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jpinthehouse

Improvement on block and beam foundation insulation

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Thanks for the earlier replies, am now using block and beam on trench blocks, looking at reducing.  thermal bridging under sole plate of timber frame

Thanks

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I had the same question and have decided to do the following...

 

Our frame is quite wide at 245mm so we're splitting our sole plate into 2x95mm plates and insulating the gap between to minimize the primary bridge through solid timber. In addition to this we're using insulation on the external face of our block-work upstand which basically sandwiches it between this and the internal insulation. Hopefully this should help reduce the risk of condensation build up which to be honest was my larger concern than the cold bridge.

 

How wide is your wall?

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Hi

100mm block work 50mm cavity and 140mm stud sitting (as it stands)  165mm of block make up which sit on beam floor which in turn sits on trench blocks 

Hope this makes sense 

 

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Think foamglass type blocks are the accepted workaround here? Also look into using eps insulation instead of lean mix Conc in your cavity below ground. Will resist compression and reduce cold bridge. Cut a champher on top to direct water outwards. Did @joe90 do this?

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15 minutes ago, Oz07 said:

Also look into using eps insulation instead of lean mix Conc in your cavity below ground. Will resist compression and reduce cold bridge. Cut a champher on top to direct water outwards. Did @joe90 do this?

 

No it’s me that did it and worked really well. Needs a big (600mm) step DPC but is very effective. 

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Why, does the dpc go under the eps then?

 

Also is this method more successful with ground bearing Slab as inside face of internal blockwork will also be at low temp in vented floor? Suppose eps could also be placed against this face for belt and braces?

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35 minutes ago, PeterW said:

 

No it’s me that did it and worked really well. Needs a big (600mm) step DPC but is very effective. 

 

 

Well great minds think alike 🤔, yes I also did this but slightly differently. I copied the Golcar system:- but on my builders recommendation changed it a little. The DPC being above floor level indoors led on a previous build of his led to a crack in the plaster ( slip plane) so we lowered the DPC To internal floor level, the outside level was then below ground slightly but within a french drain so the weep vents could work, we then installed a second DPC in the outside brick skin level with the internal one which was above the outside ground level. 

 

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Yes now on that sketch imagine a vented floorspace inside. Just wouldn't perform as well with cold air and cold bridge of conc beams. If you brought eps up inside and also used something like hanson jet floor that would seem to get rid of the bridges.

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11 hours ago, jpinthehouse said:

Hi

100mm block work 50mm cavity and 140mm stud sitting (as it stands)  165mm of block make up which sit on beam floor which in turn sits on trench blocks 

Hope this makes sense 

 

In that case I'd do a variation on the touchwood method...

 

http://www.touchwoodhomes.co.uk/index.php/foundation-systems/53-strip-foundations

 

Basically a cavity foundation with the beam and block set as low as you can.

 

Slab of insulation above this and carry the cavity insulation right up to sole plate if possible.

 

If we upsized to a 300mm stud I'd have done exactly the same as the diagram but you can modify it support your brick outer leaf which we don't have. 

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