What support needed for floor under bricked up fireplace?

[AlanJo]

Hi there,

I need some help figuring out how to repair a patch of sinking floor in front of what I presume is bricked up fireplace on the ground floor of our house.

We live in a typical old London 2 bedroom terrace (with the ground floor floorboards raised about 6 inches from the ground). We put in new flooring on top of the floorboards when we moved in 5 years ago (click together engineered wood not laminate as I have written on one of the photos). Recently a patch of floor (90cm x 35cm) against one of the ground floor walls started sinking a couple of inches or so whenever someone stood on it.

I took up what little flooring I could without having a circular saw to see what was underneath and found pieces of a crumbled concrete slab (which is damp and can be broken by hand with a bit of effort) I'm presuming this is a broken up fireplace hearth. I've found one old photo of part of the affected area before we put the floor in and it seems that someone had placed a large wood board over this crumbled concrete which is why we didn't notice it at the time and presumably this board has now also cracked/fallen.

We need to get the patch of sinking floor supported but I'm unsure of what support we would need for the wall? (I'd assume it needs at least a wooden joist? Though there doesn't seem to have been anything at all under the broken up slab). I literally have no idea what/if any support is needed so any advice would be gratefully appreciated.

The photos hopefully give a better idea of what I'm talking about!

Many thanks,

Alan

 

[Adam182]

Hi Alan,

From the photos it looks like the fireplace was bricked up with the first course supported on the Hearth, the hearth has since deteriorated which has caused the slump.

If it were me I would clear out all the loose under the bricks that now look to be hovering, then I would do a bit of hand digging just enough to create a concrete pad the span of the gap, before adding the concrete I would lay down a piece of damp proof membrane in as big of a piece as possible.

Once the concrete had gone off I would brick up the gap to meet the ''hovering wall'' then again once solid fix a decent piece of treated wood to the new bricks running the span of the wall to support the floor that you will then refit.

This is by no means professional advice, I'm just a DIYer.

 

[bobasd]

you seem to have two problems:
1- maybe the joists tails are rotting and givinway to drop the floor.possibly due to lack of ventilation an damp in the joist pockets
2- the hearth an fireplace need openin up.

could be you are in for lifting much or even all of the suspended floor to do a proper job.
when you moved in did the survey point out any damp issues?

 

[AlanJo]

Thank you both for taking the time to reply- it's a big help!

Adam182- That sounds like a really good idea, thank you

bobasd- When we had our survey done the only damp spotted was on the other side of the house (next to the front door), but the cracked concrete does seem damp which is concerning! Am very much hoping the joists are not rotting (the floor is very solid along the outline of the sinking area marked on the photo where I presume the joists run, as far as I can see from what I can currently access there was just no joist or other support under the hearth/front of the wall at all.

I know the best thing to do is just open up a bigger area of the floor to see how damp it is - I was just hoping to have a better idea of what will potentially need to be done before that happens so the floor is open for as short a time as possible (we have a toddler whose main play area is the the lounge so keeping him out of there will be ... stressful)

Thanks both again,
Alan

 

[Adam182]

This is how mine was, I just knocked out the hearth and extended the joist through the void...

 

[AlanJo]

Thank you Adam182 that's a big help to know someone else had the same layout so I know that while not having support under the hearth itself it may have just been normal and is also great to know that you fixed exactly the same issue.
Thanks,
Alan

 

[bobasd]

from your pics you cant yet see whats happenin at the front of the hearth.
boards need lftin to expose the full hearth.

boards also need liftin to expose where the floor sags.wherever in the room that is?

you dont have to have a circular saw to lift T&G boards. just split off the tongue an gently prise the board up. dont go splinterin the boards.
any screwheads revealed just unscrew the screws.

the Adam182 pic above shows a chimney breast with no vent shown. a vent at bottom an top of the redundant flue is needed or you will get salt problems on the decorations at some later date.
redundant flues also need sweeping before blocking off.

 

[AlanJo]

Bobsad- Sorry if I didn't make it clear it's just the area in front of wall where the hearth was that is sagging, and thanks for the advice about the boards- that will be my next step

 

[bobasd]

i dont understand - why not show a large pic of the room showin whats what?