Concrete floor insulation retrofit - cold floor

[gambo]

I've done some reading but still I'm not sure what to do. Late 80s house, 12sqm room (garage conversion from 90s). Based on how cold the floor is comparing to the rest of the house it's likely there is no insulation at all. Given the room is already a bit claustrophobic I don't want to loose more than 10mm of the rooms height (which is how it will likely go up when I replace carpet with engineered wood. The room itself can be insulated in a number of ways like IWI or EWI for the wall with garage and the temperature of the room is not an issue. The issue is just the cold feeling of the floor when sitting.

What's the best way to approach it? Is it doable to remove 20-40mm of the concrete floor to make space for XPS? What sort of cost could it be to do it properly (full retrofit)? Even if I go for full retrofit I'm worried I'll end up doing it myself due to lack of trusted tradesman.

[JohnMo]

Just buy really good high tog underlay and carpet.

 

Trying to

27 minutes ago, gambo said:

remove 20-40mm of the concrete floor

Is just too much like hard work.

 

Engineered wood will not help the cold feel compared to decent carpet and underlay - something like this

https://www.carpet-underlay-shop.co.uk/collections/wool-felt-underlay/products/56oz-heat-insulation-wool-carpet-underlay

 

Don't go with anything that says reflective as reflection doesn't work in close proximity to the carpet, it needs an airspace - regardless of what they claim.

[Redbeard]

30 minutes ago, gambo said:

(garage conversion from 90s). Based on how cold the floor is comparing to the rest of the house it's likely there is no insulation at all.

 

Extremely likely, but...

 

It is/was common to have a step down into the garage so that heavier-than-air fumes wouldn't automatically creep through to the house. If that were originally the case, and the floor levels are now equal, there's either (say) 150mm of concrete/fill there or perhaps a little insulation too (@JohnMo has just posted as I type so sorry if there's any repetition).

[Nickfromwales]

Last GC I did we simply self levelled the original concrete slab to get it flat and level, and then put 2 layers of PIR insulation down over a DPM. DPM needs to be done neatly and tidily with the joints / corners tucked in and taped so the insulation lays perfectly flat. Cut the insulation about 20mm too small to create a gap all around the perimeter for foam, and use the P5 boards (before laying them) as ballast to weigh the insulation down while the foam cures around the perimeter. 

 

Over that went 2 layers of 22mm P5, 1st layer parallel, and 2nd layer perpendicular with both screwed together and just glued joints. 

 

Worked a treat, including an en-suite with a shower tray on legs and a WC, all with zero movement, so no need for screed etc afaic unless you want wet UFH?

 

That won't be cold, but you can get low temp electric UFH kits for use with engineered flooring if you want a bit of extra comfort for the 3-4 months of winter.

 

EWI is only any good if you've dealt with the cavities and draughts, otherwise just do a minimal IWI so all of your room interior is an insulated surface.

[Redbeard]

...However it's cold whatever, so I would suggest you excavate the entire floor and do a good (250-300 EPS or 150 PIR) job of it. Have an upstand of insulation all round the perimeter too.

Edit: @Nickfromwales post had not popped up till after I had pressed 'go'

Edited Wednesday at 15:09 by Redbeard

[gambo]

The rest of the house is fine and I removed part of the carpet and underlay, and just for testing put 25mm PIR + engineered wood under my desk. I can see that 25mm already makes it much better. GIven it's garage conversion and potentially deep concrete, is there an option to remove 20-30mm of it just to ad XPS? Anyone knows of a company in SW to do such retrofit?

[Nickfromwales]

10 minutes ago, gambo said:

The rest of the house is fine and I removed part of the carpet and underlay, and just for testing put 25mm PIR + engineered wood under my desk. I can see that 25mm already makes it much better. Given it's garage conversion and potentially deep concrete, is there an option to remove 20-30mm of it just to ad XPS? Anyone knows of a company in SW to do such retrofit?

If its a deep concrete garage slab then is there still the obligatory 100mm step down into the garage from where you've knocked through?

[Redbeard]

You mention a try-out with PIR, but then actually 'doing it' with XPS. Can I ask why?

 

And can you, as @Nickfromwales asks, confirm whether the floors are currently level from the 'main house' to the garage conversion?

[gambo]

25 minutes ago, Redbeard said:

You mention a try-out with PIR, but then actually 'doing it' with XPS. Can I ask why?

 

And can you, as @Nickfromwales asks, confirm whether the floors are currently level from the 'main house' to the garage conversion?

Mix up, I thought XPS was better but I've just checked that PIR has better parameters.

I measured and the floor in the room is at least 150-200mm higher than garage floor and level with rest of the house.

[Redbeard]

1 hour ago, gambo said:

I measured and the floor in the room is at least 150-200mm higher than garage floor and level with rest of the house.

 

Do you mean there is some of the original garage remaining, with its original floor in?

[Nickfromwales]

2 hours ago, gambo said:

I measured and the floor in the room is at least 150-200mm higher than garage floor and level with rest of the house.

Can you try that one again, plz, lol. Not clear at all what you mean there sorry!!  

[gambo]

Floor of the room converted from garage is level with the rest of the house.

The difference between floor of the house (and that room) and garage floor (it used to be double garage so still one garage left) is around 200mm (+/-50mm).

