The theory being if you nail them quick enough together they should be prevented from twisting in situ. Not sure I 100% subscribe to this theory.

 

Another possibility would be to buy more wood than I need and let it all dry out in the shed over the next few months and then select the best ones to use in the house. The rest I could cut up for shorter lengths?

 

 

[Iceverge]

On 25/12/2023 at 21:47, gavztheouch said:

Hi I’m in the process of designing my timber frame. I thought I’d start a thread to pick some brains as I go along.

 

The frame will be c24 225mm by 45mm timber with a breathable racking board on the outside plus 60mm wood fibre.

 

I have engineering and architect drawings and designs. My next job will be to create my own drawings to use myself or pass on to a joiner to complete the actual work.

 

I’m using a cad program called fusion 360 and I plan to 3D print the design to give me motivation and a nice visual model to refer to. I used to build prototype machines in the workshop without drawings, now that I’m older and wiser (hopefully) I find that concept laughable. I need a clear plan to refer to. I’m going to make mistake building this house. I have some time before the spring, building the frame in cad will hopefully help me make at least some of them in the computer before I take it to site.

 

Below is a practice part of the wall. Printed at 3.5% of the original. 

 

 

I'm assuming this is an external wall?

 

From an amateur look at it I have a couple thoughts regarding thermal bridging and timber use. 

 

1. I don't think noggins are required assuming you have a structural racking board one side of the wall.

2. There's an awful lot of jack studs, consider clips or splitting them.

3. Have a look at mindsparx video on you tube and his framing. Particularly the Hammer-Band as he calls it. It does away with individual headers and uses one of the top plates on edge instead around the whole perimeter. 

4 The double bottom plate could go I think. 

5. I'm guessing the breathable racking board is something like Medite. You could move to something cheaper like OSB internal to the studs as a racking and use the T&G Gutex externally on its own like @ProDave although I don't think rendering it is the way forward in a wet climate.  Then tape the OSB for airtighess. 

 

WHat is your final external rain screen? Bricks/blocks or timber/fiber cement cladding. 

 

 

 

 

[Iceverge]

https://youtu.be/4nRz0D0bNmg?si=p_0DA455ijXADWUk

[gavztheouch]

Progress so far, I have taken out the repeating studs at 600mm centres for clarity to focus on the important bits

[Gus Potter]

57 minutes ago, gavztheouch said:

Progress so far, I have taken out the repeating studs at 600mm centres for clarity to focus on the important bits

Well done you for giving this a go..

 

If you want I can give you a few pointers on what you need to do to get the preliminary sizes for you timber frame (TF) and the grades of timber you may need.

 

To do that I would need to know..

 

A: The floor plan dimensions, location of the internal load bearing walls roof pitch and need to know about any funny loads you are introducing.. pool tables ect..

 

B: The ground, first and second floor levels.

 

C :The sizes of the openings.. windows and doors.

 

D : Your post code so I can assess the wind and snow loading.

 

I'm minded to give this a go with my SE hat on as..

 

1/ You have made a good effort.

 

2/ It may help other folk on BH understand what goes into the preliminary sizing of a timber frame.

 

 

 

 

 

 

 

 

Edited January 13 by Gus Potter

[gavztheouch]

51 minutes ago, Gus Potter said:

Well done you for giving this a go..

 

If you want I can give you a few pointers on what you need to do to get the preliminary sizes for you timber frame (TF) and the grades of timber you may need.

 

To do that I would need to know..

 

A: The floor plan dimensions, location of the internal load bearing walls roof pitch and need to know about any funny loads you are introducing.. pool tables ect..

 

B: The ground, first and second floor levels.

 

C :The sizes of the openings.. windows and doors.

 

D : Your post code so I can assess the wind and snow loading.

 

I'm minded to give this a go with my SE hat on as..

 

1/ You have made a good effort.

 

2/ It may help other folk on BH understand what goes into the preliminary sizing of a timber frame.

 

 

 

 

 

 

 

 

Gus that is extremely generous of you. Thankfully I have already had the frame engineered by a SE. This exercise is mainly to work out the construction details and find mistakes in the drawings. I’ve found a few so far. I would very much appreciate your eye as the project progresses.

[gavztheouch]

Cad work is done for now. Meeting with the architect next week to try and finalise most of the window sizes and some other details. Almost finished printing the parts for the model and made a start tonight glueing it together. I’m using PLA plastic for the prints and super glue to stick it together.

[gavztheouch]

Model finished ready for review with architect to sort out window sizes and positions. I haven’t added the dormer windows yet. Going to call an end to the modelling for now and focus on the foundations.

Edited January 24 by gavztheouch

[gavztheouch]

Joiners arrived today to check out the slab. They plan on starting on Monday. Just noticed that all my timber engineered lintels that I have yet to purchase are all non standard in dimensions and also in grade. They are GL28h, only GL24h is kept in the uk everything else needs to be ordered with a 1 month lead time. 

