UKH

I thought some of you might be interested in our re-roofing project that we are in the middle of. 

We had a metal roof on a very large, shallow pitched roof. Under that was an old felt and bitumen roof which we think was the original. The roof has leaked the whole time we have been in the house (we moved in a year ago). 

So we started yesterday by taking off the metal, the wooden framework under it. This morning we started by taking off the felt and bitumen layer to see what state the ply boards were in. They were all alarmingly wet. The roof has clearly been leaking constantly and then not really drying. Thankfully, most of the ply boards were ok once they dried off. A few were rotten and needing replaced so we did that. 

The afternoon was spent cleaning the ply deck, sanding the fascia around the edge of the roof and painting it. Then we built a timber edge all around the roof to hold the next layers in place. 

At the end of the day, we started working out the next stage which is laying 50mm of kingspan and then a layer of OSB. We got half a row of that down this evening before we cleared up for the night, mainly to work out what pattern we are doing and get logistics sorted for tomorrow. 

The plan for tomorrow is to get those layers on. We are not really sure how long that will take, but either later tomorrow or on Monday we will prime the roof and then start applying Resitrix rubber roofing. This is new to all of us, we have to heat weld the edges together, which will be an interesting game. I am working again from Monday, so I might not be involved in that bit of the process. 

So that is our adventures for the weekend 😊

Very industrious,  well done!! Great project.

Just a paranoid word of caution,  single ply roofs are great in theory,  but just be so so careful not to damage it. Ideally,  try not to step on it once laid. They are meant to be robust...they aren't,  and finding a leak that's coming from a hole the size of a pinprick is a nightmare!

Take your time with it and get the sequence for access right and you should be fine! 

Resitrix claims to be able to withstand footfall, suitable for fire escapes on roofs. Apparently. 

We won't go walking unnecessarily, but I don't think we need to be too paranoid.

If it's a potential 'forever home', I'd have been tempted to turn it into a pitched roof, more work now, but over real long term likely less. Near flat roofs in a country that has a lot of rain and wind aren't ideal (as you're no doubt aware). 

Full marks for your industry, but make sure it's in the best direction. You don't want some insurer refusing to pay out in the future etc.. should there be some extreme event. 

We are at the absolute top of our budget already, we could not afford to actually change the shape. At that point we might need professionals in, definitely need a lot more materials (the roof is enormous) and need a lot more time than we have too. 

The pitch is 6 degrees, so not totally flat. If we get this right, it should be fine good for a long time to come. We just have to get it right for 130²m!! 😬

The upstands around the chimney and velux windows are going to be the hardest bits, and that's where the worst leaks were previously too. 

There’s an area of flat EPDM roof outside my upstairs bathroom. When I’m sitting on the loo there’s plenty of time to admire it. The current roof was done by somebody who knew what they were doing - it’s really neat and secure around the upstands and corners. The previous version was done by somebody who didn’t know what they were doing - it looked sloppy and it wasn’t long before it leaked. Based on that, I’d recommend that the person who does the tricky bits of your rubber roof should be whoever can do the neatest hospital corners on the bed. If only fitted sheets hadn’t eliminated that skill a few decades ago. 

Is there provision for ventilation somewhere in the buildup? Otherwise condensation (and then rot) in the OSB is going to be a risk.

Other thing I meant to warn you about was to avoid any product that sounds like it might be a character from a Harry Potter book. Oops, too late...😂

My cousin did an EPDM roof on his dormer window, but it was a single sheet rather than needing to weld the joins like ours, but he did still have to do some corners. He is project managing for us.

We also have my brother-in-law here and he has used something similar in the past (not on a roof). They are the two technical and precise people! I am humphing materials around! My cousin has done extensive renovations on his own house and has done them excellently.  They are planning to just take it slowly and work things out very carefully. 

Yes, we have thought about it. We concluded that we would ventilate in the house as it is simpler and we have no loft space. We already have extraction fans in the kitchen and bathroom, and we sleep with our window open every night, even in winter. The other rooms are used less anyway, but also have trickle vents on the windows, which should be enough we think. They old roof had no ventilation but only a few bits of rotten plaster board, and that was at points where there was definitely leaks. 

Good luck with an exciting project!

I think you've described an unventilated warm roof as proposed. You haven't mentioned a vapour control layer in the build up (warm side of the insulation.) The VCL is crucial in an unventilated warm roof. The manufacturer of the roofing membrane should offer technical support if my comments raise doubt.

So the insulation is onto ply boards, but under that we have a little of the traditional wool style insulation and then insulated plaster board as the ceiling layer of the house. Do we still need another VPL? And where in all that layering would it go?

The VCL would be laid over the ply deck. Adding insulation below the VCL is problematic because of the risk of the dew point (condensation occurring) moving inside the construction (bad.) A system manufacturer (membrane or insulation) could carry out a U-value calculation for you that included a condensation risk analysis (normally free) to justify/check the build up. Using a bonded board underlay is useful in some ways as they are essentially a vapour barrier but they aren't typically considered adequate as a VCL in relation to an unventilated flat roof.

