As you have just noticed thisgap I suggest you measure it again today.If it's any bigger you should vacatate the room as soon possible as it looks like you're floor is going to collapse at any time!!!!!!!!

Either that or the previous occupants took their laminate flooring & underlay with them

Either take the skirting off and refix touching the floor or fit a nother thin skirting/strip of wood to the front of the ext'g skirting and fill the gap with exp foam.

Jason

[quote author=woodsmith  link=1127933872/0#5 date=1128068575]AK the gap is normally caused by the original builder using wet timber for the floor joists, they are often stored outside and get soaking wet even though they were originally kiln dried (thats the joists not the builder )
As the joist dries out it shrinks taking the whole floor down with it and creating the gap.
It usually blows half a gale underneath making the room impossible to heat.
If you want to remove the skirting, rather than fixing a moulding to the front, I would suggest you buy new skirting an inch or more wider than the existing, that way you will not have to re-decorate. Keith [/quote]Thanks for the reply and the explanation.  I feel that I need to provide more information: The room was a garage before, the access was via an internal connecting door from inside the house, going down a steep (about 10 inch).  

The floor was concret, when the work was done we made the garage part of the house by leveling the garage floor with the house floor by adding concrete.  The floor is as I said a concret floor covered with a carpet.  
The gap I can see is from the lower end of the skirting to the floor (about 1 inch), and than inside the wall, in a way that it looks like the wall is thinner in this area, (all around the room), the gap does not go lower than the floor but inside the wall.  
My question is what materal would be the most suitable, and if I can use ordinary cement would I just feel the gap with it and than plaster or it is more complicated?

BTW, you are right, this room is a cold room.
AK

[quote author=woodsmith  link=1127933872/0#7 date=1128101528]Sorry about that,

The gap is usually caused by timber shrinkage but as you have no timber to shrink then it was either built this way or you may have some structural movement

If you want to just fill the gap then the previous advice is still sound. Dont use sand and cement, you may bridge the damp-proof course. [/quote]

Don't be sorry, you have been very helpfull!

I think that it was built like this, says something about the builder.  
I don't think that this is a structural movement as we reinfoecd the foundations before the work was done, (just to be on the safe side), and the gap all around the room is in the same direction (in to out).
I could maybe find wider skirting but this will not solve the insulation issue, if as you say cement and sand is no good, what can I use to fill the gap, so to have a proper, (as possible), insulation? than I can cover it with the skirting, any how I will have to paint the room, (fixing some plaster cracks)
Thanks, AK

[quote author=woodsmith  link=1127933872/0#9 date=1128114172]If the room is really cold you could lay a floating insulated floor which takes about 41mm off the floor but makes an incredible difference.

Otherwise I would take off the old skirting buy some more, one inch wider, fill the gap with construction foam and immediately refit the skirting. If you are lucky, and the plaster is not damaged as you remove the skirting, you should have little decorating to do. Just run a bead of decorators caulk along the top of the skirting to fill the inevitable gaps. [/quote]
He is taking the piss woodsmith , ,
          He is saying it was a garage be fore now it is room .I doubt if there is a double skin of bricks .Why should there be for a garage ,nowonder it cold

[quote author=splinter  link=1127933872/0#10 date=1128114912]
He is taking the piss woodsmith , ,
          He is saying it was a garage be fore now it is room .I doubt if there is a double skin of bricks .Why should there be for a garage ,nowonder it cold
[/quote]

splinter! you replied twice and both times your reply was very negative and unhelpfull... I think that the one who takes the piss is you...I know whose advice I don't need...

Quote:


Thanks I will try this, it makes sense.

Last question there is always room for one more

I wouldn't use it, mainly because you will need to cut/tear it into small strips then push it into the gap and the the amount of fibres it will shed will irritate eyes as well as lungs. A can of foam should do the whole room for less than £10 not only does it insulate but it also seals the drafts.

One good precaution is to run some wide masking tape round on the carpet to protect it.