PFC's - how to install

[icornish]

Hi,

My structural engineer has specified 2PFC's to support the brick wall above where I am due to knock out.

I understand that I put the PFC so the top flange supports the wall above. However, I am not clear in how or if I need to bolt/join the two PFC's to each other to bridge the cavity (so, one PFC each side of the cavity), or if it's 2 PFC's bolted together each side of the cavity.
Ordinarily, I'd contact my structural engineer but he's on holiday for a few weeks

Appreciate any help that can be offered

 

[RonnyRaygun]

Bolt them back to back with square or round tubes in between to suit the cavity width.

Tubes at 600mm centres along the length of the beam, staggered top to bottom, say 50mm from top, then 50mm from bottom, and so on.

M16 bolts through the PFCs and tubes.

 

[icornish]

Thank you - just what I needed!

 

[ryme64]

Hi,

My structural engineer has specified 2PFC's to support the brick wall above where I am due to knock out.

I understand that I put the PFC so the top flange supports the wall above. However, I am not clear in how or if I need to bolt/join the two PFC's to each other to bridge the cavity (so, one PFC each side of the cavity), or if it's 2 PFC's bolted together each side of the cavity.
Ordinarily, I'd contact my structural engineer but he's on holiday for a few weeks

Appreciate any help that can be offered

would love to know why he has specified two channels

 

[RonnyRaygun]

would love to know why he has specified two channels

Because if you have a 300mm wall you will need a plate welded to the top of a single UC section.
May also be that PFCs can be less high than using UC or UB sections. For example, a pair of 180x90 PFCs might work where a pair of 178x102 UBs wouldn't, and in turn they would be less high than 203x102 UBs or a 203x203 UC.

 

[ryme64]

would love to know why he has specified two channels

Because if you have a 300mm wall you will need a plate welded to the top of a single UC section.
May also be that PFCs can be less high than using UC or UB sections. For example, a pair of 180x90 PFCs might work where a pair of 178x102 UBs wouldn't, and in turn they would be less high than 203x102 UBs or a 203x203 UC.

Why would you need a plate welded to it. Have come across it far too often.

A pair of channels financially is a horrendous cost compared to either a pair of ubs or a uc.

And if a pair of channels are specified, surely how they should be connected is just as important.

 

[RonnyRaygun]

Why would you need a plate welded to it. Have come across it far too often.

How are you going to sit a 300mm cavity wall on a beam 203mm or less wide? At best you will have almost 50mm overhang of a 100mm leaf...not great for stability...hence the requirement of a plate welded to the top flange.

A pair of channels financially is a horrendous cost compared to either a pair of ubs or a uc.

Yes, but I've already given reasons why it may be better to use PFCs. The cost of a UC section goes up considerably once you have to weld a plate to the top, and often PFCs have a higher capacity than a UB so a UB might not even be an option.

And if a pair of channels are specified, surely how they should be connected is just as important.

I agree with that...detail I gave is pretty standard, and the OPs SE should have given something similar.

 

[RonnyRaygun]

Hold on...that's not you is it Grrrraint???

 

[ryme64]

Why would you need a plate welded to it. Have come across it far too often.

How are you going to sit a 300mm cavity wall on a beam 203mm or less wide? At best you will have almost 50mm overhang of a 100mm leaf...not great for stability...hence the requirement of a plate welded to the top flange.
Corbel the brickwork.

A pair of channels financially is a horrendous cost compared to either a pair of ubs or a uc.

Yes, but I've already given reasons why it may be better to use PFCs. The cost of a UC section goes up considerably once you have to weld a plate to the top, and often PFCs have a higher capacity than a UB so a UB might not even be an option.
I find it hard to believe that in a standard domestic opening
that a pfc would be advantageous.

And if a pair of channels are specified, surely how they should be connected is just as important.

I agree with that...detail I gave is pretty standard, and the OPs SE should have given something similar.

Am not trying to be argumentative, just cannot see why the OP was specified pfc's

 

[RonnyRaygun]

Am not trying to be argumentative, just cannot see why the OP was specified pfc's

But can you see now that I've explained it?

It is you, isn't it Grrraint??? Both from Hampshire, writing style very similar...I'd put money on it

 

[ryme64]

Am not trying to be argumentative, just cannot see why the OP was specified pfc's

But can you see now that I've explained it?

It is you, isn't it Grrraint??? Both from Hampshire, writing style very similar...I'd put money on it

Not at all. still cant see why they were specified. Not even any thought of installing them. extremely unstable.

 

[RonnyRaygun]

Tenner says it's Grrraint

 

[ryme64]

Tenner says it's Grrraint

That will be a tenner you owe me.

Merry Christmas.

 

[icornish]

Thanks for a very interesting read!

The span is 3.8m, so I'm not sure if that has any bearing on matters (pun intended!), supporting two solid brick walls(and the cavity) and roof.

I'm not overly worried about the cost, as long as the walls stay up!

 

[icornish]

Hi all, again!

Been working through the calcs given by my engineer (whos still unavailable), and it looks like I might get away with putting in a 152x89x16UB for the span.
Whilst I would await the return of my engineer, or finding a new one (Any recommendations in the Surrey area?) before ordering/proceeding.. does it seem reasonable?

Span in 3.8m,
Wall load is 5.7KN/m
Roof DL = 4.2
Roof U = 3.2
1st Floor D = 1.5
1st Floor U = 4.7
(These are for the inner wall - the outer wall is obviously a lower loading due to the lack of 1st floor beams etc)

Whilst I follow the engineers calcs ok, where I struggle is the conversion of the forces (total KN/m) into a suitable beam. Currently specified as a 200x90 PFC, I'd prefer it as a "bog-standard" UB if possible for consistencies sake.