Insulated roof panels for side extension

[yjson]

I'm thinking of using insulated roof panels for the single storey side utility extension (10m x 2.8m) (right hand side of the plan). Here's why:

• They're self-spanning, so no need for a rafter structure, and we get more headroom. That matters to us because the bottom of the main house eaves is only 2.4m from the ground.
• Plus, they're a easy to install, perfect for our self build plans

But, we've got some questions:

1. The roof has a soil pipe going through it (check the pic). Is that a problem (leaking or thermal bridging issue)?
2. How do we attach these panels onto the existing house wall?
3. What is the building inspector's stance on using insulated roof panels for a residential side extension?

Any thoughts?

 

[Sachakins]

I think look at the building regs guides.
Question, moving utility room door from kitchen to living room seems illogical, surely the idea of utility room off a kitchen with access is preferable. As utility normally house washing machine, dishwasher freezer etc?

 

[clogs]

perfect material for wall's n roof.....
to fix to a wall all u need is a big wooden batten....100x50mm or buy the proper C purlin.....
U need to think carefully about the roof to wall connection.....
I think a steel frame is best.....easy to make with galv C section.....it's all diff sizes and can be bolted together......
best thing it's very fast assembly and no special tools needed....
Lastly windage can be a problem that needs careful consideration....but ur project looks quite sheltered......
my temp storage cover....the far one is 7mx7m using steel frame, 160mmx 50mm C section purlins at just over 2m centers....
the nearest addition is also steel framed with 125x50mm wooden joists.....
just ripping it to bits to rebuild the new workshop....
the roof panels are 7.5m long and 40mm thick insulation.....just 2 men can lift em.....
the 7x7m roof was assembled in a morning by us two, admitedly we used the forks to get em up there but there was a lot of hand balling to do....

same style but the caravan cover....

glad to see someone NOT using felt.....

 

[yjson]

I think look at the building regs guides.
Question, moving utility room door from kitchen to living room seems illogical, surely the idea of utility room off a kitchen with access is preferable. As utility normally house washing machine, dishwasher freezer etc?

We are actually going to knock down the wall between kitchen and living room. And the new kitchen cabinet will be extended next to the utility door.

 

[Jester129]

I'm with Sachakins on this, seems expensive as well to gain 800mm cupboards. Where's Spock when you need him (logical)?

 

[yjson]

perfect material for wall's n roof.....
to fix to a wall all u need is a big wooden batten....100x50mm or buy the proper C purlin.....
U need to think carefully about the roof to wall connection.....
I think a steel frame is best.....easy to make with galv C section.....it's all diff sizes and can be bolted together......
best thing it's very fast assembly and no special tools needed....
Lastly windage can be a problem that needs careful consideration....but ur project looks quite sheltered......
my temp storage cover....the far one is 7mx7m using steel frame, 160mmx 50mm C section purlins at just over 2m centers....
the nearest addition is also steel framed with 125x50mm wooden joists.....
just ripping it to bits to rebuild the new workshop....
the roof panels are 7.5m long and 40mm thick insulation.....just 2 men can lift em.....
the 7x7m roof was assembled in a morning by us two, admitedly we used the forks to get em up there but there was a lot of hand balling to do....
View attachment 170515

same style but the caravan cover....
View attachment 170516


glad to see someone NOT using felt.....

Yes I got quoted ridiculous amount for a typical felt warm roof construction. That's why I am thinking of self building it myself. Also, I can gain more headroom by simply using the panels instead of having a rafter structure underneath.

I think the suggestions are brilliant. I'll talk about it with the building control.

One idea though, do you think it's possible to trim the existing house rafters (the eaves bits) and put the panels on the existing house brick walls (outer skin)?

 

[Herr Nilsson]

Here’s my tuppence worth:

• SIPs for roof panels might need a crane to manoeuvre into position, so factor in this cost
• You will need to retain access to the existing manhole cover, which can be annoying depending on what kind of floor insulation/build up you are considering. I.e., dpm continuity
• You have 2x over flow pipes that are penetrating the existing outside wall, so these will need to be re-routed, therefore consider how you are going to do this.
• You also might need to re-route what look like broadband cables, so factor in this.
• You have what I assume is a gas meter on the existing outside wall, so I believe you won’t be able to incorporate this into the internal fabric of the new extension for safety reasons, plus your gas company require external access to the meter or is this being rerouted?

