Internal Walls - Marmox Thermoblocks & Concrete Blocks

[Mulberry View]

I'm thinking of having a go at building my internal walls, there aren't too many of them and I have time on my side.

 

We have a hefty spec Block & Beam floor (175mm beams, all blocks in 215 orientation), with sleeper walls under the internal walls that run perpendicular to the beams and double or triple beams where they don't. The floor was designed for an imposed load of 1.5kN/m2

 

I'm thinking of Marmox Thermoblocks under all the blockwork walls, followed by Medium Dense Concrete blocks up to ceiling height. Doorways built to 905mm.

 

Am I along the right lines?

[Dave Jones]

what do you mean by internal walls, the inside skin or walls built inside the thermal envelope ?

[Mulberry View]

  On 26/09/2024 at 07:26, Dave Jones said:

what do you mean by internal walls, the inside skin or walls built inside the thermal envelope ?

Expand  

 

Room dividing walls.

[Dave Jones]

if they are structural  built off the block and beam yes marmox them for sure.

[Mulberry View]

  On 26/09/2024 at 08:28, Dave Jones said:

if they are structural  built off the block and beam yes marmox them for sure.

Expand  

 

Yes, they are.

[Nick Laslett]

@Mulberry View, please ignore this comment if appropriate, because I really have no idea about a lot of this stuff. I was talking with someone the other day and they said a block wall had poor acoustics. How poor is poor and compared to what, I ask myself. 
 

Anyway, I know you are detailed oriented, so hate to add another parameter to consider, if this is a red herring. I’m sure others will know more. Wall acoustics is such a can of worms. 

[Mulberry View]

  On 26/09/2024 at 09:39, Nick Laslett said:

@Mulberry View, please ignore this comment if appropriate, because I really have no idea about a lot of this stuff. I was talking with someone the other day and they said a block wall had poor acoustics. How poor is poor and compared to what, I ask myself. 
 

Anyway, I know you are detailed oriented, so hate to add another parameter to consider, if this is a red herring. I’m sure others will know more. Wall acoustics is such a can of worms. 

Expand  

 

That's kinda why I want Medium-dense concrete blocks, they're supposed to be a bit better I think. Luckily we don't have much in the way of internal walling in our ground floor.

 

 

I'm keen and always happy to hear all views. It somewhat terrifying attempting this with our Architect having left the project and a number of incomplete details, it's certainly stringing the timeline out.

[Russell griffiths]

Rough opening for doors is too tight, you need to leave room to pack the lining and get it squared up. 
just think you can make a wall as soundproof as you want, but as soon as you put a door in it it becomes pointless. 

Edited September 26, 2024 by Russell griffiths

[crispy_wafer]

build yourself a template for door openings, so you can block up to, and lintel over would be the one thing I took away from watching the brickie on mine (he had a few steel welded ones, but timber would work i'd think!)

[Mulberry View]

  On 26/09/2024 at 09:59, Russell griffiths said:

Rough opening for doors is too tight, you need to leave room to pack the lining and get it squared up. 
just think you can make a wall as soundproof as you want, but as soon as you put a door in it it becomes pointless. 

Expand  

 

What would you suggest for door opening sizes? Also, we aren't decided on internal doors at all yet, do you think the opening size will allow later choice of pre-hung, shadow-gap and so on if we decide to go that way?

[Mulberry View]

  On 26/09/2024 at 10:14, crispy_wafer said:

build yourself a template for door openings, so you can block up to, and lintel over would be the one thing I took away from watching the brickie on mine (he had a few steel welded ones, but timber would work i'd think!)

Expand  

 

Seems like a decent suggestion. I have lots of timber laying around.

[Russell griffiths]

  On 26/09/2024 at 10:25, Mulberry View said:

 

What would you suggest for door opening sizes? Also, we aren't decided on internal doors at all yet, do you think the opening size will allow later choice of pre-hung, shadow-gap and so on if we decide to go that way?

