Advice needed...Damp Hearth causing floor problem

[demop]

I would really appreciate some advice please.

The house is a 1930's semi detached and the fireplace is unused and bricked up with no sign of dampness on the walls.

The problem is, we have lifted the laminate floor to discover the floor boards surrounding the old hearth are very dark and damp, and the dampness has crept to around 12inch across the boards.

On lifting some of the floorboards it appears that only the joist ends that sit on the hearth are rotten and wet, and the concrete hearth is crumbly in areas.

The chimney breast is on the internal party wall, no back boiler or any pipe work present, there is no standing water underneath and the ground looks ok.

Any advice would be greatly appreciated, does it sound like an expensive specialist job or could a competent DIY tackle it?

Any advice on how to sort this would be great thank You.

 

[vinn]

Photos would help? Above and below floor.

There are four immediate possibilities here:
1. the hearth has a brick fender wall that is infilled with soil - rising damp can come up through the soil.
2. the joisting (or floor boards) thats trimming the hearth is in contact with the soil or the damp brickwork.
3. Condensation under the floor has caused damp wood conditions.
4. the laminate was sitting on a damp surface and it possibly spread the damp out 12"

OP, go under the floor and inspect around the fender wall for the above conditions - note where joist tails sit in wall pockets, & see if the tails are rotted?
Note also that a strong underfloor through ventilation is present.

All redundant flues should be swept & be ventilated top & bottom.

 

[demop]

Here are some pics looking from above, im not able to get under the floor until the weekend to fully inspect and take more pics.

Front of hearth showing dampness on floorboards

Showing damp and rotten end of joist resting on back of the hearth

Thank you for taking the time to reply and offering advice

 

[vinn]

Thanks for the photos.
Photos of the full chimney breast and the room context of the c/b and hearth would also help - pull back all floor coverings etc.

Carefully examine all the way around the c/b and the wall that backs on to it - probe the skirting and flooring.
Best practice would be to at least crack out the concrete hearth, and dig out to below the fender wall level.
It might be that the bricked up fire opening will need opening up and the back hearth removed & dug out.
There has been previous remedial work to the timber - but it was obviously slip-shod & ineffective.
Its probable that some flooring and joisting will have to be cut out & replaced by treated & protected wood.
The nail heads visible in the "new" T&G boards are showing signs of rust from the damp joists below.
Go around the house perimeter & note the location & size of all all air bricks - shine a light through them to see if they are blocked.

If you want to DIY this then we can take you through the process.

Was any of this on the mortgage surveyor's report?

 

[Doggit]

The fact that there is a piece of DPM underneath the floorboards, the previous owners where aware of the problem, and have just covered it back up.

The hearth is drawing up moisture from somewhere, so this first needs sorting out, and then you need to put in new joist ends, and floorboards. You need to lift the floorboards around the hearth to find the extent of the problem. You've very likely going to have to dig the hearth out, rebuild it to the where the joist are going to sit, place a dpm down and then, having cut out the rotted joist ends, add new joist ends to the old joist with bolts, then fill in the rest of the hearth, and then refit new floorboards.

Or get rid of the hearth if it's no longer needed.

It's definitely a competent DIY job, and shouldn't take more than a couple of days.

 

[John D v2.0]

We had almost the same problem, although in our case the hearth was a huge pile of builder's rubbish from the original build, with a thin layer of mortar and tiles on top. The pile was soaking wetfrom water running down the chimney and making all the surrounding joists and floorboards damp.
We shovelled out all the muck and infilled with new joists and a small sleeper wall.
It was simple to diy and we had no experience, so give it a go. In your case you might need a breaker rather than just a shovel.