Wall construction

[Jilly]

On 06/11/2024 at 14:50, Gary Martin said:

the siting of the insulation arbitrary. ??????

Nope, it's not arbitary, it's critical.

[Gary Martin]

Thanks Iceverge

 

my proposal was two skins of normal dense concrete blocks, not soft cavity blocks.

the battens and counter battens would be 25 x50 not 38 x50

the vertical battens would have to be drilled and plugged the horizontal ones 

screwed to the others with 50 mm wood screws. ( vertical cladding)

I agree extra work is required fixing the internal insulation boards, longer screws etc, but time would be saved on not messing around cutting the boards to fit in the cavity, around wall ties etc. Also no chasing out for cables and pipes, plus making good, as with a wet plaster finish.

 

I still want to go cavity block built, not ICF or timber frame.

 

my builder has just sent me pics of a 15 year old TF building that had a failed rainwater downpipe that had been leaking and splashing up under the cladding ,unseen for quite a while. The rot had gone from the sole plate to two verticals . He was brought in for minor alterations and it has progressed to a major refurb.

not his original build by the way.

[Gary Martin]

Jilly I meant arbitrary as in inside the cavity or outside it, in the room.

 

 

[saveasteading]

On 06/11/2024 at 20:57, Russell griffiths said:

rotting at the sole plate is down to poor detail and design, it was a thing in 1980

Was that before the frames had to be supported on a raised brick?

What other poor details were there that have been sorted?

 

Guessing the solutions are from:

Raise on blocks

Tanalised sole plate

Controlled drip

Drain to perimeter

Vapour control has improved.

Ventilation gap.

 

[Gary Martin]

The whole thing was badly designed and built. The exposed glulam ridge beam was rotten on the ends too, In a coastal environment .

 

my point is even a badly built block building can’t rot. Hence my preference for block over timber frame.

[G and J]

Any badly implemented building method can lead to horrendous issues, including masonry inside and out.

 

I believed (as you appear to) that timber frame was the anti-christ when we built our current house.  Been round the block more since then and we’re soon to be building timber frame with part masonry skin, having changed my view completely.  
 

Most important thing is that you are happy with how you are doing it.

[saveasteading]

9 minutes ago, Gary Martin said:

my preference for block over timber frame.

Masonry cracks and crumbles and is heavy.

If the building is well designed and well built then it resists the elements and devourers for a long time.

Hence there are very old timber buildings around, albeit usually of hardwood because that was what was available.

[JohnMo]

11 minutes ago, Gary Martin said:

badly built block building can’t rot

But can have damp, really good heat loss, especially when coupled with poorly installed PIR insulation.  Any badly built building, is just that badly built. Seems a strange preference, you don't want a badly built anything, and accepting you may end that way is poor start to project.

[Iceverge]

On 21/11/2024 at 18:42, Gary Martin said:

my proposal was two skins of normal dense concrete blocks, not soft cavity blocks.

 

Ah ok a terminology difference. 

 

This is "cavity block." They're utter rubbish unless you're building something like garden wall. 

 

 

This is a cavity wall. In this case made from blocks...

 

 

That's ours by the way. 250mm cavity width. Full fill with EPS bonded beads.

 

On 21/11/2024 at 18:42, Gary Martin said:

the battens and counter battens would be 25 x50 not 38 x50

 

Ok I'm getting my head around what you're proposing here. 

 

You'll need battens running up the wall. You can drill and secure them to the blocks. However you'll need to screw into them to take the weigh of the horizontal battens. 

 

If you were to use 2 X "25mm" thick  any more than a 45mm screw would risk any slightly overdriven screws penetrating all the way through and pushing the batten off the wall. (The friction from the vertical battens being tight to the wall gives a lot of strength so you need to avoid this. That means you'd end up with 20mm of the screw penetrating the inner battens. Nowhere near enough in my opinion. 

 

A minimum solution might be 45x45mm battens vertically with 25*75mm battens horizontally. 

 

 

This would allow you to use a 65mm wood screw without risk of over driving it into the blocks with at least 40mm gripping. 

