Garage Conversion - problems

[Mr Jones]

I need some advice please

We are currently experiencing problems with our attached garage conversion into a habitable room which have been on-going now for 3 months

We were advised that a Building Regulations application would be the best way to go and we submitted an application to the Local Council.

The application was accepted and a payment was made to the local council and work commenced

At the front of the house the garage door was removed and the builder dug out the foundations and called the local council Inspector for sign off. No issues reported.

The builder then proceeded to build the front wall and fit the windows. He built a new front wall with a cavity consisting of a 25 mm air gap and 25 mm insulation – this matched the existing stone and block work, where the garage door was previously.

The plasterer who I appointed as Project Manager then plastered all internal walls, he arranged for the electrician to fit the electric sockets as well as a plumber to move pipes as required.

We were advised by both the Builder and the Plasterer there was no need to put any insulation down on the floor other than good underlay and good carpet. We know now this was incorrect advice

The Project Manager did not call out the local council to inspect the work at any of the required stages, nor were any photos taken

At this stage I called the council inspectors in wanting to know whether everything was in order before moving forward with additional internal work

In summary the Inspector advised that

1/ The level of insulation between the internal and external wall should have been 50mm as per the regulations and the builder should have known better

2/ We needed to insulate the floor

3/ We should have appointed an architect and produced detailed plans

I took some advice and then proposed the following to the council in writing

1/ In order to avoid having to take down the wall, would it be possible to install an additional 75mm of Kingspan insulated plasterboard on the internal wall?

2/ We propose to batton most of the floor and install 75mm of insulation on top of the existing concrete. On top of the insulation a visqueen DPC will be installed and then boarded. Because the side door is at the existing floor level then we have proposed to leave the space in front of this this as existing.

I asked the Council to give us an indication as to whether they would accept the above to comply with Building Regulations before we implemented the proposed works – despite several calls, emails and letters the Council are refusing to respond or advise.

When the Council Inspectors visited us they did inform me that they were not an advisory body and we should take advice from our architect – is it really necessary for such a small job to appoint an architect which no doubt would cost up to an additional £1000?

I have since spoken to a couple of local garage conversion specialists both of which were confident they could assist us with the local council however both of these also have been unable to gain a response. Both specialists advised an architect was not really needed

Now 3 months down the line we are stuck – we don’t wish to continue with the work only for the Council to then not to sign it off and then we would have an even bigger issue. Equally we cannot wait forever for the council to advise

Is the architect route really the only option? And would this provide some sort of guarantee? Can anyone advise best way forward?

Thanks

 

[freddiemercurystwin]

What a pickle, this is what happens when a numpty is employed or when little research is carried out beforehand and it is assumed that the builder knows what he is doing. Hindsight eh?

If the insulation in the wall is Kingspan or Celotex then I would have expected 25mm insulated plasterboard would be adequate on the walls. Or was it just polystyrene?

Can you clarify what you intend doing with the floor? Cos’ it’s not very clear to me including the bit about the side door. Or are you saying you expect to be able to just not bother insulating the bit in front of the door to avoid raising the cill?

Normally there is an existing dpm under the slab unless the house is getting on. What age is the property? In anycase the dpm if necessary would go on top of the existing slab.

 

[Mr Jones]

Yes plenty of lessons learned, plenty of mistakes made here by all, myself included. Even people who come very recommended in the community with references can let you down. And clearly not all builders are familiar with building regulations when you would expect them to be so

The house is 25 years old.

The insulation in the wall at the moment is polystyrene

We intend to batton/insulate/board the garage floor but the issue is the side door. Rather than lifting the side door (additional cost incurred) we propose to leave a square or well just in front of the door at existing level and then have a step up to the new floor. My concern is this square would not be insulated and therefore would this be acceptable?

Thank you for taking the trouble to reply

 

[^woody^]

You don't need an Architect, and you don't need plans. You can get all the details you need from a search on here or in the building section.

Your floor recess idea wont be acceptable, and it will be dangerous.

I would also think twice about lining the internal surface of walls again, to reduce the internal space even further.

Bite the bullet, move the door and open the lined walls and fit the insulation against the external wall. Don't compromise and get a crap job at this stage.

Are you pursuing the project manager and builders for costs?

 

[CambridgeBrummie]

I see no reason to take down the walls you have built. You can offset any lack in the U-value of your walls by improving the U-value somewhere else (eg floor, windows) to end up with the required target heat loss. It is quite common to built walls (similar to existing). I'm surprised the BCO has not suggested this route. Check out Part L1B
http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_L1B_2015.pdf
or get someone to produce a SAP calculation for you based on your proposals (Cost about £150).

