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Postby CHARLIEDELTA » Sun Jun 15, 2008 2:52 am

Hi. Would be gratefull of any help with the following points.

1. I am putting in a concrete floor in a barn. I am going to dig the original mud/stone floor out, but am unsure how far to dig down????. And in what order do i put down the insulation, concrete/sand etc.

2. The area that needs doing is approx 123 feet by 26 feet. As it is quite a large area, do i need to do it in stages.

3. Is it essential to use the steel grid to prevent cracking.

4. Do i need to leave a gap around the edges for expansion. And if so, what goes into the gap when it is dry.

5. I understand the concept of ensuring the damp proof membrane comes up the side and is supposed to meet the d.p.m in the bricks. However it is impossible to do this, due to it being very thick stone, and there is obviously no d.p.m in place. So how do i get around this problem.

6. Last one i promise. ha ha. I have read that is best to put any waste pipes in place before laying the concrete. Is it best to do this, and if so, do i just need the one pipe laying and just link all the other waste water in the barn to this one pipe. Also when the pipe comes through the concrete floor, how do u ensure it is damp proofed.

I know i am asking a lot, but would appreciate any help..........Thanks
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Postby TheDoctor5 » Thu Jan 22, 2009 9:22 am

Last year 64% of the questions asked in our forum were answered within our DIY project pages at The project pages are now separated alphabetically and your answers are accompanied by diagrams and the ability to see, and buy, the tools and/or required to complete your project. Use our search box to look for your answer and save a great deal of time and money!
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Postby elwood » Thu Jan 29, 2009 10:41 pm


1.Dig around .400

Floor make up
.200mm of consolidated stone
.025mm sand
.100 floor insulation (check with building control)
1200 gauge polythene
.100 concrete (check with building control)

Then if required
hot water under floor heating
Floor screed.

2.Yes do 4 equal bays (hit and miss)

3.No not essential as long as slab is ground bearing.

4.The insulation has to go around the edge normally .25mm
upstand to bridge the cold spot (check with building control).

5.Just cut the floor polythene off at floor level and get the walls injected.

6.Lay your drainage pipes on top of the dig shingle bed and surround, then stone over them, also lay any ducting at the same time remembering the water service should normally have .750 cover (frost guard)
Lay one run to each bathroom/kitchen etc, lay the run straight to the point
where solids will be collected and y off as and when for sink waste,shower
traps etc.
Just cut a slit in the floor polythene push the pipe through and tape up.

Hope this helps.

I'm also about to convert a barn do you know at
what point you have to start paying council tax.
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Postby thedoctor » Fri Jan 30, 2009 10:22 am

See the DIY Projects section on Ground Floor Slab construction
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