Not happy with Building Control advice :( Advice now needed!

[MetManMark]

Evening

A year ago we bought a house that had previously been used as offices. It was in a state.The house was built in 1777 (grade 2 listed) and has suspended wooden floors. Building control needed to sign the house off as it had been previously used as a commercial property. For this we paid the sum of ~£500. The chap that came round basically said that all he was interested in was insulation so he told us that we would have to install loft insulation (there was none) and install celotex under the floorboards. We lifted all 3 reception room floors and installed 70mm celotex as he had suggested (there was about 300mm void under the boards). A few months ago we noticed evidence of dry rot along the hall (solid floor with ancient tiles). The dry rot people came and offered their advice. My wife mentioned about the celotex in the adjacent rooms and they suggested that this was likely to decrease under floor insulation and increase the likelihood of dry rot. A year after installing the celotex we lifted the floorboards and were somewhat depressed to see a lot of dry rot (there hadn't been any 12 months earlier).

We feel as though the advice we had been given bad advice by building control. The dry rot is likely to have been either caused by the celotex or at least exacerbated by it. We intend to get written confirmation from the Dry rot specialists to this effect and try to reclaim some costs from the council. Essentially we intend to ask for the cost of the celotex (£400) the cost of the additional dry rot treatment (~£500) and the cost of replacing the joists & floorboards.

Do you think we have a case? What would you do?

Mark

 

[Gareth Hughes]

You were wrongly advised, in that listed buildings are exempt from the requirements of Part L of the Building Regulations, where complying would unacceptably alter their character or appearance.
However, the function of a local government building inspector is to see that, where the regulations are to be compied with, the requirements are met. It is not part of their function to instruct you how to do this.
I would be surprised if a building inspector actually gave such instructions, though they may have given the appearance of doing so, I'm afraid.

 

[Matt Green]

The dry rot people came and offered their advice. My wife mentioned about the celotex in the adjacent rooms and they suggested that this was likely to decrease under floor insulation [ventilation?-MG] and increase the likelihood of dry rot. A year after installing the celotex we lifted the floorboards and were somewhat depressed to see a lot of dry rot (there hadn't been any 12 months earlier).

We feel as though the advice we had been given bad advice by building control. The dry rot is likely to have been either caused by the celotex or at least exacerbated by it. We intend to get written confirmation from the Dry rot specialists to this effect....

Pictures- a couple of things don't add up. The age of your building suggest an oak construction and dry rot doesn't like oak much.

A lack of ventilation will never cause dry rot. The air in the void can never hold enough water to raise the moisture content of timber, any timber, even cheap pine, to a level sufficient for a dry rot spore to germinate. It can certainly exacerbate an outbreak, but it still needs a water source to start, usually a freshwater source. Don't lose sight of finding out why you have this issue when dealing with the consequences.

Matt

 

[plasticpigeon]

Hello Metmanmark. I think you have the advice of two of the most experienced people on this forum in this thread. However before you panic more and rip anything out, perhaps you could post a couple of pictures. Is the floor void damp at all, if there was no rot a year ago and there is rot now it suggests that there is a source of dampness that wasn't there a year ago. I'd be surprised if the insulation caused that. Are there air bricks front and back of the house and are these still free and unobscured. Also could the celotex be blocking any air passageways that exist on top of any dwarf walls (for example in my house the dwarf walls that the floor joists sit on are actually solid walls not honeycomb, so the air can only flow through the small gaps between the top of the dwarf wall and the floorboards, if this is blocked with insulation the air flow will be almost non existent). If this is the case removing the insulation or making dwarf walls with holes in (knocking some bricks out perhaps??) would restore circulation.

 

[MetManMark]

Hi there
Thanks for the guidance. I know photos would help but the last time I uploaded them it didn't work for some reason. The room is at the front of the house and is about 5m wide - there are 3 air vents. When I lifted the floor a year ago they were completely blocked up with junk so I cleared them. The room behind this is of similar proportions. I think it was probably originally a suspended floor but it had been concreted over. There are also 3 air vents at the back of the house - these too were blocked and had pipes leading through to the front room. This back room had damp issues so I have lifted the concrete floor and intend to reinstate the suspended floor. The ground under the concrete was damp - having lifted the concrete it has dried out massively. Part of the problem is that to the side of the house the ground level is above the floor inside the house. The outside is paved and in the spring I intend to dig it out to create a French drain / culvert and pipe this into a drain. I think this should help. So I guess what I am saying is that there is a bit of an underlying damp problem that people have tried to fix over the years. I am hoping that ventilation by reinstating the suspended floor and doing the French drain this should help somewhat.
Cheers
Mark

 

[Roger H]

Hi Mark.

So, not much by way of through-ventilation under the floor if the rear part of the building has been concreted and the rear vents blocked? As others have said, it seems unlikely cellotex will have increased the risk of rot. Is the rot evident above or underneath the cellotex? If it is under, I think the cellotex may be innocent. I'd be inclined to have used a vapour permeable insulation e.g. rockwool batts - Try again on the photos.

p.s. Just spotted the other thread on this - it's a lively one!

 

[Gervase]

BCOs will often appear to be laying down the law when in fact they're not. The only part of the approved docs that are legally binding are the bits in green print at the front of each section; the rest is advice and interpretation. Unfortunately most BCOs see the whole document as holy writ. If you feel sure of your position and can demonstrate that the window area is smaller than a post-1914 house, or that extra insulation in the ceilings, or thatch, or 600mm rubble-stone walls or the like have significantly improved thermal efficiency over a bog-standard building, it may be worth arguing to have Part L1 assessed on a 'whole house basis', whereby supposed deficiencies in some areas can be offset by improvements in others. This is admissible, although may BCOs are unaware of this.
All of which, sadly, is too late to help in your case, I know.