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    • CommentAuthorvisitor
    • CommentTimeApr 17th 2009
     
    Hi everyone,

    I need a solution to a problem I have. I have a beam and block floor with about 20-30 cm void beneath it. I would like to fill this void with insulation but I seem to have hard time finding anyone to do it. I have spoken to a manufacturer of poly beads and they reckon it is possible. It is just that I can not find an installer to do the job. I am thinking of buying the beads myself and taking out blocks at regular intervals and fill the void myself. I would prefer to mix the beads with adhesive but I am not sure I would be able to do this without the right equipment.

    Any ideas?

    Cheers,
    Ivan
    • CommentAuthortychwarel
    • CommentTimeApr 17th 2009
     
    does your void have a dpm or over site concrete, if not and you are working on bare soil the insulation will slowly mix with the subsoil and you may well get damp problems.

    also have you looked at perlite very similar to poly beads but made of expanded rock, it is very water resistant and is suitable for such a site. dont bother glueing it.
    • CommentAuthorvisitor
    • CommentTimeApr 17th 2009
     
    Yes there is dpm membrane. I will google perlite. Can I handle it myself?

    Cheers
  1.  
    Hi Ivan. I believe beam and block floors must retain a ventilated void of at least 150mm. You would certainly be required to do this by Building Control if building from new.

    I was once told by a beam manufacturer that this is to protect the beams themselves from absorbing too much moisture [which they may well do if encased in insulation] The result of prolonged moisture is said to be spalling of the concrete cover surrounding the reinforcing bars followed by corrosion and eventual failure. I would look at the specification on a manufacturers certification. Eg BBA Certificate.
    • CommentAuthorvisitor
    • CommentTimeApr 17th 2009
     
    Thanks Paul, perlyte looks very promising for my project. I will use that.

    Mike,

    My house was built on top of a bombed mansion block. The lower-ground (sousterrain?) froor was leveled and used as the base for the house. It is filled with ballast as far I can tell. Building control says he would be happy if structural engineer and manufacturer confirm I can fill the gap and both did. The void at the moment is more than 30 cm at places.

    Cheers,
    Ivan
    • CommentAuthorMike George
    • CommentTimeApr 17th 2009 edited
     
    Ivan, Just to back up what I said. See http://www.bbacerts.co.uk/PDF/2723PS1i1_web.pdf Section 13 It is probably the reason why you cannot get anyone to do it. I'm surprised the manufacturers are going against the standard guidance. In any event the Building Inspector is simply wrong to allow work contrary to good practice and certification. Hope it all goes well for you anyway.
    • CommentAuthortony
    • CommentTimeApr 17th 2009
     
    In my way of thinking you will be fine to fill the void. The technicalities are all wrong, no vapour barrier, no ventilation, etc. If you can talk a bead company into coming and doing it and you sign a disclaimer the do it.

    The reason I think that it will work is that the house is warm and so water vapour tends to move away from the warm = no damp.

    This action will become popular and routine even with no dpm within 10 years I predict --- suspended uninsulated floors were a big mistake.
    • CommentAuthorvisitor
    • CommentTimeApr 17th 2009
     
    Mike,
    The reasons cavity wall insulations installers are refusing to do this is because "we need to fill 66% of the volume of the cavities of the whole house", "we can not get the grant", etc etc which are imo excuses that they simply do not understand what needs to be done and are looking for the quick buck of standard jobs.

    After reading about the coated expanded perlite (thanks Paul) I will go with that as it is hydrophobic and water repellent. It is approved as a full-fill insulation. I have taken samples from the "soil" under my floor and it is all sand. It was completely dry even after the rains from the past few days. What had happened I think is that the lower ground floor of the bombed mansion block my house is build onto was filled and leveled.

    There are no gas problems (radon, methane) and I am removing my gas supply so no problem from gasification point of view.

    Tony, if I understand correctly, no void = no need to ventilate. I have a ventilated void between my external wall and the wall of the mansion block next door which I plan to fill with pelite as well. On the thermal imaging I did you can clearly see the bright airbricks there.

    Thanks everyone!
    • CommentAuthorMike George
    • CommentTimeApr 17th 2009 edited
     
    Posted By: tony suspended uninsulated floors were a big mistake.


    Yes but retrofilliing them is a waste of time and money, and there is no guarantee you will fill all of the void. You would need to remove blocks between each and every beam to stand half a chance of success, and then you would have to hope that you do not get any of the other problems discussed in the BBA I linked to. Easier, cheaper and more effective to insulate above and ensure airtightness at the same time.

    Finally there is the practical aspect of this. I've installed this kind of system, and if it was done correctly the blocks will have been grouted with a cement sllurry prior to screeding. I would expect it to be a right sod of a job to crack out and reinstate the blocks.

    Sorry to disagree so strongly Ivan, but I think you are making a big mistake. Thats my twopeneth anyway, good luck with it
    • CommentAuthorvisitor
    • CommentTimeApr 18th 2009
     
    Hi Mike,
    I am planning to "stuff" insulation under the floor from the side. I have about 50 cm strip cut out already as new "goal posts" needed to be installed. I agree that trying to take out blocks will be very difficult. The opening from the side gives me access to half of the floor area which is better than nothing in my book. Cheaper too :)

    Thanks for the constructive discussion.
    • CommentAuthorCWatters
    • CommentTimeApr 18th 2009
     
    Presumably there is a height reason why you can't do what's normally done and put 50-80mm of Celotex and 65mm screed on top of the B&B? floor?
    • CommentAuthorcookie
    • CommentTimeApr 21st 2009
     
    I agree CWatters? its usual to insulate and screed on top.

    If your short of height, you can insulate and lay wood flooring directly on the insulation saving you the thickness of the screed, but probably would need to run a thin screed on top of the block and beam to make it air tight.
    • CommentAuthorvisitor
    • CommentTimeApr 22nd 2009
     
    This is an existing floor which is: beam and block, 50 mm eps, 65 mm screed on top. I want to add further insulation. I can not add it on top of the screed so I am planning to fill the void bellow the beam and block.
    • CommentAuthortony
    • CommentTimeApr 22nd 2009
     
    Let us know how you get on then please.
    • CommentAuthorvisitor
    • CommentTimeApr 22nd 2009
     
    Hmm... This forum is so good. I always get ideas. From another thread I understand that it is not mandatory to have a screed over the insulation of my beam and block floor. Seeing how easy is to cut and remove the screed can I remove it and then install rigid insulation in its place? I am planning to have bamboo flooring installed throughout.
  2.  
    Yes, you could do that. You can get insulation laminated to chipboard flooring which you could use as a sub-base for the bamboo. In theory you could go for something like 100mm PUR laminated without losing any headroom giving a u-value of around 0.2W/m2K
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