Using Foamglas (or similar) between steel/masonry bearings (eg padstones or chimney propping)

[lineweight]

There are a few products such as Foamglas Perinsul or Marmox Thermoblock which are intended to be used in situations such as the base of walls, where there needs to be a loadbearing thermal break.

 

In refurb projects I commonly come up against situations where a nominally "warm" (ie, it's inside the insulation layer) steel member needs to come into contact with cold masonry.

 

For example, where the beam needs to sit on a padstone in an existing brick wall, which can't be insulated externally. (Same happens with a party wall with a cold loft space on the other side)

 

Or, when propping the tops of chimney stacks when the chimney breasts have been removed below.

 

In these situations the thermal bridging could be reduced by using a layer of something like foamglass inbetween the steel and the masonry. Such a use doesn't seem to be described in the literature for these products but I am wondering if it's something that anyone has seen done successfully.

 

Or perhaps there is some other product for the job that I'm not aware of.

[Mr Punter]

The Foamglas and Marmox will be no good for the high point loads of beams.  You could use something like Armatherm or Farrat but they are specialist and probably £££.

[Tom]

As Mr Punter says, you need a thermal break material specifically designed for point loads. We've used Armatherm between a (warm) steel and cold pad - but it isn't cheap. 

[lineweight]

Thanks @Mr Punter and @Tom, that makes sense. I actually was just looking at Armatherm and Farrat but they don't illustrate their products used in quite that way either; they all seem to be intended for situations where the material is between elements bolted together.

[Mr Punter]

You might get away with Marmox Thermoblock for the chimney masonry but bear in mind the blocks have small columns of concrete (where they get their strength), so they are much better at reducing thermal bridging across the width than their height.

[lineweight]

On 31/03/2023 at 16:52, Mr Punter said:

You might get away with Marmox Thermoblock for the chimney masonry but bear in mind the blocks have small columns of concrete (where they get their strength), so they are much better at reducing thermal bridging across the width than their height.

Yes, I see, hadn't noticed that's how it works. I had already ruled out these Shoeck blocks for the same reason.

 

https://www.schoeck.com/en-gb/type-m

[Dave Jones]

marmox blocks.

[lineweight]

On 31/03/2023 at 13:25, Tom said:

We've used Armatherm between a (warm) steel and cold pad - but it isn't cheap. 

Do you recall roughly how much it cost?

 

It looks like you have to order directly from Armatherm, is that right? In other words there's not really a standard product that can be bought off the shelf.

[Tom]

 

 

1 hour ago, lineweight said:

Do you recall roughly how much it cost?

 

 

Yes, you have to buy direct from Armatherm it seems - and there was a minimum order of £100. I bought 2x foot square 20mm thick pieces and some washers which came to £100.

Email them with what you need, they came back quickly with a quote IIRC.