Pin Shack roofing advice/help needed

[Steve C]

Ok last year finally decided that it was time to convert the shed so that I could put a few extra pins in it. Single block built with leaking roof so plan was to fully insulate it and re-roof with either anti condense or insulated roof sheets.

Started well as removed the concrete tiles, roof spars, doors, windows and knocked the front wall down.

As it was only single block have replaced the front wall with double block insulated and fitted dg french doors and window.

All new wood for roof (£££££££££), joiner decided that rather than spars over the blocks, back to front, he would hang it down from the blocks and build a framework for the roof/support with a pan back and front and the sheets on top.

Everything had gone ok up to this point but tbh I wasn't sure about the construction of the roof/frame however thought it would be ok once sheeting was fitted, wrong!!

I told the builder that I wanted insulated roof sheets/anti condense so that there wouldn't be any condensation but as he didn't know a lot about roof sheets he left it to the joiner to organise.

Nice sheets supplied but unfortunately no anti condense strip or insulation on them so of course next morning, after fitting, drip, drip, drip - could nearly have an effing shower in there.

The plan was always to put extra insulation between the roof framework and then board/plaster but didn't solve the condensation, probably made it worse as no air flow/vents.

So job stopped, lots of expensive kingspan falls down daily and no solution yet.

The builder has agreed that the roof panels need to come off and be replaced so my question is to any roofers, tradesperson, excellent diyer's on here. What/how is the best way to rectify/sort this?

Original build



Roof, doors, windows removed



Wall removed



Wall removed



Front wall, dg and roof fitted



Condensation, insulation, etc

 

[PAX]

My advice would be working outside to in:
Roof cladding/rafter with insulation between/vapour barrier/ insulated plasterboard.
You really need a gap between the insulation and roof sheeting (50mm) and fit ventilators at ridge point and eaves
Provided the roof isn't leaking that should work

 

[Paul]

Yup - need at least an inch between the roof and the insulation... so the air can come through the eaves and over the top of the kingspan - lets the Kingspan deal with the warm/cold, which is it supposed to do.

Great job tho!

 

[DRD]

You have my sympathy.

Been there, done it with precisely your problem. Very low pitch roof on a garage, experienced "roofer" fitted these sheets to replace leaking asbestos ones, then a staggering amount of condensation ensued. I was planning to knock the thing down so the roof sheets were just a temporary fix for a couple of years.

Your issue is the sudden temperature change experienced by the thin roofing sheets as the sun rises and sets.

Literally any air at all that is underneath the sheet will cause condensation so you must stop all air "touching" the sheet. Just trapping the air between the sheet and the insulation will not solve your problem. Ventilation will not solve your problem.

Boarding it and putting epdm rubber on is not a good option as this is really a flat roof product. I can think of 3 real world solutions.

1. The ugly bodge. Glue 2x layers of foil backed bubble wrap insulation on the under side. This was adequate for my garage situation as I had thin steel purlins so I could cover 99 per cent of the roof. My wife and I ran beads of cartridge "grab" type glue along each ridge to get a tight fit. Much foul language and sore necks followed.

This is not your answer.

2. Get a spray foam company to spray the underside of your sheets. I have no personal experience of this, but I am told that it works as it eliminates the air gap. The wrong foam or a bad installation might cause the timbers to rot. This is well worth a look though and may well be your best bet.

https://www.evergreenpoweruk.com/spray-foam-roof-insulation-uk/

The one solution I have employed on other buildings and that I know does work robustly .....

3. Buy insulated roofing sheets that are sat in a yard. "Yard stock" is perhaps half of the cost of new stock ordered from a regular supplier.

These sheets have an upper surface of plastic coated galvanised steel, then a sandwich of Kingspan, then a lower surface of nice plastic coated sheet metal. The underside is wipe clean and thus looks "finished" and needs no more decoration in a commercial type environment.

I bought my last lot from these guys. They advertise on ebay and have a Yard in Derbyshire. Delivery is surprisingly expensive if you buy long sheets, I bought 8m ones and it cost £250 plus vat.

https://actionclad.co.uk/

You will need a local tin roof supplier to make edge flashings for you, so just double check they can colour match with the sheet you plan to buy. There are standard colours so they should match 100 per cent - but do ask as Slate for example is becoming a nightmare for some reason and Anthracite seems to be replacing it.

You will then need suitable slash point fixings that tear through the sheet and are designed for wood. If you go for very thick insulation, these wood screws can be surprisingly tricky to find as most folk use metal purlins nowadays. This place has an excellent range and was a life saver for me ...

http://www.roofingsheetsuppliers.co.uk/

 

[AlanJ]

Great space Steve, you’ll be hosting a league meet before you know it! I’m sure you’ll get the roof issue sorted ok.

 

[stoptap]

Would a de-humidifier help ?

 

[DRD]

Today the daily telegraph is reporting that lenders can now refuse to provide mortgages to homes with sprayed roof insulation. It can potentially hide leaking roofs, rotting timbers etc

Probably best avoided ....

 

[Paul]

Today the daily telegraph is reporting that lenders can now refuse to provide mortgages to homes with sprayed roof insulation. It can potentially hide leaking roofs, rotting timbers etc

Probably best avoided ....

And a decently insulated roof wont?? Just another excuse....

 

[Sako-TRG]

Spray foam insulation.
This was on Rip off Britain a few days ago.
A couple had it installed in their loft a few years ago. They then tried to sell their house but the buyer couldn’t get a mortgage after the home report rated the properly worthless.
The sellers had to pay specialist contractors to remove the spray foam at their cost ££££ before they could get it revalued and for the money lender to allow a mortgage on the property.

