Use of ply in stud wall

[chriselevate]

Had a surveyor look at a few rooms upstairs that are being gutted at the moment and he said that some of the internal 65mm block work walls can come out as long as there are some on a 9meter span. Does this sound right?

He’s going to suggest that they are replaced with CLS timber and a 9mm sheet of ply followed by the usual plasterboard.

Hadn’t heard if this before so wondered what you thought before I believe this crazy “magic” he is practicing!

Thanks

 

[Ian H]

It makes the wall stronger. I have it on a structural stud wall in my loft.

 

[SammyInnit]

https://en.wikipedia.org/wiki/Shear_wall

 

[^woody^]

block work walls can come out as long as there are some on a 9meter span. Does this sound right?

Not the way you have written it.

What do you mean - a 9m length of wall or a 9m span of ceiling?
And what are the walls supposed to be doing according to your surveyor?

 

[chriselevate]

I'll try to re-word it.

It's a 9m span of ceiling. The walls I'm talking about are 6mm block sat on a time and then onto my floorboards.
They are just partition walls and are on the first floor only. He didn't like the fact that there is over 9m along this span as he said 9m is the limit.

He wan't to see an acro prop put in, wall out and replaced with CLS studwork and 9mm ply.

Hope that makes a bit more sense

 

[^woody^]

The walls are either load bearing or they are not. If they are not then they can come out.

You may get some adventitious support from any wall, and this may be just to take a little bounce out of a ceiling so that say, when you are mooching around a loft, it does not cause any flexing of plaster and slight cracking. This should not happen if the ceiling is designed as self-supporting, but it's a bit of insurance on long spans. But that does ot explain the use of plyboard to strengthen a non-loadbearing partition, which is not going to do a thing.

 

[chriselevate]

So I'm guessing that he's saying that one of the two walls is taking the roof load.He seems keen that if the 65mm block comes out in both places then one of the replacement walls is constructed with a sheet of ply in it. As this is taking place it's probably worth doing both. As you said, walking around in the loft will be eased by these newly constructed walls.

 

[^woody^]

Well if it is a load bearing wall, then building it is a bit more than screwing a sheet of ply on.

 

[John D v2.0]

maybe the problem is not because it's load bearing, it's because it's an 8 foot high wall with no buttressing over a long distance.
We have the same kind of 2 inch thick walls upstairs and down, and the SE asked for "wind posts" added to the ends once the chimney breast was removed, to stop them bowing and folding in half. However in our case I think it has about 2kN worth of roof load sitting above two of them, hence the concern. But even non load bearing walls "bear" their own load.

 

[chriselevate]

Yes, I think that’s correct. They are partition walls and not load bearing but as they are breaking a 9m plus span the SE has mentioned putting in CLS walls with 9mm ply. Just never heard of it before so wanted to run it past people on here. Thanks.

 

[^woody^]

Internal walls do not provide any buttressing, and particularly if they are timber and built off floor joists.

 

[tony1851]

Internal walls do not provide any buttressing

????

 

[chriselevate]

So currently there is a span of 10m and in between that span are two buttress walls that are built of 65mm block sat on a timber plate and sat on the floorboard/joists. One of the walls is fully in tact whilst the other had gaps cut for the airing cupboard and goodness only knows what else! lol

It sounds like the SE is going to suggest that at least one of the walls must be replaced with a ply constructed stud wall due to the span being greater than 9m. I’ll try to sketch out what I mean so you can see.

 

[tony1851]

Presumably the surveyor is thinking of table 3 in Approved doc. A which limits the unbuttressed length of wall to 9m.
Plywood (or OSB) sheathed studwork would probably be better than 65mm blocks, but the studwork must be securely fixed to the outer wall, floor and ceiling to have any chance of being effective as a shear wall. Fixing it to a suspended timber floor is not ideal, but probably better than nothing under the circumstances.

 

[^woody^]

Presumably the surveyor is thinking of table 3 in Approved doc. A which limits the unbuttressed length of wall to 9m.
Plywood (or OSB) sheathed studwork would probably be better than 65mm blocks, but the studwork must be securely fixed to the outer wall, floor and ceiling to have any chance of being effective as a shear wall. Fixing it to a suspended timber floor is not ideal, but probably better than nothing under the circumstances.

Table 3 is wall thickenesses isn't it?

Anyway no internal wall in any traditionally designed house or low rise building is doing any buttressing .... or needed to do any buttressing. Stabilty comes from the floor/ceiling/roof. That's how it works.