Digging up concrete floors

[KayW]

We are currently thinking about removing the concrete floors in our 16c timber framed house and having tried a small test area, are definitely in need of some help. The total floor area is about 90m2 and the concrete is about 15cm deep. We have done a small test area, a square meter, and have found flagstones underneath. They seem in pretty good condition and unharmed by the concrete, which we are told has been down for about 30 years or more. The concrete floor is on several different levels and in most places is half way up the sole plates. We are planning to replace it with a limecrete/glasscrete floor and install ufh. The sole plates are very ropey in places and we are currently having these looked at and replaced in some places (see earlier topic) but the rest of the frame is in good condition.

Any help on the following would be great: -

1. What equipment should we be using? We used an electric kanga hammer (like a big SDS hammer drill) but it was very heavy going - took my hubbie over an hour to do a square meter. We are also worried about the vibrations affecting the timber frame if we use anything bigger. Have read that it may be better to use an angle grinder? Not keen in doing it by hand as the concrete seems a very strong mix and would take a lifetime.

2. How can we protect the flagstones (grey- but not sure what they are made of - we are in a sandstone area but also on the welsh border)- what will do the least damage - the angle grinder or hammer/breaker?

3. Is it likely that the concrete floors are holding the timber frame together and removing them will put its structural integrity at risk- especially where the sole plates are loose/rotten?

Thank you

K
:roll:

 

[inwood]

From experience it helps to create weak points in the concrete. The best way to do this is with a petrol disc cutter which you can hire from most hire centres. Create cuts across the whole concrete area in a chess board pattern (with squares of concrete about 300-400mm square). Make sure you keep the cuts shallow enough not to cut into the flagstones. You can then use your Kango to cut out each sqaure. If the concrete isn't bonded to the flagstones you should be able to follow the lines around each sqaure and break each square out 'fairly' easily.

Alternatively a hydraulic breaker would be easiest but as you say this may create too much vibration.

 

[chuckey]

Its a rotten job but I guess it has to be done. Is there no damp course under the concrete? (sheet of plastic or similar) Did the concrete not adhere to the flagstones? I doubt that you can buy/hire a disc cutter big enough to cut 5 1/2" deep. Also disc cutters are VERY dusty unless water cooled as in a diamond disc. The weakness of concrete is its low tensile strength (comparatively) so the best technique would always to break it away to an open edge.
I wonder if you drilled a series of holes in a line, with as little material as possible between them to synthesize a slot. Whacking in a large chisel (or your kango) into this slot would split off a useful piece of material.
Breakers are fast outdoors because under the concrete, there is soft earth so the material can burst out of the underneath, but if you have flagstones this is the last thing you want.
I like Inwoods idea, very dusty to cut the slots though.
Frank

 

[Feltwell]

If you wanted to get a deep cut and keep the dust down, the only machine I could think of would be a floor saw:-

http://www.hss.com/g/43234/Floor-Track-Saw-Petrol-350mm.html

BUT - these are designed for use outside, and they keep the dust down by using water - whatever you do would be very messy inside. They are very effective, I've used one on a concrete bridge deck. If you didn't want to do it yourself there are plenty of companies out there that specialise in concrete cutting - normally the same ones that advertise diamond drilling services - look under "drilling contractors" on http://www.yell.com

Of course it goes without saying that lots of ventilation would be required, as these are petrol powered!

Take heart by the fact that the first bit of floor you get up will always be the hardest - concrete is strong in compression, weak in tension, so once you've got that first area done breaking the edges into the hole becomes easier. I like Inwoods idea, but if you do the cuts "dry" you really will create a truly horrendous amount of dust.

 

[KayW]

Inwood, Chuckey, Feltwell

Thank you for all the advice. We like the idea of the petrol disc cutter and are off to hire one tomorrow to give it a go. We will try the chessboard and then use the kanga to remove the squares. There is no damp proof membrane and the concrete does not appear to have adhered to the flagstones. They are quite smooth and the ones uncovered have cleaned up well. I can imagine its very dusty but luckily we are not living there and so hopefully with windows and doors open will be okay. At least we can return to our rental for a bath!

Many thanks

K

 

[Feltwell]

Make sure you get yourselves decent dust masks then - not just cheapo ones - you'll need them!

Last time I used a disc cutter was to make 2 vertical cuts in a wall, prior to putting a doorway in. Visibility in the room was down to about 3 foot by the end of the second cut!

 

[joatex]

Chuckey's idea of a series of holes in line then a bolster to break the remaining bridge looks sound and seems much the same as breaking blocks of Carrera marble from the mountain. In that case there would be a free surface for the block to shift outwards.

