Damp? If so possible causes?

CattyUk

...........

FreeBear

The green colouring is verdigris - Typical for a copper pipe that is corroding. It is possible that you have a series of tiny pinholes along the length of the pipe. If you can trace where the pipe goes too/from, it would be worth replacing it. Wrap a bit of pipe lagging round it to keep it away from the subfloor.

There is a possibility that that pipe is for gas, so you must identify where it goes too - If it is a gas pipe, then only a Gas Safe engineer should replace it.

As for the timber rotting - I don't see any evidence of a DPC under them. A few small packers is not enough, and I doubt you have any air flow in the void - This will trap damp air in the space which will condense on the timbers, leading to rot setting in. Might be worth putting a thick layer of Celotex/Kingspan type insulation down and screeding over the top. Depending on the age of the property, this may be a suitable fix. But any work of this nature needs to be done in conjunction with any plumbing repairs - You'd need to make sure the pipe and any cables are accessible and protected from the corrosive nature of cement.

CattyUk

It’s a 60s house fyi

FreeBear

CattyUk said: What I wondered if the old part that needs raising which was garage is like 4 inches lower. Is this enough space to install Dpm/insulation and screed to bring it level?

50mm of Celotex, a DPM, and topped off with 50mm of screed would give you a level floor for not a huge amount of money. The insulation probably wouldn't be thick enough to meet current building regs... To put any more down would involve digging out the concrete and sub-base. That would get expensive very quickly, especially if access is limited and the work needed to be done by hand.

FreeBear

Punching a few numbers in to an online calculator - https://www.changeplan.co.uk/u_value_calculator.php

Target U value for a refurbishment of a ground floor is 0.25 W/m²K

Assume a perimeter of 17m with a floor area of 18m². A slab thickness of 75-100mm.

Putting down 60mm of Polyisocyanurate insulation (Celotex/Kingspan type boards) and topped off with 40mm of screed gives an end value of 0.259 W/m²K - Not quite there, but close enough. As this floor is likely to be considerably less than 25% of the total ground floor, no need to get Building Control involved (that saves yo £300-500 of fees). I certainly wouldn't bother getting BC in to sign off the work... Just don't use polystyrene, as it is has a lower insulating value compared to PUR/PIR foam boards, and also lacks a foil facing which helps to reflect heat back.

Materials cost - Probably around £200. Labour, very much dependent on who does the work.. Shouldn't take more than a couple of days as long as there are no surprises lurking under the timber floor.

Homer_home

You are obsessed with building control 

FreeBear

Homer_home said: You are obsessed with building control 

No.

Building Control is the body that enforces building regs and signs off on work when it is compliant.

Building regulations sets out a minimum standard and "best practice". Non-compliance with building regs could result in enforcement action being taken by the local council.

For smaller jobs around the home, it is well worth paying attention to building regs, and when it comes to insulating, trying to exceed minimum requirements where possible. Complying with building regs does not mean that Building Control has to be involved.

For larger works or anything that involves structural changes, (removal of supporting walls, inserting a new door/window, etc), then Building Control should be involved from an early stage. Failing to do so could adversely impact on the value of the property and make it difficult to sell on top of any enforcement action a council may take.

Homer_home

@freebear even though I wasn't refering to you it's nice to know you're paranoid enough to think I was!

FreeBear

CattyUk said: I simply am trying to ascertain whether I need involvement or not as I don’t want to get into trouble or implications when I sell the house.

As long as you are under 25% of the total ground floor area of the whole property, no need to involve Building Control.