Insulation under screed and dampness

paraicc

Hello all,

I'm currently building and am waiting to put floor screed in on the bottom floor. I have aproblem in that the front door is currently only 4.5 inches off the finished raft floor. The installers are able to left the door anothe half inch which will give me 5 inches in total. I have been led to believe that ideally I should have 2 inch insulation and 3 inch screed. I can't have that as I would have no space left for my finished floor. I am thinking about going with 30mm or 35mm kingspan with a 3 inch screed. It should leave me with enough space for a tile. What I would like to know is if 30mm insulation would be ok as I don't have enough space for the 2 inch insultion.

While I am at it - I may as well get another problem off my chest. I have a leak in a bedroom wall underneath a window. We thought the problem was sorted when we patched up the corner of the window on teh external wall. Plenty of rain since ans all was well. Had a look at the wall yesterday afet the heavy rain on Saturday and the wall and floor has a massive damp patch. Total heatbreaker. Any ideas anyone?? The internal wall is plastered and I'll be p***ed off if I have to rip the plaster and dry ling down again.

Thanks in advance
POC

sydthebeat

Firstly, have you no other insulation under the floor???
If not the a minimum of 75mm PUR or PIR will be required to comply with current building regs... 35mm is totally out....
75mm with a 50mm reinforced screed should suffice.....
or consider a product like 'easy screed'

How come the door level is set already...???
have you built off the raft level and forgotten that insulation and screed is required??? Is all the blockwork complete???

paraicc

Thanks for getting back to me. All the house is built up with the windows and front door installed. The door was installed too low - only 4.5 in off the floor of the raft. I have been told that it should have been 6 inches. What I wanted to know was if I should go with thicker insulation and less screed or vice versa. I have been told by builders that they normally go with 3in screed. I'm not familiar with regulations and am just going on the infomration I have got off a number of builders.
POC

sinnerboy

Why don't you raise the door head ? Put as much insulation in as you can.

Damp below window ,-sounds like DPC is defective - did you install DPC to totally "wrap" the conc cill along bottom , and up the three sides ( both end sides and rear side ? ) .

Or
maybe vertical dpc has not been tailed into the cill dpc ?
Or
Has joint where external wall meets flat part of cill , at corner of window frame , been properly filled and / or sealed ?

sesswhat

It may be an option to step or slope the hall floor down to the front door.

Mellor

sinnerboy wrote: »

Why don't you raise the door head ? Put as much insulation in as you can.

This is the best, and possibably only option.
Reduce the door size if required

muffler

Your builder cocked up on this - let him sort it - raise the lintels/door head

ardara1

Was your wall pumped with insulation or partial fill?

bbam

Mellor wrote: »

This is the best, and possibably only option.
Reduce the door size if required

Mellor.. I actually have a similar problem... fault is my own , sub floor is 75mm too high...
I had same idea, to reduce the door height by 50mm to facilitate the insulation.. However my question is, wont this leave the finished floor baove the dpc level in the walls (50mm in my case)?
Until I saw your comment I was going to suffer with less insulation to match the floor to the dpc...
Would this be a problem ??


Cheers
bam

Mellor

bbam wrote: »

Mellor.. I actually have a similar problem... fault is my own , sub floor is 75mm too high...
I had same idea, to reduce the door height by 50mm to facilitate the insulation.. However my question is, wont this leave the finished floor baove the dpc level in the walls (50mm in my case)?
Until I saw your comment I was going to suffer with less insulation to match the floor to the dpc...
Would this be a problem ??


Cheers
bam

The DPC should be 150mm above the external ground level,
with level access it is also the same height above ground floor level.
Your right that raising the internal floor/reducing the door would leave the DPC less than 150mm above the finished floor, but its not a problem as the DPC is in the external leaf. In many older houses the DPC is the same or below the ground floor level.

The only issue that arises from reducing the door and raising the floor is that the level access is removed, which means that the approach must be ramped.

paraicc

Thanks for all the replys to my post. A lot to chew on. The people who installed the door are going to trim about an inch off the door which is teh max that they can take off the door. This will leave me with the fornt door being approx 5.5 inches off the raft level. What I really would like to know is should I go with 50mm insulation as per the norm and make do with having a little less than the 3 inches of screed or vice versa?

Also with the dampness problem. DPC was put in as it should have been but there must be a problem with the vertical dpc - although we checked this exact same spot before and sealed it up at that corner. There is also a vent next to the lintol of this window - I don't think that this could be a problem???

sinnerboy

Get a construction professional to assist

sydthebeat

paraicc wrote: »

Thanks for all the replys to my post. A lot to chew on. The people who installed the door are going to trim about an inch off the door which is teh max that they can take off the door. This will leave me with the fornt door being approx 5.5 inches off the raft level. What I really would like to know is should I go with 50mm insulation as per the norm and make do with having a little less than the 3 inches of screed or vice versa?

Also with the dampness problem. DPC was put in as it should have been but there must be a problem with the vertical dpc - although we checked this exact same spot before and sealed it up at that corner. There is also a vent next to the lintol of this window - I don't think that this could be a problem???

worst case scenario... install a suspended timber floor throughout and insulated between floor joists.....

but i think it will work out fine with 75mm insulation and 50mm ash screed reinforced.....

bbam

Mellor wrote: »

The DPC should be 150mm above the external ground level,
with level access it is also the same height above ground floor level.
Your right that raising the internal floor/reducing the door would leave the DPC less than 150mm above the finished floor, but its not a problem as the DPC is in the external leaf. In many older houses the DPC is the same or below the ground floor level.

The only issue that arises from reducing the door and raising the floor is that the level access is removed, which means that the approach must be ramped.

Hi again... sorry to hog someone else's thread..
I see from the homebond manual that there is a spec for 150mm to DPC outside.
This doen't mean that the dpc on the inner leaf is 150mm above the inner finished floor... From looking at the homebond manual most of the floors finish level with the dpc on the inner leaf....

I am planning on having 75mm of "thermafloor" or such.
The top of this would be level with the inner dpc...
I plan then to have 75-100mm of finished floor above the inner dpc..
Similar to top diagram on page 47 of homebond manual for edge reinforced floors.

Can anyone tell me if this would be a problem???

I also have the radon barrier which in itself should prevent any damp issues
This is one of those things that eeks in the back of the mind..

Thanks again
bam

Mellor

The level of the DPC (strictly speaking its the DPM/radon barrier that acts as a DPC in the internal leaf) in the internal is normally about the same height as the finished floor. The reason for this is because the CPM runs under the slab, and when it gets to the blockwork at the edge it must have ad upstand. This is where the DPM go up and over the first block course to prevent water entering the cavity from passing over the DPM and deflects it externally.
On average, the floor (slab and insul) thickness is about the same as a block so they end up at the same level.

With floor build up becoming thicker today, the finished floor level could easily be over the level of the top of the DPM, and it shouldn't cause any problem. Hope the above is clear, I probably rambled on a bit.

bbam

Thanks again...
I want decent insulation but don't want to compromise the DPC/DPM to end up with damp...

Cheers
bam