Timber size

[A_Novice]

Guys,

My building reg drawings from the designer show the external walls using timbers 47 X 100.

The building control notes received from the inspector say 47 X 147.

The drawings have been approved.


Which should be used ?

This is for 1st floor timber frame extension over existing garage.

I've asked the designer but concerned they don't match.

Thanks

 

[Notch7]

Well 100mm celetex wont fit between 100 x 47 studs -mostly they are 95mm

Its 11mm osb, not 10mm -anyway, seems thin for sheathing, it is an important structural element.

Im not sure 100 or 147. The bigger section is certainly stiffer.

I would prefer to see a service void on the inside, which the bigger section provides. But then 25mm insulation doesnt work well.

 

[A_Novice]

Thanks. Unfortunately I have limited knowledge so don't completely get all of your post.

On the notes it also says supalux should be used when within 1m of the boundary. This wall is the flank wall and is right on the boundary.

Confused.

 

[Leofric]

What are the building control notes you refer to, are these a schedule of conditions attached to the approval notice ?
What does the designer say regarding the discrepancy on stud sizes ?
Are building control saying it is approved subject to studs being increased to 147mm ?
Comments re wall construction within 1m of the boundary relate to the risk of fire spreading across the boundary to neighbouring property, but you need to ask your designer to liaise with building control and sort it out so you know exactly what has been approved. The designer may need to incorporate any amendments requested by BC on the drawings.

 

[Notch7]

I would start by ringjng the building inspector and ask why

 

[A_Novice]

I would start by ringjng the building inspector and ask why

Thanks I will this morning.

Leofric - the notes I am referring to are titled building control notes and are referred to in the drawings. I.e. please read in conjunction with building control notes blah blah.

The notes also come with a letter saying the drawings are approved and compliant.

Below is the extract I am referring to.

 

[^woody^]

You would normally work to the approved drawing. "100" timbers are fine.

100 Celotex will fit between that timber and the next layer will squash down nicely.

BTW, you don't need c24 timbers for studs, you can't get 10mm OSB, (nor 47 x 100 timber for that matter) and you can't apply a plaster finish to Celotex! Your designer is crap.

 

[A_Novice]

Thanks I will this morning.

Leofric - the notes I am referring to are titled building control notes and are referred to in the drawings. I.e. please read in conjunction with building control notes blah blah.

The notes also come with a letter saying the drawings are approved and compliant.

Below is the extract I am referring to.



View attachment 153970

You would normally work to the approved drawing. "100" timbers are fine.

100 Celotex will fit between that timber and the next layer will squash down nicely.

BTW, you don't need c24 timbers for studs, you can't get 10mm OSB, (nor 47 x 100 timber for that matter) and you can't apply a plaster finish to Celotex! Your designer is crap.

Thanks Woody. Most "professionals" I have been involved with during this process have either been incompetent or severely lacking any attention to detail so it wouldn't surprise me.

 

[Notch7]

my guess is on the inside, you either need insulated plasterboard, or you need battens on the 25mm celetex then plasterboard.

You would then have a service gap for electrics etc.
put in extra battens if you need radiators to hang on the wall.

Maybe talk it through with your builder -drawings are all very well, but they dont show up practical issues, nor order of construction. As it is drawn the insulation would need slots cut to electric cables, electric back boxes and water pipe services.

Ive just noticed there is no air flow behind the external tiles -doesnt there need to be vertical battens first, then counterbattened horizontally with the tile hanging battens? -It looks like the building regs notes mentions.......

You could put the 25mm celetex on the outside, I think?

 

[^woody^]

Ive just noticed there is no air flow behind the external tiles -doesnt there need to be vertical battens first, then counterbattened horizontally with the tile hanging battens? -It looks like the building regs notes mentions.......

Well spotted. Thats poor design and will lead to problems.

 

[A_Novice]

So basically the below is right and the drawings should match them.

 

[^woody^]

There may be some better details posted on here by others, or FMT or me.

A drained cavity is a must with timber frame and the top and bottom details are important - mesh and lead or felt drips. And especially at window heads and reveals at the head or cill, if you don't want water getting into the frame. The designer should detail these, else if you get a bit of a clueless builder, you will be in trouble.

12.5 plasterboard and 3mm skim (not plaster finish) can go directly on the inner face, screwed to the studs. But with this type of thin frame and Celotex, then a denser board or cement board may be better for sound absorbtion.

 

[Leofric]

A Novice , you refer to extract below regarding building control notes but I can't see anything. If you could post images of the letter , approval notice and any schedule of conditions from building control it might clarify things. As far as the external wall construction details are concerned I can't see them either but others have picked up on some good technical points with their comments and in that case I can't see how bldg. control have approved it !
Needs further investigation.
Regards