Info on 1930s living room concrete hearth removal

[swebb99]

Hello there,

I am now working in the rear room of a 1930s house I have purchased and on lifting the laminate floor (replacing with carpet), I have found an old(ish) concrete hearth that was moist/damp to the touch. Obviously I'm concerned about the damp but on inspection the fireplace floor was dry so I suspect the damp is due to a combination of the laminate covering not allowing anything to breath and also the concrete being sat straight on earth/infill which is held in place by a 2ft high surrounding wall under the floor.

Since removing the laminate the concrete has more or less dried out.

Now I don't intend on having a fireplace and I am going to block up the hole. So I thought my options are:

1) Knock out concrete, put in a damp proof layer on top of infill, poor in new concrete, block fireplace and insert vent.

2) Knock out concrete and floor of fireplace, put some new joists in where the new hole is in the floor and put in new floor boards down to cover. Also probably put in a vent from chimney so it can breath in to under the floor so no vent where fireplace used to be.

3) Do nothing other than block fireplace and put in vent and worry about potential damp !

Thoughts

Steve

 

[Nige F]

I went with 2 in my place

 

[John D v2.0]

I went with 2 too!
Given the few hours of work including a trip to the tip, it was worth doing for peace of mind. Same went for the one in the kitchen which was actually rubble with concrete cast on top of a wall plate.

Reason I was extra careful is I was also adding 100mm insulation under the floorboards so this would make damp even more of a risk

 

[Tigercubrider]

Is the damp coming up through the floor or coming down the chimney?

 

[John D v2.0]

Oh yeah good point, ours was coming from above and probably below too! This year we knocked out the whole chimney and replaced the roof, so that's one solution!

 

[swebb99]

I'm going to make a start digging out the concrete tomorrow but I suspect the damp is from the rubble below as all around the hole in the chimney is all dry. The moisture in the rubble is probably rising from ground level or maybe some comes through the wall below the damp course layer.

 

[fidom]

I took out an old tiled hearth in my cottage in Scotland. I was keeping the old wooden fire surround but putting in an inset coal effect electric heater. A mate there deals with thick slate for flooring and he cut me a piece the right size. I mortared that in place and finished the job off with a brass fender.

 

[swebb99]

The hearth is now out and I need to add two new joists to bridge the gap. There was actually no moisture at all in the earth and rubble under the concrete. There were signs of water ingress in the past via the front edge of the chimney but I suspect this has long been fix.

So I suspect the moisture on the top of the hearth when I lifted the laminate was due to the waterproof underlay trapping any moisture at all which will obviously be there because there is two foot of gold humid air constantly flowing under the floor.

I've added a shot but I've done more work since it was took. I've taken the rubble down about 10", knocked half the concrete out from the base in the hole in the chimney and taken out 3 bricks out around the top of the wall that contains the rubble. The idea being the chimney will be able to breath down under the floor and air can also flow over the rubble and keep it and the joists dry.

 

[swebb99]

Sorry meant to update. I've made a bit of progress, hearth dug out and gone down a foot or so, me and the old man have put new joists in and now put new floor boards over the hole. I've stripped the chimney of paper and I'm currently trying to find a plasterer who can take a look at it and sort it out so it is smooth rather than the bumps and lumps it currently has.