They reckon the spray foam can trap moisture between the insulation and the supporting joists / beams which can compromise the integrity.

 

[M4carp]

I sold a house in Swindon a couple of years ago that had a massive loft that was totally insulated so you couldn’t see any timbers and the buyers had no issues getting the mortgage. But it wasn’t spray foam it was the insulating bubble foil stuff that someone had fitted/stapled was like a space ship up there
That spray foam is nasty stuff
What if you just board over the spray foam

 

[PAX]

Had that spray foam done on my house in Sheffield about 30 years ago. Utter rubbish, had to be re-done as they missed loads of it and was still really draughty and they made a complete mess. Thought this had been abandoned years ago.
Much better solutions are now available

 

[JMP]

PUR (polyurethane) sprayed foam is also highly combustible and any insurer told of that will get twitchy, often due to a lack of understanding or mis-identification of the type of foam.

Steve, if you decide on composite panels (two sheets of rigid metal with foam between) then avoid second hand EPS (polystyrene) or PUR (polyurethane - same as above) and if PIR (polyisocyanurate - paler yellow colour) get new made by Kingspan as that will mean definately to LPS1181 (fire approved) and will have no issue with an insurer. Even better, is Rockwool cored type but more expensive.

As discussed with you a while back, my old games room outbuilding at previous house that was newly built, had pre-manufactured profile metal sheet with felt type backing to prevent the condensation (air coming into contact with cold surface). FYI Insulation underneath was foil faced PIR to ceiling, not the roof.

 

[Sako-TRG]

Looking at the pictures of the Kingspan brought back some memories for me....

When I was getting my extension built (timber frame)

The joiner was doing a great job measuring and laying the kingspan between the floor joists.
The weather was real crap outside so the builder sent the brick layers and labourers from other sites to help the joiner on my extension.
They started rough cutting the kingspan and nailing it into the rafter / roof joists. They were taking hand measurements FFS!
I waited until they were almost done.
I walked in...

Me - “How’s it going guys”
Tradesman - “Yeah, almost finished for the day”

Me looking up at the inside roof.....

Me - “Call me old fashioned, but isn’t the Kingspan supposed to be butt joined up against the rafter / joists???”

Silence.......

Tradesman - “But we ain’t finished yet, we still have to strap it all together!”

Me - “I may be being silly, how do you strap something together that’s already been cut too short?”

Silence.......

Me - “ Do me a favour guys, pull it down and adhere to the architectural plans, clearly states butt joining kingspan insulation to rafter / joists, I don’t want my heating bills literally going through the roof!!”

I went to work but the Mrs watched them take it down and start again.

Later the joiner apologised to me saying he was new with the company and didn’t want to intervene but was fuming when they started jumping in.

 

[Steve C]

Apologies for my long delay in responding to this thread/advice but have had lots of other things to do and if I'm honest this whole shed debacle has really persisted me off .

I fully understand the principle of insulation, breathable felt, kingspan, ventilation, etc but in this case it doesn't work.

Big thanks to David @DRD for totally understanding and writing a lengthy list of problems/solutions - the bottom line with this type of roof/sheeting is as stated by David

Your issue is the sudden temperature change experienced by the thin roofing sheets as the sun rises and sets.

Literally any air at all that is underneath the sheet will cause condensation so you must stop all air "touching" the sheet. Just trapping the air between the sheet and the insulation will not solve your problem. Ventilation will not solve your problem.

It has taken a long time but hopefully and it is a big BUT, the end is in sight

After having some dick quote me £10k for grp and nearly having a rubber roof/epdm fitted but scuppered by covidinflation - 8x2 osb boards increasing from £15 to £28 and I need x32 of them plus the roof needed some more 6x2/strengthening to fit the boards on.

So hopefully getting some insulated roofing sheets and that should solve the condensation and also save me having to insulate between the rafters as Kingspan has also skyrocketed in price.

The only decision I have to make is do I go for 40mm or 100mm insulation on the sheets as that will be the only insulation on the roof. Don't want to use 100mm if 40mm will do but also don't want to underspec as well. There is quite a substantial price difference, approx £7/800 Your thoughts please.

Couple of pics below of the quality of work by Dick the joiner (not his real name) Forgot to nail this piece of the roof and whenever it rains it runs down the side of the building and most of the insulation has fallen down as well

 

[Steve C]

Great space Steve, you’ll be hosting a league meet before you know it! I’m sure you’ll get the roof issue sorted ok.

Probably need to buy a few more machines

 

[Steve C]

PUR (polyurethane) sprayed foam is also highly combustible and any insurer told of that will get twitchy, often due to a lack of understanding or mis-identification of the type of foam.

Steve, if you decide on composite panels (two sheets of rigid metal with foam between) then avoid second hand EPS (polystyrene) or PUR (polyurethane - same as above) and if PIR (polyisocyanurate - paler yellow colour) get new made by Kingspan as that will mean definately to LPS1181 (fire approved) and will have no issue with an insurer. Even better, is Rockwool cored type but more expensive.

As discussed with you a while back, my old games room outbuilding at previous house that was newly built, had pre-manufactured profile metal sheet with felt type backing to prevent the condensation (air coming into contact with cold surface). FYI Insulation underneath was foil faced PIR to ceiling, not the roof.

Hopefully/finally getting new insulated sheets, either 40mm or 100mm and then no need to insulate between rafters