 

[^woody^]

You can offset any lack in the U-value of your walls by improving the U-value somewhere else

He can't do that. There are minimum standards for the various elements, and the improvement of them is not unreasonably achievable.

 

[CambridgeBrummie]

He can't do that.

Why not? The new elements just need to comply with the following legislation.

How you do that is then open to debate. The minimum U-values in Section 5, Table 2 are only guides as to what is likely to pass the relevant SAP calculation, it's just more work to demonstrate compliance, but it avoids having to re-build the wall.

 

[^woody^]

Why not? The new elements just need to comply with the following legislation

You can't build an extension with 6mm uninsulated stenni panel walls, and put 2m of insulation in the roof.

 

[russellsmiler]

Can you clarify a couple of things please??
It seems from youre original post you have only introduced a cavity to the front of the garage , what as been done to the side and back??
Usually attached garages (depends on year built) have a floor that is lower than main house usually about 150mm, is this the case with yours??? if so that gives a chance to build up with an insulation, dpm, and screed, although you may need to tank the perimeter internally to appease BC. if this is the case possibly the door and window could be raised. The internal walls should be ok with a overlay of insulated plasterboard, I must admit though the part L regs have been robustly modified, your best bet is to have your inspector out to site, and ideally have a list of proposals that you may of gleaned from here.

 

[Mr Jones]

The rear wall of the garage backs onto the kitchen so that is an internal wall - this has not been touched other than being plastered
The side wall which is external was insulated with plasterboard as this was one of the few requirements delivered by the Inspector at his initial inspection.
Yes currently the floor is lower than the rest of the house and it would make sense when insulating the floor to lift to same level - so we will either need to lift the side door to match the new floor or we will leave a well/square at the side entrance if permitted

 

[russellsmiler]

Right I see.
so it would be wise to lift the floor level to match existing house
a specification for this will depend on what thickness you have to make up, I will assume 150mm
1. 1200 gauge dpm on existing floor lapping up wall at least thickness of floor
2. 100mm rigid insulation , recticel, quintherm, celotex, they all have similar values,
3. vapour barrier, (lightweight membrane.
4. 50mm screed, this may be a pumped superflow type screed that would be installed in hours, you may have to research for people to do this.

The doorway and window!! 1st of will the window now be to low if the floor is raised?? leaving a well for the door would be fine but regulations would dictate!! does the door open in or out? either way you would need a regulatory size level landing either side of the door, this information is readily available online. to tackle the construction of a doorwell i would say you could form the upstand with 1 course of bricks then a timber shutter up the brick face to the required level, leave insulation 100mm short on the inside to allow the screed to thicken and create a solid step. If there is insulation issues by BC (I know they do not offer advice, but they will answer direct questions) then this section could be excavated, insulated and re-cast back to as is prior to forming the well. alternatively you could have the door raised, you may also have to have the sockets raised unless they are ok at the height installed, also am i right in saying then its only the front wall that needs insulatited plasterboard, this need be no greater ( possibly less) than you have already done to the side walls.

Does this help?? it sounds standard stuff that seems quite straightforward to put right.

Russ

 

[noseall]

I can't for the life of me work out why the garage floor was left at the original level and not brought up to the same level as the existing. It would have been a straightforward task to lay down DPM insulation and screed.

I would have been screaming at my customer to raise the floor. Totally baffled.

 

[Mr Jones]

My understanding is that if we lift the floor to the level of the rest of the house the front window which has already been fitted will not need to be lifted - however it would be exactly on the border line (i.e. no room to play with)

The side door opens to the inside - not really enough space to open outwards as only a small alleyway to the boundary dividing fence

Yes there is only a requirement from the council to insulate the already built front wall as external side wall has already been insulated. And there is a requirement to insulate the floor

Thanks to everyone for their advice so far

 

[Mr Jones]

For information I called in a surveyor who reported as follows:-

1. Middle window of 3 has been installed incorrectly (Back to front)
2. Cavity wall has been built incorrectly and does not meet the current building regulations due to the free cavity width being under 50mm and the slim nature of the cavity insulation. (25mm)
3. The existing concrete floor slab has no insulation – currently a cold floor.
4. The existing concrete slab requires a DPM to lap with the DPC within the wall.
5. No cold bridge protection measures to rear of stone mullions.
6. Steel lintel over windows incorrectly installed and currently visible with cold bridge.
7. New opening within existing internal wall has insufficient lintel over.
8. No visible cavity tray DPC or weep-holes to perpends over new window.
9. No visible insulated cavity closers to perimeter of window opening to prevent cold bridge.

To now correct the work we are going to break the internal blocks , rebuild internal leaving wider cavity, lift side door, then skeed the floor up to existing level

 

[Chud]

I hope your former builder/plasterer have PI insurance...