Might cinderblock internal walls be load-bearing?

[Derek M]

I need to soundproof a couple of rooms in my first-floor flat (there's only one flat above, but it's split over two levels) and a major part of the problem is the internal cinderblock walls, which are transmitting a lot of sound from the other flats in this block and the adjoining block (I was told that this is called flanking noise).

Covering the walls with clip+channel and Rockwool and two layers of soundproofing plasterboard might fix the problem, but it will make the walls several cm thicker and I'd have to move the doors in the living room and bedroom as there'd be no room for them to open with the thicker walls. So if they're not loadbearing, I'm considering just removing the internal walls between the living room and bedroom and the bedroom and bathroom, and replacing them with stud walls that are acoustically isolated from the structure. I'd still have to soundproof the external and party walls but I'd lose less space that way and could leave the doors where they are.

I know I need to get a proper survey done before removing any walls to make absolutely sure they're not load-bearing, so don't worry, I'm not going to start knocking them down if you say you think they might not be. I'm just curious about whether cinderblock is likely to have been used for load-bearing walls.

The first two photos show the end of the wall between the bedroom and the living room (the bit on the right of the photos is the wall between the bedroom and hall). As you can see, there's a single brick layer on top, with cinderblock underneath.

The third photo shows the exposed edge of the wall between the bedroom and bathroom.

The last photo shows the wall between the hall and kitchen, which I have no intention of doing anything to, but I thought it might be useful as it shows a larger area of uncovered wall structure.

If it's possible that they're not load-bearing, will any structural engineer who's a member of IStructE (Institution of Structural Engineers) or ICE (Institution of Civil Engineers) be able to confirm this for certain, and how much should I expect to pay for them to do this and provide a report that I can use to get permission from the leaseholder (local authority) and building control to remove the walls?

 

[23vc]

Yes they could be taking the weight of joists/more masonry above/both

 

[Derek M]

Yes they could be taking the weight of joists/more masonry above/both

Thanks.

The way these flats are constructed is with concrete slabs between the flats, so my ceiling is just plaster on the concrete, then above the concrete slab there's flooring joists (which may be attached to the walls rather than resting on the concrete) and floorboards. So when people install laminate flooring rather than carpet and don't install any additional soundproofing under and/or above the floorboards, that causes a lot of noise to transmit to the flat below.

I'll have to check how much a structural engineer would charge to confirm whether the walls are load-bearing, as if there's a good chance that they are I don't want to waste a lot of money just to be told that, when that money will be better spent just installing soundproofing. I guess I'll still need to get a structural engineer to confirm that the walls and ceiling can take the extra weight of the plasterboard though.

 

[23vc]

To just get a reasonable idea if they’re load bearing might not need an SE, more someone who can access the top of the entire wall to see what if anything is bearing onto it. I can’t really tell from the pics on my phone screen.
Edit: and any lateral restraint it may be providing to other walls adjacent to it

 

[Derek M]

To just get a reasonable idea if they’re load bearing might not need an SE, more someone who can access the top of the entire wall to see what if anything is bearing onto it. I can’t really tell from the pics on my phone screen.
Edit: and any lateral restraint it may be providing to other walls adjacent to it

OK. The bit in the photos is the only bit where the cinderblock is exposed, so I'd have to remove the plaster along the rest of the top of the wall before anyone could inspect it. Are there any particular ways to do that without risking damaging the cinderblock underneath, or is it just going to be a matter of starting at the corner and working sideways along the wall with a hammer and chisel to remove the plaster?

The attached photos show the other end of the living room wall, next to the balcony door, where you can see the plaster is quite cracked already so it will probably be quite easy to chisel it off from that end. The last photo show the bedroom window looking out onto the balcony, and that external bedroom wall is joined to the wall between the bedroom and living room, but it's also joined to the concrete balcony below and above and to the brick wall on the adjacent block, so the living room wall may not be providing any essential lateral restraint.

 

[23vc]

You’d normally knock holes in the ceiling to check this (or access from floor above) rather than knocking plaster off the wall

 

[Derek M]

You’d normally knock holes in the ceiling to check this (or access from floor above) rather than knocking plaster off the wall

Can't knock holes in the ceiling as its a solid slab of concrete, and the person in the flat above me isn't going to let me rip up their floor.

I took the attached photos a while ago when I took up the floorboard next to the wall (on the living room side), so that's what anyone would see if they could take up the upstairs neighbour's floor. The concrete slab which forms the ceiling of the flat below, and then it looks like the cinderblock wall is built on top of that.

The fact that the joist doesn't reach the wall means that they obviously aren't intended to provide any lateral restraint, so I can remove them when I soundproof the room and replace them with rubber pads that will support plywood sheets in place of the floorboards.

 

[jeds]

The problem is getting access to sufficient parts of the structure to be able to be 100% certain? My advice is try to get a rough idea before you start employing engineers.

Think back to the construction; a concrete slab floor/ceiling was either made off site as a plank or cast in-situ? If it was cast off-site as a plank it probably sits on the external walls and the internal walls would have been built afterwards. This should be obvious from the condition at the tops of the walls. If you find a large gap mucked in with mortar that might indicate building afterwards. You don't necessarily need to expose the top of the whole wall to determine that. Just do a small patch and take it from there.

 

[Derek M]

The attached photo shows the exterior of one of the blocks. You've got the entrance in the middle, then there's two 1-bedroom flats on each side on the ground and 1st floors (one at the front and one at the back), then on the 2nd and 3rd floor you've got 2-bedroom flats split over two levels, with the bedrooms on top and the living room, kitchen, etc. below with a full width balcony. Each block shares a wall with the adjacent block, so there's probably a single concrete slab per floor which spans across both blocks, as indicated by the red line.

The orange box around the first floor flat shows the living room on the left and the bedroom overlooking the balcony on the right, with the party wall to the adjacent block, and that party wall is also probably supporting the concrete slab in the middle.

My photos of the internal wall between the Bedroom and Living room aren't great, but I think they show it must have been built after the concrete slabs were fitted, as it consists of cinderblock with a single layer of brick at the top. The last photo is the wall between the Kitchen and the Hall and it shows the same construction. I don't know that this proves that they're not load-bearing or essential for the stability of the block though, as even if they were built after the main structure was constructed, the architects and engineers will have known they were going to be built before anyone moved in to the flats, and would have taken that into account in their calculations.