potential pitfalls in removing concrete floor

[c r]

hello all

i have been reading this excellent forum for a long time, but now the time has finally come for my 1st post! sorry if this is a bit long and waffly...

i am restoring my mum's small but cute 2up-2down victorian terraced house in east london, she has only lived here for a few years so i dont know that much about the houses history. we are now the only house on the street with sash windows, and thankfully the house is still pretty much to its lovely orginal design. i do however believe (in my amateurish opinion )that the concrete floor in the scullery/kitchen area, at the back of the house, would not have been original, i think this for two reasons: 1.the concrete floor breaches the dpc by three brick courses. (i can clearly see the dpc cos ive got the floorboards up in the adjoining rear living room). 2. on the one external wall of the kitchen there is an old metal air vent at the bottom of the wall, but when i poke a stick through it i just abruptly get concrete! and the concrete floor is defo not a thin 'screed' over a wooden floor, so cannot see what the vent would be ventilating now

chemical damproofing has clearly in the past taken place in this room, with evidence of an internal sand/cement render and injection holes (quite randomly placed aswell!). mayeb the damproofing worked for a bit, but it is well and truly failing now!. damp is present in this room, on ALL the walls up to a about metre in height from the floor. and the part of the wall in the adjoining room to the kitchen/concrete floor also has similar quite wet damp patches. im no expert but my hunch is that its more than condensation...

so im assuming that the concrete floor is forcing the ground water to the walls, where it rises breaching the dpc, the failed damproofing probably now only making the problem worse...ive read on this forum and elsewhere about damp, until my eyes hurt, and my question is not on damp, but what potential problems could i encounter if i were to remove the concrete floor?? structural issues perhaps? would an infilled concrete floor at present be adding any support to the walls? the bricks below floor level, that i can see from the adjoining room, dont look to be of engineering type quality, some of them are quite crumbly and all are damp to touch. is it possible they could have been weakend through being saturated for some time? is there anything to be weary of when breaking up concrete floors, apart from hidden pipes/cables? things that could go wrong....!

many thanks, apologies if im slow to reply back to anyone- i dont have the net at home

 

[another_richard]

Look outside the front and back and see if there are drains. If so open up and see if the pipes flow into your house. This might allow you to sight where the underlying drains are (if any).

 

[c r]

thank you. yep im 99.9% sure the drains dont run through the concrete. maybe 100% sure would be better though!

i guess to simplyfy my original post im mainly wondering whether i may disturb the brickwork at base of the wall/foundations if i were to break up the concrete floor? is the concrete likely to go right down to the foundations of the wall, from what i can see it looks as if its been laid on ground/earth infil level, am hoping the foundations would be a few courses deeper than this...

 

[middi]

From what you are describing it sounds like a previous serious botch job to me.

Just remove that concrete and see what the heck is going on with that wall and the damp.

Hire yourself an heavy duty hammer drill. You can only be as carefull as you possibly can but I do not think you are in danger of damaging the wall footing.

 

[Me!]

When you start breaking out the floor, start in the middle of the room and not near a wall. Once you have made a hole right through the full depth of the concrete, it becomes much easier to remove the concrete as you can break lumps into the hole. This way you will have minimum force required when you get near the base of the existing walls.

 

[Penners]

You're quite right to be concerned about the depth of the concrete in relation to the depth of the foundations. It would be risky to dig out anything deeper than the foundations (although theoretically the load of the house on the subsoil runs at a 45 degree angle downwards from the bottom of the foundations - but personally I would be reluctant to put this to the test!).

However, it's probably unlikely that whoever replaced the suspended floor with concrete dug out deeper than the foundations. There would seem to be little point in doing so. But the only way you can be sure is to dig down through the concrete and see (in the centre, as suggested by Me!)

Once you've established that the concrete is sufficiently shallow to be safely removable, then the method suggested by Me! sounds good, and would avoid stress on the walls.

Then it's up to you whether you replace the concrete with limecrete, or go for reinstatement of a suspended wood floor (or the latter above the former).

 

[c r]

thanks again

i now have another possibly more serious problem in working out how on earth i tell my mum that i'd like to break up the floor of her beloved kitchen...

 

[Moo]

You just don't mention the possibility of breaking it all up at this stage. All you're doing is making a small exploratory hole that can be refilled leaving barely a mark, aren't you?

 

[Penners]

A nice thought, Moo. But have you ever seen a gentleman armed with a sledgehammer "leaving barely a mark"?

 

[Moo]

That's why the delicate use of hammer and chisel is important in the initial stages.
When the hole's big enough to enable the substrate to be seen clearly, that's the time to involve mama in a serious discussion, in the course of which you paint a terrifying picture of the effect of leaving all the concrete in situ.
Done well, this will have her begging you to get on with it a.s.a.p. She may even hand you the sledgehammer!

 

[plumbers mate]

My mother's victorian terrace in Bishop Auckland had a concrete floor - it was there from at least 1946.
The bath was in the kitchen and the plumbing to/from it ran underneath the concrete.
All the kitchens in the street had concrete floors.
The rest of the house had wooden floors.
The concrete may have been done when the house had the sett-pot water heating system removed and the bath put in. Possibly earth, stone or brick floor before then? Never thought about it till now .
I don't know anything about the street's history - our house was owned by us and most others were owner occupied but some were rented. Could they have all be rented at one time, and the landlord "modernised" them in pre 1935? (when my family moved in)

 

[c r]

that sounds similar to the history of my families house, originally all the properties on the street were owned by the local factory, and rented out. sometime post WW2 i assume the entire street was given a bit of a concrete based 'upgrade' in one go.

from what i can gather, there were originally iron railings at the front of the houses, but these were removed during the war, and so after WW2 at some point, the entire terrace had new front walls built, all the outside ground concreted front and back, with new cement rendered 'skirtings' at the the foot of the exterior walls (breaching the dampcourse...), and whilst they were at it the rear scullery/kitchen and bathroom floor was concreted aswell. like you said, the waste pipes etc in the bathroom all neatly placed within this and it created a nice strong platform for the (new?) bath.

i guess that was the fashion, new houses by then were being built with cement , and i suppose where we are in eastlondon, all the bomb damage around would have meant a need for quick regeneration, so concrete at that moment in general would have seemed and been a good choice?

now however, more or less wherever there has been a cement based addition, weve got damp present. removing the cement rendering at the base of the front wall revealed the dpc, and hey presto, after 2 months or so the front wall is now dry, inside and out, no matter how much it rains!! the bricks and mortar above the dpc are now very satisfyingly dry. so simple, thanks to what ive learnt on this forum.

a few houses on the street have lines of drillholes indicating chemical injection damproofing. my mums house has definately had this in the past, and its inefective now- i cant say how well it would have worked at first. i think the damproofing was done over 15 years ago, so i wonder how long damp has been showing up on the walls- maybe it started soon after those postwar improvements...