Costs of Retro Fit v Dig up and re-screed UFH

[Digger1]

1950's bungalow / house conversion

 

2.5m ceiling Hight

 

Weighing up the pros and cons of adding a slim profile UFH system on top of existing screed against removing old screed, adding insulation and then rescreed.

 

Would costs be similar?

 

Thanks

 

 

[markc]

Unless the existing floor is already well insulated you really need to dig it out and start again

[CotswoldDoItUpper]

Is there any insulation in existing screed? If not and you just add a retrofit system then a lot of the energy will go into heating the slab rather then the room. 
 

Think it’s prob a dig out and start again, which will be much more expensive I assume.

 

good luck!

[Digger1]

I would assume no insulation under existing floor.  

[Dave Jones]

sounds worse than it is, a day with a micro digger with breaker and the old floor will be out. half a day to insulate and dpm then you ready for underfloor and screed.

[Digger1]

Would an alternative be to add 25mm insulation on top of existing screed then add a low profile system (30mm) onto that?

[markc]

11 minutes ago, Digger1 said:

Would an alternative be to add 25mm insulation on top of existing screed then add a low profile system (30mm) onto that?

It is an option if you definitely don’t want to pull the old floor out

[Russell griffiths]

Without 100mm of insulation you are really loosing a lot of heat (cost) downwards. 

[James Newport]

The materials for inscreed Ufh tend to be cheaper than overlay - worth factoring that into your decision

[jayc89]

I dug out our full house (10m x 11m) approx 30 ton came out. It was my first "proper" DIY job so pretty taunting, but as has been said above, it's quite straight forward. 

 

The one "gotcha" that caught me out - I was using a laser level to chalk lines on the wall for where the MOT/Sand/Conc was to be filled to and ended up with low points in the middle of the rooms - if I was to do it again, I'd still use a laser level on my datum point, but grab a broom handle, mark the correct depth on it and use it to spot check various points around the rooms to make sure I'm at the correct level everywhere.

 

I suspect you'd end up with a far better finish if you dig out.

[Onoff]

With even 300mm of EPS under the floor in a passive esque build I seem to recall you still lose like 8% of your heat down through the floor.

 

I've dug out one room so far and built back up with 150mm pir + 25mm eps underneath. With hindsight I'd have dug deeper and put more insulation in.

[Digger1]

Just to add.  The area is 150m2.  I do have access to a micro digger and the property it being rennervated to be resold once completed - Not a forever home so the best energy efficiency isnt necessary and saving costs is preferable.

 

Which method would work out cheaper?

 

The only part i could really do is remove the existing screed with a digger.  Other than that i would employ labour. 

[jayc89]

It kinda becomes a moral decision then. Overlaying UFH on the existing screed is very likely to provide poor performance BUT, I suspect it would be the cheapest option.

[Adsibob]

7 hours ago, Dave Jones said:

sounds worse than it is, a day with a micro digger with breaker and the old floor will be out. half a day to insulate and dpm then you ready for underfloor and screed.

I think that timing is optimistic. To do it properly will take longer.

[Adsibob]

7 minutes ago, Digger1 said:

Just to add.  The area is 150m2.  I do have access to a micro digger and the property it being rennervated to be resold once completed - Not a forever home so the best energy efficiency isnt necessary and saving costs is preferable.

 

Which method would work out cheaper?

 

The only part i could really do is remove the existing screed with a digger.  Other than that i would employ labour. 

Why are you even bothering with UFH then. Install radiators. 

[Mr Punter]

I am not convinced you will get your money back with UFH.  I would go for 50mm PIR with chipboard overlay and rads.

 

To dig it out is quite an undertaking.  150m2 is a large area.  You could end up with 70 tonne of material removed.

[Adsibob]

6 hours ago, Mr Punter said:

I am not convinced you will get your money back with UFH.  I would go for 50mm PIR with chipboard overlay and rads.

 

To dig it out is quite an undertaking.  150m2 is a large area.  You could end up with 70 tonne of material removed.

+1

[Digger1]

18 hours ago, Adsibob said:

Why are you even bothering with UFH then. Install radiators. 