Expand  

You need to work out what you want. 
as a minimum I would go. 
838mm doors 

30mm lining

2mm hinge gap

5-8mm packing. 
 

so 838

+    60

        4

        10

rough opening minimum 912mm. 

[Mulberry View]

  On 26/09/2024 at 11:16, Russell griffiths said:

You need to work out what you want. 
as a minimum I would go. 
838mm doors 

30mm lining

2mm hinge gap

5-8mm packing. 
 

so 838

+    60

        4

        10

rough opening minimum 912mm. 

Expand  

 

That makes sense, I allowed 55mm for a pair of linings as that's what carpenters seem to discuss. I'll shoot for 912mm.

[Mr Punter]

I have used a course of Marmox and medium density blocks.  You could probably get away with swapping the Marmox for a course of 7N aircrete if you want to save some money.

[Mulberry View]

  On 26/09/2024 at 16:45, Mr Punter said:

I have used a course of Marmox and medium density blocks.  You could probably get away with swapping the Marmox for a course of 7N aircrete if you want to save some money.

Expand  

 

That's an interesting idea.

[Russell griffiths]

Don’t forget your height choices 

standard uk doors are 1981

European doors can be 2040. 

[Mulberry View]

  On 26/09/2024 at 19:00, Russell griffiths said:

Don’t forget your height choices 

standard uk doors are 1981

European doors can be 2040. 

Expand  

 

Any pitfall in going 2040? We've got 2500 ceilings.

[Dave Jones]

  On 26/09/2024 at 16:45, Mr Punter said:

I have used a course of Marmox and medium density blocks.  You could probably get away with swapping the Marmox for a course of 7N aircrete if you want to save some money.

Expand  

 

not really, aircrete are massively poorer than marmox.

[Dave Jones]

  On 26/09/2024 at 21:09, Mulberry View said:

 

Any pitfall in going 2040? We've got 2500 ceilings.

Expand  

[Mulberry View]

  On 27/09/2024 at 05:39, Dave Jones said:

Expand  

 

That's very helpful, thank you.

[Mr Punter]

  On 27/09/2024 at 05:37, Dave Jones said:

 

not really, aircrete are massively poorer than marmox.

Expand  

 

I understand aircrete is about three times poorer, but it is 3 times the height, so by the time you are at the top of your insulation / screed layers they are roughly equivalent.

[JohnMo]

  On 27/09/2024 at 08:27, Mr Punter said:

roughly equivalent.

Expand  

That was the way I calculated it all out also.

 

I used engineered brick on top of thermolite, good for fixing too. Our screed is 100mm concrete, so the thermolite block starts above the screed to insulation interface. So the no thermal bridges. All our internal walls are wood stud walls. We left an air gap either side of the acoustic insulation before the plasterboard. 

Edited September 27, 2024 by JohnMo

[DannyT]

  On 26/09/2024 at 11:16, Russell griffiths said:

You need to work out what you want. 
as a minimum I would go. 
838mm doors 

30mm lining

2mm hinge gap

5-8mm packing. 
 

so 838

+    60

        4

        10

rough opening minimum 912mm. 

Expand  

At work we make the door openings 930mm to leave the Chippy happy. That’s for a 838mm door.

lintels are dropped on at 2100mm above finish floor. Again to give plenty of room on the height. Any gap between lintel and door lining is packed with insulation before been plastered over.

2100mm will also leave the decision of going 2040mm or 1981mm until another day.

As mentioned, knock up some dummy frames. 

[Mulberry View]

This has all been very helpful, thanks to everyone who has contributed.

 

Just a couple of points I need to clear up...

 

So, Medium-dense Concrete blocks for the ground floor walls are a good choice?

How high to block up the ground floor walls in terms of the Posi floor above?

[Dave Jones]

  On 27/09/2024 at 08:27, Mr Punter said:

 

I understand aircrete is about three times poorer, but it is 3 times the height, so by the time you are at the top of your insulation / screed layers they are roughly equivalent.

Expand  

 

doesnt work like that.