Apologies for throwing out unhelpful fragments of info. Generally the diagrams for construction types are quite simple but life isn't(!) particularly with retrofit. I would suggest Googling the manufacturer of the membrane, give them a call to discuss and follow up by e-mail so you have a record of any recommendation. Tell them very precisely what your proposed construction is and listen to their advice. You will know what your constraints are; what materials are already purchased etc look for a path of least disruption that fits a good practice solution. One option may be to ventilate below the waterproofing / above the insulation (with no VCL) although that requires some complexity at eaves etc again, refer to the manufacturer.

Do you have a building warrant? Normally they require this sort of info, I think.

But we already have insulation underneath the ply deck. 

From the inside out we have: insulated plasterboard (X2 in some places), probably normal plasterboard (original ceiling), original wool insulation, original ply boards, then our additional kingspan and OSB. So if we put a VCL in on the ply board, it would have more insulation under it than over it. Should we be adding something to the house ceiling as a VCL?

In reality, we are too late to add anything into the mix now. We have to start getting the Resitrix on tomorrow, partly due to time restraints of our very kind family and friends, and partly due to weather windows in Argyll definitely not lasting long enough to get supplies delivered, fitted and then refitting what we have already done. Deliveries take forever to reach us and cost a fortune too!! So I think we have what we have and we will need to just make sure we have in house ventilation well sorted.

No. My understanding is that it's only needed if you are changing the structure of the roof, so what ExiledScot suggested up thread. I'm pretty sure it's not required if there is not structural change. 

Makes sense 

I would Google a bit about roof build ups. What you have may well be fine but getting it wrong could be expensive long term for the cost of a membrane.

We had a flat roof on our house growing up. It was a constant pain.

One of the many issues with ours was the felt wasn't properly tied in to the wall and water found it's way in.

One of many issues with it.

The biggest issue of the felt layer we removed off this roof was that lead flashing around the chimney was routed underneath the felt!! It was just acting as a funnel! 

The metal layer that was on top had been constructed to have ventilation along the ridge....but the felt layer under it didn't allow for any ventilation!! So it was just a ridge of metal sheeting with a gap under it which meant in southerly winds the rain was driven in to that space, and then it ran down the old felt layer and then back down the lead flashing tunnel at the chimney!!

We have to have a waterproof roof by Tuesday, that's when we lose our technical people who have the practical skills. We cannot add another layer now! 

There was no membrane previously and, as far as we can tell, moisture damage appears to have been from above rather than below 

That is hilarious. How does that happen? We effectively didn't have any flashing, which I think might be a slightly better situation than your funnel flashing. I think flat roofs may attract DIY bodgers.

At least it will be a million times better soon.

I think it happened because we are in mid Argyll, so you are lucky if any builder even turns up, so the cowboys can flourish. 

Yes, I am pretty certain that ours will be better! It certainly can't be worse!

I did some googling around about the VCL. It appears kingspan is considered a VCL. The thing I read said that insulated plasterboard also doesn't require a VCL. I guess adding it would have been belt and braces, but I think we are ok 🙂

I am back at work today, so out of the process now. It's a shame, as I would have been interested to see the Resitrix process. 

I think in reality, the various foiled insulation layers in your presumably intact ceiling will keep most of the vapour out. Perfect is nice but good enough is good enough and often all that's realistic. Either way it'll be miles better and drier than the rotten mess you've taken off for plenty of years yet.

Jk

Not sure if the roof drops into a gutter, but I've a low angle metal roof that goes into a gutter and I slid this plastic in under the metal to prevent back tracking of water underneath and divert into the gutter. Siliconed in.  Quite cheap.

https://www.eurocell.co.uk/fascia-and-soffits/ventilators-and-accessories/g...

It does drop into a gutter. We have some manufacturer supplied trims which I think are intended to do this, but I will bear this one in mind if they turn out not to be sufficient. 

Thanks 

Roof is largely finished. Still needs a few bits of trim and a few other wee things. 

This is one of the velux windows before the metal casing was reinstalled. This was what was looking like being the most technical, so this looks like they have really managed it well. 

Looks nice and tidy.   (Weird - from your photo there it almost looks like the sun is shining!)

Commiserations on having to go to work instead of getting involved yourself..

It's just good lighting. Don't be fooled 

We have had the most amazing weather for it. There has barely been a cloud in the sky every day! Although yesterday morning the start time had to be delayed due to ice on it!! We have struggled to keep up with the consumption of cold drinks, ice creams and suncream! We have absolutely lucked out.

Here's another picture from yesterday showing typical conditions 

I presume for the chimney you are removing pointing in a ring around it, then cement in metal trim/flashing(plate or lead), with plenty of over lap over the roof. The uphill side is curve so it channels around the sides. 

I believe that has happened. I wasn't home yesterday or today but I think that was this morning's job. 

It is apparently finished except for some trims as they didn't send the right fixings for them!! But they are just cosmetic I think. So essentially we have finished 😀

A beautiful, shiny new roof 😃 trims shouldn't take too long once the fixings come.