Wall studs at 400mm centres

[Thorfun]

Hello,

 

can someone please explain to me the benefits or drawbacks of using 400mm centres for external walls in a timber frame? I've had a quote from a company that is using 400mm centres and it's the only one from the various quotes I've had. all other manufacturers are using 600mm centres.

 

apart from the obvious worse U-value due to more timber in the walls. what are the other good/bad reasons for using the narrower centres?

 

cheers.

 

ps. after attending the NHBC webinar on timber frames I am now aware that if you're not using a double header plate on the wall panel then the ceiling joists need to be in line with the wall studs. so I guess this could be a reason as the suspended floors on the quote are specified to be 400mm centres as well. but I would've thought that from a manufacturing perspective it would be cheaper to use a double header plate than to use more studs in the wall. but, maybe I've just answered my own question and it's because the joists need to line up with the studs! ?‍♂️

[A_L]

17 minutes ago, Thorfun said:

maybe I've just answered my own question

 

partly, studs carry loads from the roof and you may need more to take this, also the width of a stud could be less at 400mm centres e.g. 89/100mm instead of 140mm

[Thorfun]

9 minutes ago, A_L said:

 

partly, studs carry loads from the roof and you may need more to take this, also the width of a stud could be less at 400mm centres e.g. 89/100mm instead of 140mm

thanks for the response. but the quote is for 140x38 CLS (C16) kiln dried stud work and none of the other companies feel I need 400mm centres and are using the same sized studs.

 

I'm just confused why this company would. I have asked them, btw, I'm waiting for a response.

[A_L]

@Thorfunmaybe they just have a more risk averse structural engineer or software design package

[Thorfun]

17 minutes ago, A_L said:

@Thorfunmaybe they just have a more risk averse structural engineer or software design package

yep! I guess it could be as simple as that. ?

[Mr Punter]

With 400mm v 600mm centres the actual percentage timber will not be much more.  Loads of timber is in double studs at openings, corners, top and bottom rails, sole plates, top plates and locating plates.  It will make more of a difference on a long wall with no openings but this is not typical in a house.

[TerryE]

We've got our wall cassettes and flooring on 400mm centres.  Everything is just that bit more solid, IMO, compared to friend's house where he had 600mm centres. 

[Jeremy Harris]

+1 to the above re: 400mm centres. 

 

The last timber framed house we lived in had studs at 600mm centres, and by comparison this house feels noticeably more solid.  You notice it especially if a door bangs, when there's virtually no shake anywhere.

[joe90]

+1 to all the above, my flooring joists were spec at 600ctrs but my builder, like me, always go 400. Floor is soo much more solid.

[Thorfun]

thanks all. it's very interesting and good to know that a 400mm centre walls/building feels more solid. from the online U-value calculator the 400mm studs adds 0.003 to the U-value which is so little it isn't really worth mentioning!

 

for me this is another tick in the good box for this company. ?

[Carrerahill]

20 minutes ago, Thorfun said:

thanks all. it's very interesting and good to know that a 400mm centre walls/building feels more solid. from the online U-value calculator the 400mm studs adds 0.003 to the U-value which is so little it isn't really worth mentioning!

 

for me this is another tick in the good box for this company. ?

I'd say there are fairly few drawbacks to a 400mm centres stud work concerning the end result, the issues are probably more for likes of insulating, depending on how they are going to insulate it will mean more pieces and more cutting, something I would have not enjoyed when it was the PIR insulation. There will be a slightly reduced thermal efficiency as you noted but this will no doubt be mitigated. 

 

I personally went for 145x45mm (2x6) for my TF, I went for 600mm centres but placed noggins and blocking at key locations to give a more solid feel and to help with attaching things to walls like TV's and kitchen cabinets and hooks and pictures and shelves all sorts. 

 

140x38 CLS does seem a bit less sturdy than a proper 2x6 so could be why he wanted the 400mm c/c.