 

[yjson]

Here’s my tuppence worth:

• SIPs for roof panels might need a crane to manoeuvre into position, so factor in this cost
• You will need to retain access to the existing manhole cover, which can be annoying depending on what kind of floor insulation/build up you are considering. I.e., dpm continuity
• You have 2x over flow pipes that are penetrating the existing outside wall, so these will need to be re-routed, therefore consider how you are going to do this.
• You also might need to re-route what look like broadband cables, so factor in this.
• You have what I assume is a gas meter on the existing outside wall, so I believe you won’t be able to incorporate this into the internal fabric of the new extension for safety reasons, plus your gas company require external access to the meter or is this being rerouted?

Those comments are extremely useful—thank you!

Panels:
- I believe each 3*1m panel weighs approximately 30 kg, so it should be manageable for us to lift them.

Manhole:
- Fortunately, it's a private drain, allowing us to install a double-sealed manhole cover.
- You're correct; we need to ensure DPM continuity.

Cable & meter box:
- The cable is our electricity armored cable; the meter box is for the isolator, not the gas meter.
- We relocated our electricity meter box to the front gate as part of a three-phase upgrade. The cable runs from the front gate, goes underground, comes up to the isolator inside the meter box pictured, and then extends to the back of the house, reconnecting to the original consumer unit.
- This setup is temporary, with the plan to move the consumer unit to the side extension where the meter box is located, eliminating exposed cables.

Flow pipes:
- That's a good shout!

 

[Herr Nilsson]

Gotcha with electric cables

Panels might only be 30kg but horizontal and 3 metres up in the air they become a bit unwieldy to say the least!
Consider these lifting aids or similar from HSS:-
• Lift Stacker - various
• ‘Genie Lifts - 159kg Lifter/stacker - 3.65m’ [+ extender arms?]
• Genie Super Lift Advantage

1day hire approx £100 - £250

https://www.hss.com/klevuResults?text=genie lifts

 

[yjson]

I'm with Sachakins on this, seems expensive as well to gain 800mm cupboards. Where's Spock when you need him (logical)?

We are gaining probably slight more than 2m length (up to the new door).
Also, it isn't that much more expensive as we are doing the work ourselves.

Any advice on the roof panels would be appreciated as well!

 

[HOJ]

I wouldn't say that the panels cant be used, with appropriate detailing, we have used them on Barn conversions, but that was for planning and aesthetics rather than functionality, my only consideration would be their use in this situation, they will not match the local "vernacular" style which may well cause you a planning issue, as outlined in the:

Permitted development rights for householders- Technical Guidance

"Conditions A.3 Development is permitted by Class A subject to the following conditions-

(a) the materials used in any exterior work (other than materials used in the construction of a conservatory) shall be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse"

 

[HOJ]

Another option would be would be to use a shallow pitch tiled roof to link over the new extension, similar to this:



Did this on a side extension a few years ago, pitch worked out at 15 degrees which was the minimum for the tiles we used.

 

[alex robinson]

We are gaining probably slight more than 2m length (up to the new door).
Also, it isn't that much more expensive as we are doing the work ourselves.

Any advice on the roof panels would be appreciated as well!

Cannot help with regulations, but the panels are pretty easy to handle. The full 7.5m were a pain, but when cut these went up in no time. Just over 4m, about 3m from the front to the ridge beam.

 

[yjson]

I wouldn't say that the panels cant be used, with appropriate detailing, we have used them on Barn conversions, but that was for planning and aesthetics rather than functionality, my only consideration would be their use in this situation, they will not match the local "vernacular" style which may well cause you a planning issue, as outlined in the:

Permitted development rights for householders- Technical Guidance

"Conditions A.3 Development is permitted by Class A subject to the following conditions-

(a) the materials used in any exterior work (other than materials used in the construction of a conservatory) shall be of a similar appearance to those used in the construction of the exterior of the existing dwellinghouse"

Ahh thanks for flagging.

I actually have got lawful certificate approved for this project. It's a flat roof in the plan but I didn't specify the material in the plan. In the worst case scenario, I guess I can simply wrap the insulated roof panels with felt - most houses use felt for their extensions nearby but I do see some house have glass conservatories.

 

[yjson]

Cannot help with regulations, but the panels are pretty easy to handle. The full 7.5m were a pain, but when cut these went up in no time. Just over 4m, about 3m from the front to the ridge beam.View attachment 170574

Yes, I saw a couple of YouTube videos on this managing to install the whole roof in a matter of hours. Also you save a lot of headroom.

 

[yjson]

Another option would be would be to use a shallow pitch tiled roof to link over the new extension, similar to this:

View attachment 170572

Did this on a side extension a few years ago, pitch worked out at 15 degrees which was the minimum for the tiles we used.

I saw this design before unfortunately I have to go for planning route rather than permitted development route (I have lawful certificate already) as the new roof in your design will be higher than the existing eaves.

