Brick Colum details needed please!

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I am building a porch extension enclosing two walls at the front of my house. These two walls will provide anchoring for 3 corners of the roof. A pillar will effectively provide support for the 4th. I would appreciate some feedback to my questions to help my decision making.

1) How can I build the pillar to reduce thermal bridging. ( is it the done thing to build the reutrns and interior faces out of blockwork?) I have given up the idea of carrying on cavity into bricks and using cavity closers as the integrity of the pillar would be lost. Do I just build it out of brick and accept the loss?

2) Would it be better to construct with a concrete or mortar core and possibly a steel reinforcement bar through the middle as it goes up? The UPVC units (doors and windows) will be attached to it.

3) Do I attach the roof for tying in purposes or just rest it on top allow for possible timber expansion?

I have included a rough sketch to help describe it:
The porch is 2400 by 1500 with a gable roof over.

Graham
 
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Where is the gable going - over the door or the window?

Either way, you will need a lintel to carry both skins of masonry for the gable and will then either need a return lintel to carry the wall plate or double up a couple of say 8" x 2"s to carry the roof.

These should be enough to stabilize the pillar.

On a standard reg's build a 300mm square pillar would be tight for bearing area to carry two adjacent lintels. You would normally elongate one elevation so that the lintels do not interfere with each other.

Also 300mm square does not work in bricks, try 330mm square.
 
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A 300mm square brick pier is 4 cuts every course and will look a mess

You can have a slender pier with no reinforcement as long as you span a beam across resting on this pier to stabilise it. A cavity pier will also be OK with some thick ties every 225mm

But you don't design a pier in isolation, you have to think of the whole porch design
 
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Thanks for your prompt replies, I suppose that I should have mentioned that the roof construction is purely timber and will be pretty much resting on this corner as well as well as being tied into the existing structure. It will also provide for a 900mm canopy in front of the door where the (wooden)gable is. The timbers will provide for lintels and to match in with the rest of the house the soffit of the porch will be at the top of the window, hence the combining of roof structure timber and lintels. I have done the calcs for pillar loading and I have more than enough compressive strength to take the loads.

The column will be 330 square, sorry Noseall I mis-typed. Thanks Woody for youradvice on the pier. Would the ties go in alternative directions? for example North-South then up 225 to West-East etc if I'm doing a square pillar?
 
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I would not be too concerned with thermal bridging. There wont be a big difference in external and internal temperatures in a porch, so the local condensation risk is low. And heat loss wise it will be negligible too for a porch

You could form a cavity pier and either wrap the internal reveals around or use insulated liners. You will have a 100mm cavity, so if using modern thin SS wire ties then I would put two in per 225mm height - one about 110mm in from the ends. They will always go in the internal to external direction

If you have any older butterfly ties or thicker 4-5mm wire ties then one will do. Just make sure they are good for 100mm cavities ie 225mm long

If the porch is not in an exposed direction, then you could just build the pier as a square and bond it all in with no vertical DPC

The important thing would be to have a [timber] beam across the whole porch width and strap the pier to this, and it will stabilise the whole lot and prevent movement from use of the door. Or a ceiling joist at 90 degrees to the pier could do the same job
 

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