 

These 25*50mm battens are only any good as "spacers" in my view. They will offer very little pull out resistant and split as quickly as you can look at them.

 

 

On 21/11/2024 at 18:42, Gary Martin said:

 

On 21/11/2024 at 18:42, Gary Martin said:

agree extra work is required fixing the internal insulation boards, longer screws etc, but time would be saved on not messing around cutting the boards to fit in the cavity, around wall ties etc. Also no chasing out for cables and pipes, plus making good, as with a wet plaster finish.

 

Anyone who puts rigid PIR boards in a cavity wall is ignorant of the downsides or a moron. I would use full fill mineral wool batts or EPS blown beads instead. 

 

You could still add battens and plasterboard for a service cavity if you wanted to, although chasing and wet plaster is better in my opinion. 

 

 

How would you plan to deal with the thermal bridging from internal walls? 

 

 

Edited November 23 by Iceverge

[Iceverge]

Out of interest of you were to use a timber framed building as I described above you could happily run 25*70mm battens up the walls and 25*75 mm battens horizontally 

 

If you used 90mm collated stainless steel nails the 25mm thick verticals would work ok. There would be 54mm of nail straight into the structural stud which would be plenty. (90mm -25mm batten -11mm OSB.)

 

Similarly I think you'd be ok nailing the horizontal 25*75mm battens too. 

 

90mm stainless nails are 7p. 90mm stainless screws are 24p and take 10 times longer to fit. 

[Iceverge]

On 22/11/2024 at 14:22, saveasteading said:

Was that before the frames had to be supported on a raised brick?

What other poor details were there that have been sorted?

 

Guessing the solutions are from:

Raise on blocks

Tanalised sole plate

Controlled drip

Drain to perimeter

Vapour control has improved.

Ventilation gap.

 

 

Any drawings of this raised brick sole plate. Sounds like a method of fixing one issue by introducing a terrible thermal bridging. 

[Gary Martin]

Iceverge thanks for your answers.

yes I meant a cavity wall made with concrete blocks, (I said I was new to all this).

I take on board your advice re the battens etc. what do you think of initially only minimal fixings for the horizontal battens, then concrete screws in pre drilled holes, going through both vertical and horizontal battens to hold the whole thing together ?
any internal walls will be timber studs so no cold bridging at junctions.

 

for Johnmo, of course I am not aiming or planning or hoping for a bad build, by design or construction and would like perfection. I doubt the other timber framed owners wanted the problems they got either.

[Russell griffiths]

Have you looked into the porotherm clay blocks, used a lot in other European countries, a new build local to me used them. 
they use a thin joint mortar system. 

[Gary Martin]

Not sure if porotherm clay blocks would class as non standard construction or not.

 

easy saleable construction is important to me.

[Russell griffiths]

If you go with your original idea of all the insulation on the inside I’m unsure of where you would position doors and windows, you will end up with very deep external reveals as the windows will need to sit within the insulated area. 

have you not thought of a fairly standard insulated cavity but up the internal insulation for a better u value. 
so 125 cavity or something like with 90 mm cavity boards and 50mm internal, then a service void and then plasterboard. 

[-rick-]

39 minutes ago, Gary Martin said:

Not sure if porotherm clay blocks would class as non standard construction or not.

 

easy saleable construction is important to me.

 

Porotherm is currently top of my list for my build (if I can find a plot for it). I believe it would count as standard blockwork as far as mortgage lenders go (pretty sure I've read that somewhere but you should obviously check).

 

Not sure it makes sense financially though unless you plan to diy. It's supposedly much easier/quicker to lay, but this means that bricklayers aren't keen and you will likely eat a lot of the time savings with the time they take to get up to speed and the higher cost of the blocks. Also questionable whether you'd want to use it on an external rendered wall (manufacturer supports that use but I've seen people here with concerns/issues with that so if I use it I think it'd need either EWI or some form of rainscreen to keep it dry).

