Green Building Forum - Last year I helped build my daughter an extension. Sun, 19 Apr 2026 11:24:27 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310460#Comment_310460 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310460#Comment_310460 Sun, 12 Apr 2026 16:34:50 +0100 tony
Document here - https://docs.google.com/document/d/e/2PACX-1vQ2s-HB1cud4gZISwGuQvP8oIifaCVcF94ySusEaaPanqcCf4md3UPJDOKeD02Gg9MitbCVb4vXe5SW/pub]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310463#Comment_310463 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310463#Comment_310463 Sun, 12 Apr 2026 20:47:04 +0100 HollyBush Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310466#Comment_310466 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310466#Comment_310466 Sun, 12 Apr 2026 22:06:26 +0100 tony Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310468#Comment_310468 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310468#Comment_310468 Sun, 12 Apr 2026 22:12:58 +0100 Victorianeco
Couple of questions:

1. Why not an insulated slab instead?
2. Why timber frame as I know you've recommended block as the preferred construction method of your choice previously?

Thanks]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310470#Comment_310470 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310470#Comment_310470 Sun, 12 Apr 2026 22:32:04 +0100 Dominic Cooney Makes our year of thrashing about so far with a still uncertain finish date seem woefully inadequate!]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310471#Comment_310471 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310471#Comment_310471 Mon, 13 Apr 2026 08:12:39 +0100 PeterStarck Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310472#Comment_310472 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310472#Comment_310472 Mon, 13 Apr 2026 08:30:21 +0100 tony Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310473#Comment_310473 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310473#Comment_310473 Mon, 13 Apr 2026 08:32:43 +0100 fostertom
The extg rear elevation is a fine example of brickwork where the perps aren't vertically aligned - quite queezy-looking! Makes you realise the precision and pride of workmanship of the average brickie, when actually such alignment isn't technically necessary.

Can I ask - founds - why 225w below dpc, 150 above? Obviously in this case the wider below dpc will support the brickwork. My question is more general - are you (or anyone) aware of a rule that says found walls (masonry or conc) must be 225w? Unlike for upper walls, BRegs deemed-to-satisfy masonry thickness rules don't seem to specify this, whatever way you try to read it. For instance, in this case if your weather cladding was fixed directly to the stud structure, you wouldn't need any more that a 100w found wall, just to support the stud frame. A considerable economy, in overall footprint, potentially narrower trench, disposal of spoil, manhandling as well as direct cost of heavy materials. What rule of thumb or practical wisdom makes 225w found walls the unquestioned norm?]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310480#Comment_310480 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310480#Comment_310480 Mon, 13 Apr 2026 15:59:35 +0100 tony Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310482#Comment_310482 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310482#Comment_310482 Mon, 13 Apr 2026 18:07:27 +0100 Victorianeco Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310483#Comment_310483 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310483#Comment_310483 Mon, 13 Apr 2026 18:23:08 +0100 tony Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310484#Comment_310484 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310484#Comment_310484 Mon, 13 Apr 2026 18:24:01 +0100 fostertom Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310485#Comment_310485 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310485#Comment_310485 Mon, 13 Apr 2026 22:07:30 +0100 tony Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310486#Comment_310486 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310486#Comment_310486 Mon, 13 Apr 2026 23:18:57 +0100 fostertom Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310487#Comment_310487 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310487#Comment_310487 Tue, 14 Apr 2026 08:03:06 +0100 Peter_in_Hungary Done by a layer of concrete then a layer of stone / rubble then concrete to cover then more stone / rubble etc. to finish with a layer of concrete.

Do you do the same in the UK?]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310488#Comment_310488 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310488#Comment_310488 Tue, 14 Apr 2026 08:22:45 +0100 fostertom
A bit sorry that tony used trenchfill not strip founds with built-up found walls. Yes I know trenchfill saves lots of work, but much more cement - unless using PiH's formula.

Still mystified why laborious expensive shuttered conc was then used on top of it, rather than blockwork. And if doing it that way, why the emphasis on perfectly smooth perfectly levelled trenchfill. Am I missing something?]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310491#Comment_310491 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310491#Comment_310491 Tue, 14 Apr 2026 11:06:10 +0100 sgt_woulds

Rubble trench foundations (with loose stones) are allowed, so this Magyar tormelek/Cement system should be possible with SE signoff in the UK using a modification of the same rules.]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310497#Comment_310497 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310497#Comment_310497 Tue, 14 Apr 2026 12:34:52 +0100 fostertom Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310500#Comment_310500 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310500#Comment_310500 Tue, 14 Apr 2026 16:32:05 +0100 sgt_woulds
There is a video from ACAN about alternative foundations that includes rubble trenches:

https://www.youtube.com/watch?v=I2uGO_1W_Qk


I worked on a strawbale house in the early 2000's that had a rubble trench foundation. The chap was a civil engineer and used rules designed for roadbuilding(?) to get it approved.]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310506#Comment_310506 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310506#Comment_310506 Wed, 15 Apr 2026 10:15:10 +0100 djh Posted By: fostertomAnti-bursting constraint (the rubble fill being extruded outward into softer surrounding ground) much more difficult. Needs looking into - interesting.Car tyres.]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310507#Comment_310507 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310507#Comment_310507 Wed, 15 Apr 2026 10:19:16 +0100 djh Posted By: sgt_wouldsI worked on a strawbale house in the early 2000's that had a rubble trench foundation. The chap was a civil engineer and used rules designed for roadbuilding(?) to get it approved.Our house has a big hole filled with TYpe 2 aggregate, then EPS, then a reinforced concrete slab. It's pretty standard; called a passive slab.]]> Last year I helped build my daughter an extension. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310513#Comment_310513 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18422&Focus=310513#Comment_310513 Wed, 15 Apr 2026 12:46:42 +0100 sgt_woulds
The modern version would be made with foamed (recycled) glass aggregate to provide combined insulation and load bearing. I have used this under my ground bearing slab in my extension, but no reason not to build a passive slab or knee walls off the same material.

In the case of the strawbale house they built a drystone wall upto dpc height, so there was no conrete used anywhere in the foundations. Unfortunately I only got there after the roof was on so I didn't see the build process.

We were adding ground mount solar to power his secret underground bunker...(!)]]>