 

 

 

 

[Thorfun]

37 minutes ago, Carrerahill said:

I'd say there are fairly few drawbacks to a 400mm centres stud work concerning the end result, the issues are probably more for likes of insulating, depending on how they are going to insulate it will mean more pieces and more cutting, something I would have not enjoyed when it was the PIR insulation. There will be a slightly reduced thermal efficiency as you noted but this will no doubt be mitigated. 

 

I personally went for 145x45mm (2x6) for my TF, I went for 600mm centres but placed noggins and blocking at key locations to give a more solid feel and to help with attaching things to walls like TV's and kitchen cabinets and hooks and pictures and shelves all sorts. 

 

140x38 CLS does seem a bit less sturdy than a proper 2x6 so could be why he wanted the 400mm c/c.

 

 

 

 

 

they use glass wool within the stud work covered in PIR (which seems pretty standard) and so would be easier to fit without gaps.

 

it seems that 140x38 are the stud of choice as all the quotes I've had are using that size timber stud. one company did offer a 184mm wide stud though as an option.

[Carrerahill]

6 minutes ago, Thorfun said:

 

they use glass wool within the stud work covered in PIR (which seems pretty standard) and so would be easier to fit without gaps.

 

it seems that 140x38 are the stud of choice as all the quotes I've had are using that size timber stud. one company did offer a 184mm wide stud though as an option.

Matchstick wood is used by the production builders these days but doesn't make it good or right. I'd push, if this is your build and maybe your forever home I'd think about it.

 

See what others on here think. 

[Thorfun]

5 minutes ago, Carrerahill said:

Matchstick wood is used by the production builders these days but doesn't make it good or right. I'd push, if this is your build and maybe your forever home I'd think about it.

 

See what others on here think. 

 

it's an interesting point of view and I will definitely bear it in mind when making a final decision on manufacturer. thank you.

[JOE187]

I also built 6x2 at 600c with nogin  and used 11mm osb3 nailed and glued on exterior,  rockwool 140 flexi slots straight in tight and then tyvek airguard and 25mm service cavity  nternal.

[Carrerahill]

16 hours ago, JOE187 said:

I also built 6x2 at 600c with noggin  and used 11mm osb3 nailed and glued on exterior,  rockwool 140 flexi slots straight in tight and then tyvek airguard and 25mm service cavity  internal.

This is pretty much the make-up I used, only difference being I used ridged 100mm insulation within the 2x6's.

 

As you say it leaves a decent service void.

 

2x8 blocking was added where I felt necessary to allow simple fixing of things to the walls and to give a more solid feel at various sections of the wall such as near doors which may result in the wall getting a thud.

 

 

[Oz07]

My understanding is cls has a lower moisture content than standard carcassing so moves less when settling 

[scottishjohn]

maybe another advantage of SIPS panels -the foam will give gret rigidity as well as insulation and air tightness?

Edited April 10, 2020 by scottishjohn

[DavidFrancis]

@Oz07 at the builders merchant I use (a big and busy independant) they store all structural timber outside, unprotected. So if you pick a less popular size, from the bottom of the stack, after a prolonged wet period, then your timber could be soaking wet. I had to repair the edge lip of our flat roof a few years ago. It was made partly of (sawn) batten and partly of planed timber. The planed timber was fine  but parts of the batten had rotted away. I suspect the batten was wet when it got covered by the felt.

 

I have the impression you work with timber a lot. What's your view on the way timber is stored?

[Oz07]

Funnily enough merchant I use keeps carcassing outside although covered over with the wrapping the pa ks coming but cls inside. I know another merchant who does the same. I'm pretty certain cls should have a lower moisture content by definition. Ideally I suppose it needs to stabilise before you wrap any timber else like you say trapping wet in

[Hobbiniho]

one of the builders merchants here (jewsons) stores CLS outside on racks and the other (buildbase) stores it in an old shed so is generally dryish, i think it depends on what you are doing, if you are building a kit that is going to be exposed to the weather for a while when you are getting it wind and water tight there is little point in buying dry wood, although wet wood is a pain to work with as it is harder to make marks on and you get wet cutting/ moving it