Flooring advice needed....

Hi

We've recently moved into a new house and are busy decorating, we also wanted to upgrade some of the insulation and install underfloor heating in bathrooms and hallway.

One part of the house is a 1980's extension and my intention was to lift the floor, install insulation along with underfloor heating and replace. However, upon lifting the floor in the bathroom I've come across a bemusing situation whereby there appears to be a concrete slab with joists laid over the top of it with various shims to level, the variation from one side of the room to the other is from a 5cm joist to 8cm.

Due to the random levels and spacing of the joists laying insulation would be very difficult.

My thoughts were that I would have to use self levelling compound with maximum variance been 30mm, then lay insulation and underfloor heating.

Due to the depths involved I'm likely only going to be able to lay 20mm insulation - will it be worth it?

Are there any other options?

Thanks

Robert

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The concrete "floor" below the joists appears to have a DPM(blue plastic sheet) correctly in place.

The DPM would indicate that this was a custom poured slab for the extension, and not say, a patio slab etc. that's been utilised as an oversite concrete. But why was it left so low, and unlevel?

no sub-floor ventilation can be seen? Lack of ventilation will eventually lead to fungal damage.

The joists are not fixed or nogged - did the floor squeak?

Was the finished floor actually level both ways but the joists had a 30mm discrepancy to make up the level?

Is the external ground level above or below the concrete "floor"?

Is the original house floor coming into the extension level with the extension finished floor?
Is the house floor solid or suspended?

Given the amateurish joisting (i doubt that BCO was involved) and the original stone exterior wall (they can be difficult to butt up to) then perhaps some outside pics of the extension might help?

Hi

Thanks for your reply, pictures and comments below....

The concrete "floor" below the joists appears to have a DPM(blue plastic sheet) correctly in place.
I believe so.

The DPM would indicate that this was a custom poured slab for the extension, and not say, a patio slab etc. that's been utilised as an oversite concrete. But why was it left so low, and unlevel?
Correct, this is a two story extension of around 120sqm, had planning permission, but we haven't seen building control certificate.

no sub-floor ventilation can be seen? Lack of ventilation will eventually lead to fungal damage.
I can't see any either

The joists are not fixed or nogged - did the floor squeak?
I believe it's the same in all downstairs rooms, but this is the only one I have raised at the moment, they are in fairness perfectly flat and there are no squeaks, they are screwed to the concrete slab as well.

Was the finished floor actually level both ways but the joists had a 30mm discrepancy to make up the level?
Correct, finished ground floor is impressively level in all aspects, but has been achieved through the various height joists.

Is the external ground level above or below the concrete "floor"?
Below, probably by at least a foot.

Is the original house floor coming into the extension level with the extension finished floor?
The level of the existing house (which is essentially one 5m x 5m two storey room built in the 1500's) is about 6 inches above the extension floor.

Is the house floor solid or suspended?
The 1500's part of the house is flagstones laid on dirt I would assume.

Given the amateurish joisting (i doubt that BCO was involved) and the original stone exterior wall (they can be difficult to butt up to) then perhaps some outside pics of the extension might help?
Sure, variety of pics added below.

Underside of raised flooring boards
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Extension to existing floor
View media item 76451
Floor levels in rest of extension
View media item 76452
Internal and external view of pipes exiting bathroom to demonstrate height and external wall covering (it has a 50mm cavity)
View media item 76453
View media item 76454
Thanks

Robert[/quote]

possibilities:

1. Lift all pipework (and any cabling) from below the bathroom floor, and abandon the present plumbing outlets.

Lift all wood and joistings and prepare the concrete surface for a screed.



The concrete surface can be then screeded with sand and cement to an appropriate height for UFH and say, a tiled finished floor.
When finished this floor will be level in line with the threshold in pic 2.

Re-fit all plumbing runs and box them in. A new outlet through the wall.

Any WC outlet, and any doorway leading directly to the exterior might possibly have to be raised - but more detail would be req'd.

2. Perhaps the in-situ joisting could be more firmly clipped to the slab and raised, as above, to an appropriate height for re-laying the wood floor to meet the threshold in pic 2.

The joist bays could be packed with insulation.

Whether UFH could be usefully fitted is a call for an UFH specialist.
All in option 2. would have to be considered on site.

What you do about the other floors? Probably nothing - wait and see.
Hopefully, nothing except dire maintenance will ever done to the old structure.

Shakespeare's birthday yesterday, maybe he once stayed at your's?

Thanks for the advice, option 2 sounds like the most promising.

What if I just insulated between the joists as best as possible and then placed something like the LoPro10 solution on top to reduce the height build up?

Would I have any issues with damp given the slab is insulated and there haven't been any previously?

Robert

ree said:

possibilities:

1. Lift all pipework (and any cabling) from below the bathroom floor, and abandon the present plumbing outlets.

Lift all wood and joistings and prepare the concrete surface for a screed.



The concrete surface can be then screeded with sand and cement to an appropriate height for UFH and say, a tiled finished floor.
When finished this floor will be level in line with the threshold in pic 2.

Re-fit all plumbing runs and box them in. A new outlet through the wall.

Any WC outlet, and any doorway leading directly to the exterior might possibly have to be raised - but more detail would be req'd.

2. Perhaps the in-situ joisting could be more firmly clipped to the slab and raised, as above, to an appropriate height for re-laying the wood floor to meet the threshold in pic 2.

The joist bays could be packed with insulation.

Whether UFH could be usefully fitted is a call for an UFH specialist.
All in option 2. would have to be considered on site.

What you do about the other floors? Probably nothing - wait and see.
Hopefully, nothing except dire maintenance will ever done to the old structure.

Shakespeare's birthday yesterday, maybe he once stayed at your's?

Click to expand...

I know nothing about LoPro10 you would have to send their tech desk the above details and pics.

No, i didn't think damp would be an issue given the height above GL and the DPM and lack of any signs of damp in your pics.

Gather your information and then have a site meeting with the interested parties/party esp. the UFH fitter.

I presume that you have another bathroom, so time is not a desperate issue.

Thanks Ree

Yes, we have another bathroom, will get in-touch with BCO and UFH company and start making some decisions.

Robert

BCO is not necessary.

In the UK we have to make the BCO aware of thermal upgrades to the floor.