Hope that makes sense.

[Nickfromwales]

2 minutes ago, gambo said:

Floor of the room converted from garage is level with the rest of the house.

The difference between floor of the house (and that room) and garage floor (it used to be double garage so still one garage left) is around 200mm (+/-50mm).

Hope that makes sense.

Ok, thanks. So what was used to lift the original garage floor up to get it level to the house floor? 

[gambo]

No idea, we bought the house a few years ago. Neighbours say the conversion was done during the build but LA has no record of it. By the look of how it's done (eg.heating pipe running around sockets) it must have been done very unofficially.

[saveasteading]

Getting building regulations would need lots of floor insulation. 

 

If only for comfort then just a layer of tile insulation for foot feeling will make a noticeable difference.

Carpet and slippers complete this logic.

 

There will be energy lost through the floor, but compare to thr cost and mess of rebuilding?

[gambo]

I know it's not worth when comparing to energy savings but there are a few factors:

We have to remove carpets and do something like engineered wood, I don't want to loose more than 10-20mm height, the cold feeling of the floor in colder days is really unpleasant.

I've already have a small corner of the room don using 25mm PIR + engineered wood on top (nothing in between) and it already feels a bit claustrophobic.

[Nickfromwales]

1 hour ago, gambo said:

No idea, we bought the house a few years ago. Neighbours say the conversion was done during the build but LA has no record of it. By the look of how it's done (eg. heating pipe running around sockets) it must have been done very unofficially.

Ouch.

 

My biggest worry would be about the bund between the useable garage and the 'new' residential half of the garage, as that's supposed to prevent fuel spills from interfering with the habitable part of the home (hence the step down from the existing house into the garage)....

 

Also, I'd be worried that fire regs weren't observed and the plasterboard etc creating the dividing wall was (is) insufficient to provide a fire barrier in the unpleasant event of a fire.

 

Sorry to pee on your chips btw, but at the very least I'd be sure to fit a 30 minute fire door where you enter the converted bit from the house. Insurance claims may be a bit interesting too, if none of the conversion is kosher / recognised / has BR approvals...  

 

The estate agents / surveyors should have flagged this surely?

[gambo]

We don't keep cars/motorcycles vehicles in the garage so fuel spills should not be a problem.

The issue was flagged by surveyors but we accepted it. Question is what should we do now about it? Retrospective application for 30yo garage conversion?

[Nickfromwales]

40 minutes ago, gambo said:

We don't keep cars/motorcycles vehicles in the garage so fuel spills should not be a problem.

The issue was flagged by surveyors but we accepted it. Question is what should we do now about it? Retrospective application for 30yo garage conversion?

Your choice, and yours alone. The property will be valued in the future, less that extra habitable space afaik, so getting this immortalised in proper order may be beneficial for longer term options for higher resale valuations, or may be a can of worms you just can't be arsed to open...

 

If you're happy to continue as-is, then the minimum, as said, would be to change to a fire door and lining. Then you defo should extend the linked (mains powered) heat/smoke detection system out to the garage and put a multi sensor detector in there for early warning (if there's not one there now), and basically treat that arrangement as if it's still just the garage and still a fire risk to the main residence.

 

Back to the original question, we'd need to know what the floor was raised with (assuming they just poured a load of concrete in is a bit too little info to go on of course!), so if you can take up a corner of the room to investigate that would help. You can use a 200mm long drill bit to just drill down slowly until the drill pops out past the slab (if its masonry) and report the findings and the depth that you broke through. Do this at least 300-400mm in from the edge to get an accurate 'reading'.

[gambo]

Apart from the cold floor, how can I fix this room? There will be a lot of mess done in that room so I don't mind redoing some of the work but have no idea what the actual issues are.

Regarding the floor, what am I looking for when drilling?

[Nickfromwales]

15 minutes ago, gambo said:

Apart from the cold floor, how can I fix this room? There will be a lot of mess done in that room so I don't mind redoing some of the work but have no idea what the actual issues are.

Regarding the floor, what am I looking for when drilling?

What is that a pic of? Looks a lot like a wall….?

[gambo]

Yes, thats how the wall of that room looks like inside the garage.

[Nickfromwales]

15 minutes ago, gambo said:

Yes, thats how the wall of that room looks like inside the garage.

That should all be dressed in with 2 layers of FR PB. Defo done off the radar!

[gambo]

There is PB inside but I would be surprised if it was 2 layers or FR.

So, is there any for-dummies description how such conversions should be done?

I get that fire resistance is important so that's something I would rectify. What about floor? If it's just concrete on top of concrete shall I try to skim it and/or put VIP insulation +6mm cement board/plywood + engineered wood?

What can LA say if I go for retrospective permission given it's 30yo?

[JohnMo]

Think you have two options 

1. Rip it all out and do it correctly - may not be easy unlikely to be cheap. Could grow arms and legs, from a planning perspective and construction scope.

2. Do a good thermal underlay and  good carpet. Pretty cheap, a warmer feeling to the floor, very constrained work scope. If you are concerned with damp, you could do a liquid DPM, which is basically epoxy paint, paint one day underlay and carpet the next.

 

Option 2 and move on with my life, would get my vote.