15cms is a mass of concrete so presumably there is no reinforcing

If you make the series of adjoining holes around a small square and drive a bolster down the sides, the concrete block should come free, then continue breaking the remaining concrete into the freed area. A crowbar inserted into the drilled holes may be sufficient to start the concrete square moving. Jarring of the jack-hammer may shift more than you would wish. Crowbars are ancient but easily controlled and effects wwell under control.

 

[FamilyWiggs]

I would suggest the petrol saw (Stihl saw) method - the saw is great fun!

Make sure you also hire a canary - these petrol saws indoors are not a very safe idea.

You will need LOTS of ventilation and frequent breaks. The danger of CO poisoning is not to be laughed at. (That's Carbon monoxide poisoning as opposed to Conservation Officer poisoning which could be a humorous past-time, I suppose)

I used a Stihl saw outside to cut flags and on occasion forgot to close the front door - the house very quickly filled with 'orrible fumes.

When using the saw, wear steel-capped boots for safety. Drag the saw towards you to cut a shallow groove and then power up and left the saw drag forwards (away from you) in the groove to cut a deeper cut. This way the saw does most of the work and it is physically much easier to control.

Haven't tried concrete, but imagine it will be tough but you should be able to cut 4-5 inches deep with a blade. Go for diamond-tipped blade and makes sure you water cool it with the hosepipe attachment (messy indoors!). The blade will cut much faster, there is less dust and the blade lasts much longer too (ie costs much less when you return it).

Have fun - and pls post some "action" pics. I'm getting quite addicted to PPUK "porn" - loved Nemesis' pics yesterday (of her house/garden!)

 

[KayW]

Thanks for the tips FamilyWiggs will try and take some action pics!

K

 

[Nemesis]

More excavation yesterday evening. That's the easy part. The wall rebuild will be the hard bit.

Then there's the roof to do, the acres of cement to remove... and so much else internally still to do. A fair bit to keep us occupied for the next decade or so (if we are spared... as they say...).

I have to say the latest edition of Photobucket makes posting pics a little easier.

 

[KayW]

Thought it was time for an update. After twelve days of very hard work have finally finished. Not the most exciting of jobs but am weirdly proud of getting through it. Some action shots to follow.

For those with this job ahead of you heres what failed and in the end succeeded and why....

1st - large angle grinder - does cut concrete but overheats quickly and cuts no where near deep enough for the 5" concrete. Takes way too long.

2nd - Electric saw 12" diamond cutting wheel - electric version of stihl saw suggested (the hire store was too worried we would end up overcome with fumes with petrol version as someone in this area died recently with an petrol water pump). As recommended we cut the floor into a chess board pattern and used our kangoo to break off the squares. This worked well but as with the angle grinder overheated often and in the end we only managed an area the size of a pool table in one day. The dust was bad - ok as we dont live there otherwise would not like to be cleaning the house afterwards.

3rd- large electric breaker - we were worried this would vibrate the timber frame too much but it was ok. The concrete was layed in squares and you only vibrate the one you are breaking. Broke the concrete into good large chunks. Nicely brought the concrete away from the plinth walls/sole plates without removing any of the stones. We managed 1/2 a bay per day which was pretty good going.

In summary - hire a big breaker and just be very careful around the edges where you meet stone walls/plinths. Do wear ear deffenders - we did but still are left with ringing ears. The hardest job is when you lug the concrete into a skip/pile for reuse.View attachment 2

 

[KayW]

If anyone is in doubt about digging up there concrete floors I have attached a piccie of the wet sole plate and plinth wall behind the concrete - hopefully its drying out nicely now.

Unfortunately only a few flagstones were in tact underneath the rest had been broken up as a sub base for the concrete. Hope to resuse in the gaden somehow.

Some more piccies

 

[KayW]

Not exciting i know but resulting concrete pile

 

[Nemesis]

Great work! Well done!

 

[MdB]

Not exciting i know but resulting concrete pile

Hey! I've got one of them!

 

[FamilyWiggs]

Fantastic work - and the pics are strangely exciting! PPUK "Porn" rocks!

I think we need a thread to post pics of our spoil heaps! I have one like that too...

 

[DaveBrigg]

Fantastic work - and the pics are strangely exciting! PPUK "Porn" rocks!

So that's what hardcore porn is?

This pile is part of a birds nest dragged out of the fireplace. My youngest son took one look and said 'is there a dragon living up the chimney?'