 

[TomGW]

Yes I got quoted ridiculous amount for a typical felt warm roof construction. That's why I am thinking of self building it myself. Also, I can gain more headroom by simply using the panels instead of having a rafter structure underneath.

I think the suggestions are brilliant. I'll talk about it with the building control.

One idea though, do you think it's possible to trim the existing house rafters (the eaves bits) and put the panels on the existing house brick walls (outer skin

Yes, you can (and should) remove the fascia and soffit and trim the rafter tails to the wall plate height. This will allow you to place new joists at the same height as the existing ceiling in the house.
To be honest, it will be much simpler, even as a self build, to create a conventional flat roof spanning the 2.8m from the existing wall plate to the new, parallel wall.
My recommendation would be to set the joists level, with furring pieces on top to fall outwards, a t&g osb deck and a grp (Flexitec 2000) finish on top. All completely diy-able - I have just done it this time last year (6m x 3m).

 

[yjson]

Yes, you can (and should) remove the fascia and soffit and trim the rafter tails to the wall plate height. This will allow you to place new joists at the same height as the existing ceiling in the house.
To be honest, it will be much simpler, even as a self build, to create a conventional flat roof spanning the 2.8m from the existing wall plate to the new, parallel wall.
My recommendation would be to set the joists level, with furring pieces on top to fall outwards, a t&g osb deck and a grp (Flexitec 2000) finish on top. All completely diy-able - I have just done it this time last year (6m x 3m)

Good to know it's possible. Did you put any insulation on the roof?

I am thinking of trimming the existing rafters to the inner course. Then, hang the roof panels from the outercourse of the existing cavity to the new extension wall.

 

[TomGW]

Good to know it's possible. Did you put any insulation on the roof?

I am thinking of trimming the existing rafters to the inner course. Then, hang the roof panels from the outercourse of the existing cavity to the new extension wall.

I used 250mm joists for the new roof with 200mm rock wool insulation between and 75mm celotex/plasterboard ceiling below. That left a 50mm ventilation gap above the insulation layer.

I’m not clear on how you are intending to support the metal insulated panels. They can span the distance but do need to be attached (screwed down) to the structure. This is normally to either a timber or steel purlin. If you’re considering the insulated panels simply because they are self supporting across the distance of your span you are forgetting about their attachment to your structure.

I am still inclined to think that a conventional, timber flat roof approach will be more straightforward for you. Just strip the bottom of your roof, trim the rafters, set the new joists alongside the existing rafter tails and nail through. Tapered furring pieces on top, osb deck and grp. Job done.
Once the new walls are built and wall plates in position at the same height as the existing house it’s really a straight run. If you could get an experienced joiner to give you 3 or 4 days you should be able to wipe it out. The grp work will need a dry day but is no more than 1 days work to get the first coat on. A second coat can be added the following day or next year or the year after.

 

[yjson]

I used 250mm joists for the new roof with 200mm rock wool insulation between and 75mm celotex/plasterboard ceiling below. That left a 50mm ventilation gap above the insulation layer.

I’m not clear on how you are intending to support the metal insulated panels. They can span the distance but do need to be attached (screwed down) to the structure. This is normally to either a timber or steel purlin. If you’re considering the insulated panels simply because they are self supporting across the distance of your span you are forgetting about their attachment to your structure.

I am still inclined to think that a conventional, timber flat roof approach will be more straightforward for you. Just strip the bottom of your roof, trim the rafters, set the new joists alongside the existing rafter tails and nail through. Tapered furring pieces on top, osb deck and grp. Job done.
Once the new walls are built and wall plates in position at the same height as the existing house it’s really a straight run. If you could get an experienced joiner to give you 3 or 4 days you should be able to wipe it out. The grp work will need a dry day but is no more than 1 days work to get the first coat on. A second coat can be added the following day or next year or the year after.

For the insulated panels, I believe I only need to fasten them to both ends of the wall plates (the new wall and the existing outer course) for structural attachment. I don't think I need to consider anything structural other than these two ends, similar to what they discussed in reply #13.

Considering a conventional timber roof, it seems much more cost-effective if I can handle the entire process myself. Based on rough estimations:

- C24 timber + PIR board + rubber roof (EDPM): £1500-£2000
- Kingspan insulated roof panels (137mm): £3500-£4000

However, I need to factor in the time and my ability. Installing roof panels might take around half a day, whereas a conventional roof could require at least 3/4 days. And roofers are charging crazy amount these days... I got quoted £1000 day rate for a warm roof...

By the way, did you do a lean to (wall) roof? Or did you attach it to the existing wall plate?