Timber floor, Hollow Core, Insulation

J

Johnny Boy

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I will be installing semisolid floor raised 4 inches off the hollowcore upstairs. I have insulated the house very well so hopefully no draughts. Do I need to insulate between the hollowcore and the wood floor or would it be a waste of precious time and money. By the way I am laying the floor on 3/4 inch rough plywood screwed on to 4"x2"
 
how are you raising it 4 inches off the hollowcore slabs??
have you poured a screed over the slabs??
insulation and draughs are not necessarily corelated.... airtightness comes down to standard of build, draughproofing and lack of services puncturing the building envelope.

i would only recommend insulating over the hollowcore slabs if you are trying to thermally break the first floor from the ground floor... i assume the first floor is private bedrooms.. will these be zoned seperately for space heating??
are you bringing the services below the slabs???... in my opinion this is the best practise...... i wouldnt recommend bringing them over the slabs..... if you are, be very careful as to not have services crisscross over each other, ie rad pipes and drainage pipes.....
 
Thanks for reply syd.I have not screed the hollowcore just grouted it also the services rad pipes drains are all above the hollowcore. Never thought of having them underneath to be honest. Is there a fundemental flaw in having drainpipes over the rad pipes? let me know as maybe I could change something. When the house is built thats when I know how to build a house:D
 
the reason its not a good idea to have the service pipes over the slabs is two fold if you are screeding... but since you are not.... anyway, the problems are 1. access to the pipes in case of problems and 2. if the pipes criss cross you wont get a proper screed finish at that point....

so i assume you are basically creating a suspended timber floor over the slabs???? with 100 x 36 joists at 400 (or 600) centres... yes??
personally this would not be my choice as one of the great pluses of a slab floor is the 'solid' feel you get when walking on it... you will be creating a bouncy timber feel..... also theres a risk of creaking.... which you dont get the otherway.....

it may not be possible to change at this stage because there may not be enogh space in the ground floor floor to ceiling height to allow for a suspended ceiling...
 
indeed the ceilings have been plastered ahh maybe the next house I will be building:) I shall do it.
 
Just to give an alternative viewpoint to Sydthebeat's, I think a "suspended" floor over a hollowcore deck is not a bad option, I for one like a "sprung" floor, it's easier to walk on (especially in bare feet) and even if you do have problems with services later it's a lot easier to lift a floor panel (ply or t&g board) than it is to take up a screed or take down part of the ceiling below. Be sure to take lots of photos of your service runs before the floor finish goes down (helps to identify locations later if there are problems) the debate of solid concrete versus suspended timber is a moot one nowadays given that invariably most people put a floating timber floor over concrete as a finish now anyway.
 
Yep been told to take photos Carpenter but should I insulate between the hollowcore and the wood floor or is it overkill. I was just worried that the gap between the hollowcore and the woodfloor about 5 inches would create an cold area. This is just my own thinking which can be suspect in such matters
 
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