[Mr Punter]

15 minutes ago, -rick- said:

Porotherm is currently top of my list for my build (if I can find a plot for it). I believe it would count as standard blockwork as far as mortgage lenders go (pretty sure I've read that somewhere but you should obviously check).

 

In  spite of the name, Porotherm has not thermal insulating properties.  Quite the reverse, as it has hallow voids that allow air to move inside the blocks.  Also a pig to fix to as they shatter.  No fun to cut either.  Sockets, pipes, wires all a pita.  Also you will struggle to find anyone willing to install and may have issues with wall ties and brick coursing.

 

Why is it on the top of your list?

[-rick-]

15 minutes ago, -rick- said:

 

Porotherm is currently top of my list for my build (if I can find a plot for it). I believe it would count as standard blockwork as far as mortgage lenders go (pretty sure I've read that somewhere but you should obviously check).

 

But thinking more. If you are focussed on being a standard construction, then trying to come up with what seems like a novel approach for a new build (50mm cavity then IWI) would seem counter to that. A small uninsulated cavity with IWI is something done to retrofits and is likely a lot of extra work with a lot of compromises.

 

Sticking with a standard cavity construction (though with a wider cavity for extra insulation) would seem like the safest bet.

[Canski]

7 minutes ago, Mr Punter said:

In  spite of the name, Porotherm has not thermal insulating properties.  Quite the reverse, as it has hallow voids that allow air to move inside the blocks.  Also a pig to fix to as they shatter.  No fun to cut either.  Sockets, pipes, wires all a pita.  Also you will struggle to find anyone willing to install and may have issues with wall ties and brick coursing.

The air pockets are the insulation. I have also seen somewhere where the holes in the blocks are filled with what looks like rock wool.

Having said that I have laid 100's of m2 of these in Germany using both thin bed and traditional mortar and I agree with the rest of your comments. A pig to cut and course to openings and penetrations and although I haven't tried them I can imagine that fixing to them is not easy either. Then again most Lidl stores in the UK are built with them .

[-rick-]

1 minute ago, Mr Punter said:

 

In  spite of the name, Porotherm has not thermal insulating properties.  Quite the reverse, as it has hallow voids that allow air to move inside the blocks.  Also a pig to fix to as they shatter.  No fun to cut either.  Sockets, pipes, wires all a pita.  Also you will struggle to find anyone willing to install and may have issues with wall ties and brick coursing.

 

Why is it on the top of your list?

Oh I'm not considering it for thermal properties at all.

 

The main attraction is it's quickly diyable, the blocks are half the weight of concrete, comes supplied with the thinset mortar, you can get a quick applicator and the blocks are easy to cut. It's also much lower embodied carbon than block or brick.

 

There are a good number of downsides too and until I get to the point of serious design on a new place I can't fully weigh them but the points above is why its a focus for when I get there.

 

For context, the flat I currently live in has had problems with both cladding/fire safety and also water ingress. So for anything I do in future, I want to use things that are non-combustable and can survive getting wet.

[-rick-]

I wouldn't want to use without a service cavity for all the sockets etc. The videos I've watched suggest it is easy to cut with the right saw. Why do you say its a pain?

 

As for coursing, I agree, I think it only makes sense if either building a solid wall with large blocks and EWI, or a block/block cavity arrangement with both leaves with porotherm.

[Canski]

18 minutes ago, -rick- said:

The videos I've watched suggest it is easy to cut with the right saw. Why do you say its a pain?

Idon't think videos were available when we used these 🙂 We used saws supplied to us by the German companies. They were similar to a recip saw and I wished I had taken my stihl saws with me but hadn't. The blocks are very fragile if you have cut them in the middle of a line of holes. They were ok using sand and cement because you could fill the holes behind the gaps on the joint but with thin joint this was virtually impossible.

Edited November 27 by Canski

[-rick-]

 

We do seem to be getting quite far away from Gary's topic so maybe should shelve this for now. At some point I'll likely start a new topic on Porotherm as the existing topics seem a bit lacking in some details.

[Gary Martin]

Thanks Rick.

Russell your comments have certainly given me a pause for thought.