It will be expected in a home with the market price i hope to achieve.  There's also a vaulted entrance hall which would be hard to heat with rads.

[Adsibob]

On 15/10/2021 at 12:02, Digger1 said:

It will be expected in a home with the market price i hope to achieve.  There's also a vaulted entrance hall which would be hard to heat with rads.

Fair enough. I'm probably skewed by the extortionate price per square foot of property where I live. It's so high that whether or not a place has UFH is largely irrelevant. I have mortgaged myself to the hilt for the next 36 years to buy a damp, old, leaky wreck of a place that needs everything doing.

[Onoff]

55 minutes ago, Adsibob said:

a damp, old, leaky wreck of a place that needs everything doing.

 

Sometimes I wish I hadn't found this place or it's predecessor. Before then I just owned "a house" and all houses were nominally equal, just bigger or smaller. Up until then I thought PIR stood for passive infra red. Airtightness was something to do with Tupperware. Then I went and visited a passiv esque house. It was shortly after this that the realisation / depression set in.

 

?

[SteamyTea]

On 14/10/2021 at 17:03, Adsibob said:

Why are you even bothering with UFH then. Install radiators. 

Too right.

Could fit something like this:

 

 

[Nickfromwales]

If this is going to attract big bucks, why ask the question? Dig it out and get on with it !!  
 

On 14/10/2021 at 16:57, jayc89 said:

It kinda becomes a moral decision then.

Agree 100%. 
Also, you’ll need to provide an EPC when selling and if the floor insulation is dire that will still be reflected there and your marketing will suffer. UK public are far more aware of energy ratings and the longer cost subsequence of buying a pig smothered in lipstick, or as we call them “Persimmon Homes”. 
 

Do the job properly, as it sounds like you’re looking to get your money back anyways, just not as much out of the UFH job as you’d like. If it increases the kerb appeal, with no rads etc, which also lends itself to a much more flexible furniture plan, then dig it out, do it properly, and move onto the next job. 
 

Allow a week to excavate, barrow out, and prep properly for insulation and membranes. You’ll need 2 men on 2 powered barrows to keep up with removing the spoil created by one digger.

Allow another week to install insulation, pipes, edge insulation and screed. Screed should be a one day event, so 4 days of prep / UFH. If you need a very good screeder that travels let me know. 
 

Edited October 23, 2021 by Nickfromwales

[SteamyTea]

34 minutes ago, Nickfromwales said:

Allow a week to excavate, barrow out, and prep properly for insulation and membranes. You’ll need 2 men on 2 powered barrows to keep up with removing the spoil created by one digger.

Allow another week to install insulation, pipes, edge insulation and screed. Screed should be a one day event, so 4 days of prep / UFH. If you need a very good screeder that travels let me know. 

@Dave Jones will do it in 2, and fit you a new gas boiler during his tea break.

[Fallingditch]

On 14/10/2021 at 10:29, jayc89 said:

I dug out our full house (10m x 11m) approx 30 ton came out.

 

@jayc89 would that be about 20 cu m?  removing 200mm of existing slab  and spoil from below the slab?  (if my calculations are correct 🙄 ... ) Can I ask how many person days it took?  (Just comparing it with @Nickfromwales estimate of 3 men, two barrows and one digger for removal of 150 sq m to a depth of say, 400mm?)

[Sophiae]

On 14/10/2021 at 10:29, jayc89 said:

I dug out our full house (10m x 11m) approx 30 ton came out. It was my first "proper" DIY job so pretty taunting, but as has been said above, it's quite straight forward. 

 

The one "gotcha" that caught me out - I was using a laser level to chalk lines on the wall for where the MOT/Sand/Conc was to be filled to and ended up with low points in the middle of the rooms - if I was to do it again, I'd still use a laser level on my datum point, but grab a broom handle, mark the correct depth on it and use it to spot check various points around the rooms to make sure I'm at the correct level everywhere.

 

I suspect you'd end up with a far better finish if you dig out.

I know it’s old, but any chance you may have pictures?