 

I don't know why he would use such a specific and hard to get beam. I could redesign the beams to be stock uk items but this will take time and cost me his time I would guess. 

 

Definitely feels like I'm lurching from one expensive balls up to the next. 

 

Also just found out the scaffolding will be in the region of £16k, I was budgeting for around 2-3K.

[gavztheouch]

Anyone know where I can get GL28h from stock?

[Kelvin]

£16k? How big is the footprint and how long is it booked for.  I planned to have the scaffolding up for 13 weeks but due to balls ups it was up for 17 weeks. Total cost was £4500. 

[gavztheouch]

Hi Kelvin its 110m2 basic rectangle with porch sticking out.

 

The £16k was the joiner telling me how much his last two project were. I think they were bigger footprint with more technical bits sticking out but somewhat comparable. It was up for over a year I think.

 

Where about's in Perthshire are you? Would you mind sharing the details for your scaffolder? How long ago was your build.

 

My dad has about 50% of the quick stage scaffolding needed, another option would be to buy the remaining parts I need and then get someone to build it and get a ticket on it. Not sure how hard that will be to get someone to do that but things are quieter in the building trade now.

 

@Gus Potter My engineer was a fixed price job about 5-6K if I remember. What is the protocol when I start asking lots of questions that take up the engineers time. Is this included in a fixed package or should I be looking to pay for his time. My view is I am clarifying his original design and not asking for new work but I'm not sure.

 

 

[Kelvin]

A little over a year ago. 170m². Near Blairgowrie. We used Perth Scaffolding. We also only scaffolded three sides as we needed access on the North elevation for the tele-handler. However I had enough scaffold on-site for all four elevations. 

Edited August 17 by Kelvin

[Kelvin]

35 minutes ago, gavztheouch said:

 

 

@Gus Potter My engineer was a fixed price job about 5-6K if I remember. What is the protocol when I start asking lots of questions that take up the engineers time. Is this included in a fixed package or should I be looking to pay for his time. My view is I am clarifying his original design and not asking for new work but I'm not sure.

 

 

My experience was any questions specifically to do with their work was free. Anything additional to the original work was charged at an hourly rate. 

[saveasteading]

15 hours ago, gavztheouch said:

scaffolding will be in the region of £16k, I was budgeting for around 2-3K.

Scaffolding quotes can vary dramatically. It can depend on whether they have capacity and loads of poles in stock, or have to cross-hire more in.

If one is quiet they might not even put much hire value on the poles.

Do you mind rusty old stuff as long as it is legal?

Make sure the scaffolding is as your contractor needs. sometimes too much is erected. other times they want the deck levels changed. the joiner might want a different arrangement to the roofer. return visits cost.

Will there be any weekly hire charge? How certain is your time frame?  If the scaffolder says there is a charge after, say, 12weeks, that is an easy wrangle to get 16.

 

That said, I always under-cost scaffolding. It is a habit from the old days when towers were sufficient.

Also I have noticed a move into less shouty-sweary workers. I would love to know what has changed.

 

 

[gavztheouch]

Just noticed my joiner has fixed the sole plate down with 7.5 x 120mm concrete screws at 400mm centres into my slab. The fixing schedule calls for rawl bolt concrete anchors which are M8 x 120mm.  These Rawl bolts are actually 10mm in diameter so prob more of a difference than he thought. I looked up the specs and the 7.5mm concrete screws hold about 1.8kn while the rawl bolt anchors hold 24kn so more than ten times as strong. Stuff like this drives me mental especially as we live in a very windy site,  I think it is also prob not an issue as the house will probably weigh enough to hold itself down. This is why self build is so stressful if you are a perfectionist in the mechanical/structural stuff. 

 

Possible fixes I can think of if it's an issue are.

 

1. remove the screws and drill bigger, the 7.5mm screws are actually 7.5mm so a 8mm drill should clear out all the concrete that has been cut by the flutes leaving a new hole to start again. Downside is I will need to get bolts and take the time to do it. They were going to stand the walls tomorrow. We don't have the floor joists or scaffolding for three weeks so there will be a break in the meantime anyway. Could not stand the wall and change the bolts anyway

 

2. Forget about it and don't tell building control or the engineer.

 

3. Leave the screws in and fix longer correct bolts near the originals. I don't like this so much as I dont know where the old screws are. I could mark the sole plate for the screw locations, possible fix for that issue.

 

There are also about 15 heavy duty glued in hold down brackets on the gables and front wall. The engineer hasn't replied yet but I'm assuming these will be the main hold down/racking points and maybe the concrete screws are redundant. If this is the case that just leave the back wall to fix down. 

 

Edited August 21 by gavztheouch