Wind post - is there another method?

[John D v2.0]

We have a 1/4 brick blockwork wall supporting a post holding half the new flat part of the roof and half the old ridge. The se said no issue whatsoever, masonry is strong enough but with the removal of the chimney we had to add a wind post in its place to provide stability against it folding in half.

 

[^woody^]

I dont' know how we managed before windposts were invented in 1986.

 

[wessex101]

The entire gable end on my house was half brick single skin and totally unrestrained at first floor and roof level. It was the only part of the house that was still plumb and not cracking due to subsidence with it's non-existent footing. Good job there weren't structural engineers 200 years ago or it would have fallen down for sure.

 

[John D v2.0]

I dont' know how we managed before windposts were invented in 1986.

The other original end of the same wall has a bit of 2 by 4 nailed to the first floor joists and the ceiling joists, i guess that's the 1920s equivalent. And of course the chimney was a buttess at the other end.
Also we didn't go around taking walls out and going open plan in those days, but the op rebuilding it as a solid wall seems over kill to me.

 

[oxfordite]

View attachment 146720 Your SE has correctly identified the fact that the single-skin brickwork is not suitable to span vertically between the top of the cavity wall and the underside of the roof structure. The critical weak point will be the full-height wall between the windows, because that will be taking wind load on part of the windows each side, as well as its own area.
The wind load induces bending in the brick skin, resulting in tension on the room-side, which brickwork is not capable of resisting. Rather than a chunky wind post, why not consider screwing two (or better, three) strips of steel, say 5mm thick and 100mm wide, to the bit between the windows. These should be suitably fixed to at least two floor joist at the bottom, and to the roof structure (via the wall plate?) at the top.
These would not be true wind posts, but if fixed with sufficient screws, will add some tensile strength to the brick skin as a whole and so improve resistance to lateral wind load.

-- Thanks for this.
Sorry for lack of clarity: single brick = single width of brick = 4.5"
Ground floor wall (and all others) is a 50mm cavity wall.
1st floor wall to front, clad in thick tiles on 1" batten, is single brick, not 9" solid wall.. If they were to use those materials, they'd have continued cavity wall from ground to roof!

One steel fabricator has stated that they have manufactured a DLP post (2nr LP7 posts welded back to back) to create a T-shaped post.
LP? Here: http://iglintels.com/windpost-design/lp-windpost/

So I will ask the SE to do calcs/specification required for that approach.. Then we can resin bond the (short?) leg in to the wall and screw fix the flanges to the wall on each side, and, presumably, screw-fix the top ends (no leg) to the wall plate, and the bottom end, with extra right angle joined to it, either to the top of inner brick wall below, or, to joists at floor level. More cost that standard Wind-Post, but a neater outcome for a straight wall that we can insulate with BASF 4mm grey EPS liner and finish with, maybe, Fermacell 10mm.
Longer term, we will strip the external cladding, insulate and reclad in same old tiles (to satisfy the local authority about appearance and 'being in keeping' etc)

Thanks again.

 

[tony1851]

Just remember that a wind-post is only as good as its' fixings top and bottom.

 

[oxfordite]

Thanks for all replies.
Indeed fixing of the WindPost is key to it actually bracing that section of wall.

There were some interesting designs the SE offered:
- 100 X 100 X 10 RSA; This is a big RSA for a wall 100mm thick..
Bed one side in wall (ie. Cut all the way through the wall!) then frame-fix at 150mm intervals on remaining 100mm side, and via welded lugs on the other.. Yes, with suitable bracket resin fixed below and screw fixed to roof-plate above.
Odd to cut all the way through the wall? Strange to need such a huge steel?
'It's designed to provide ALL the strength' he said. Okay.
- 2no. 70 X 70 X 6 RSAs welded back to back, top of 'T' frame-fixed at 150mm intervals either side in to wall, leg projecting from wall.
- and the 70mm X 70mm square (tube steel) WindPost.. A good strong option..

Finally settled on the last option.. Embedded against the brick (render+plaster skim removed) it will provide 45mm to insulate.. No bad thing.

However, allowing for adequate fixing at top and base, I'm of the opinion that 2no. 50x50x5 RSAs welded back to back and frame fixed (perhaps with some resin too!) at intervals would have sufficed, perhaps with horizontal bracing above ceiling and similarly at floor level..

If there had been both calcs and an indication of the parameters used (to withstand what speed of wind? to exceed necessary strength by what factor?) then I might have obtained a second opinion..
..I did try to do the calcs myself, but it proved beyond me.

Thanks again.