Fri, 24 May 2013 00:40:21 +0100 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107143#Comment_107143 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107143#Comment_107143 Thu, 07 Apr 2011 03:18:10 +0100 wookey
However there is an issue with ensuring the resulting structure is strong enough. Where the junction is with a perpendicular cavity wall there is no problem: notch in the new wall to the old - nice and solid.

However if you have the situation in the attached PDF: new doorway abutting corner of existing house, then there may be a problem. What was a solid masonry external corner is now two separate leaves, relying on the wall ties to hold things up. The timber doorframe and surround can buttress the side-wall, but the front wall is now not well-supported, and it's the one with the wind-loads in this case, and the joist ends (in the inner leaf).

So. How should one deal with this, bearing in mind that the objective was to minimise thermal bridging?

I first thought of putting in stainless helical remedial wall-ties across the cut gap, and filling that gap with foamglass. That should work. Anyone have any idea how many such fixings is 'enough'? My builder reckons one every 3 courses. I assume that such ties are deemed to have no structural properties except along the line of the tie (i.e the sideways loading they will resist is negligible)?

Then I thought, well, actually if those ties will do then why not use teplo ties instead for less bridging? They would have to be epoxied in - can one do that?

The design does have a built-in 'buttress' on the corner which may be enough to decide not to worry about it unduly, but I'm interested in the general answer here, not just my own case - it serves merely as an example of the class of problem.

The other side (garage wall) is even more interesting - that's 9" brick and we don't have a handy corner giving access for ties.

How do we think this stuff should be dealt with?

http://wookware.org/extension/drawings/thermalbreakdetail.pdf]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107144#Comment_107144 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107144#Comment_107144 Thu, 07 Apr 2011 07:14:32 +0100 tony
If it were mine I would cut out bit where you show foamglass and fill it with whatever cavity insulation is used in the cavity. I would not bother with the ties! How high is the extension? single or two storey? I would cut out up to 300mm above ceiling level for single storey but most people would bridge the cavity even worse with a steel lintel making a nonsense of breaking the bridge up the wall.

An engineer may want some strengthening if you didnt have the external pier, the BI probably wont notice. For two storeys an engineer would be the safe option

I would rather see the door set back a bit more from the corner for esthetic reasons making everything stronger.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107173#Comment_107173 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107173#Comment_107173 Thu, 07 Apr 2011 11:14:32 +0100 fostertom http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107179#Comment_107179 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107179#Comment_107179 Thu, 07 Apr 2011 13:04:40 +0100 djh Posted By: tonyI would rather see the door set back a bit more from the corner for esthetic reasons making everything stronger.
+1]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107222#Comment_107222 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107222#Comment_107222 Thu, 07 Apr 2011 20:31:22 +0100 joe90 ]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107228#Comment_107228 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107228#Comment_107228 Thu, 07 Apr 2011 23:51:51 +0100 tony
He was goo though and a realist, I used to meet them like that but they are few and far between now.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107234#Comment_107234 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107234#Comment_107234 Fri, 08 Apr 2011 02:54:36 +0100 wookey
As you say the building inspector won't even notice. In this case I'm the structural engineer :-) I'll read the eurocodes to see what they have to say about it.

Why set the door back more than 100mm? You reckon it looks nicer? This matches the windows.

Fostertom, EWI on the front face of the house is actually quite likely eventually, which will make the thermal break treatment somewhat redundant. I still think it's worth while, as EWI may be a while coming.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107235#Comment_107235 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107235#Comment_107235 Fri, 08 Apr 2011 03:12:45 +0100 wookey
Laying without mortar between perinsaul blocks both offsets the blocks from the brick coursing vertically and leaves a long diagonal somewhat weaker than it was. There is mortar on either end of the block, just not in the middle. I can't decide if that's actually a problem or not. The foamglas technical chap recommended putting in the mortar and accepting the corresponding bridging.

The really radical version would be cutting a diagonal with an angle-grinder and putting them in as if it was a normal course. This leaves things well-mortared, but again I'm not sure how wise it is. This sort of thing is not unheard of - tumbling-in produces a similar arrangement, but usually only for 3 bricks or so. This would be a 2.5m run.

These show the stepped version (with 100mm thick blocks)
http://wookware.org/extension/builders/pdf-drawings/details/cut-in_blocks_section.pdf
http://wookware.org/extension/builders/pdf-drawings/details/cut-in_blocks_layout.pdf]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107257#Comment_107257 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7238&Focus=107257#Comment_107257 Fri, 08 Apr 2011 13:28:30 +0100 djh Posted By: wookeyWhy set the door back more than 100mm? You reckon it looks nicer? This matches the windows.
The idea is that a door should be more significant than windows so that your attention is drawn to it as you approach the house. Take a walk up Hills Road and look at the front doors.

Plus of course, the real point is that it gives you a return to stiffen the wall.]]>