Reroof – Best Breathable Membrane?

paperclap

Hi all,

It's looking increasingly likely that I will be reroofing our house next year.

Roofing quotes are through the roof (ha!). I'm no roofer, but I feel I could pull it off. It's only a small 2-bed semi-detached bungalow.

Considering there is a huge shortage of tiles right now, I'm trying to plan ahead as much as I can.

We're backed onto a field, and just minutes away from the sea... so quite an exposed property, I suppose.

We've never suffered any condensation (that we know of) in the loft space. That said, we may not have had any condensation issues, because all our old bitumen felt is completely shot... so ventilation all through the gapes between tiles!

What are everyone's thoughts on the best breathable membranes?

DuPont, Klober, Cromar... many to choose from. Seems many roofers have a preference for one reason or another.

Thanks!

tacpot12

I tried some slate roofing on an outhouse recently. Putting the slates on was pretty easy, but installing the timber was a nightmare. I would recommend paying an experienced joiner if you need any woodwork to be replaced. 

As to a breather membrane, I would say that any branded stuff will be fine, you can shop around for what will be the cheapest for the quantity you need. (I used DuPont Tyvek on the outhouse, but it was such a small area cost wasn't a concern). Make sure you understand how it is supposed to be installed and price in the cost of any tapes needed to join runs of the membrane together. 

Make sure you know the weight of your existing tiles and select new tiles that will weigh no more than it. 

I think you are likely to have to improve the insulation in the roof in order to get building control sign off for the new covering. 

paperclap

Thanks tacpot12!

We're not going to be replacing any of our timber... unless we've got rotten timber, of course! Fingers crossed, we don't. If we do, I have someone in mind (yet to contact them, though) who I'm hoping can be on call for any issues with timber I run into.

Thanks for noting about the tape. I've seen a lot of roofers that don't use tape on horizontal joins. Do you need to? Would make sense – if there is any abnormally crazy weather, that joined join would circumvent water ingress (if it did indeed get past the tiles).

We currently have Redland 49 tiles. Not sure if we'll get Redland 49s again, or something entirely different. But yes, weight is definitely a major consideration.

Regs now require your ceiling insulation to be a minimum of 270mm, correct? Don't believe there are any regs for insulation in / around rafters. That would be odd.

warwick2001

When we got our roof....errr....re-roofed, our roofer used this stuff:

Roofshield Air and Vapour Permeable Breather Membrane - 50m x 1m Roll | Insulation Superstore®

According to him, its the best stuff he's used.

tacpot12

laurencewhymark said:

...

Thanks for noting about the tape. I've seen a lot of roofers that don't use tape on horizontal joins. Do you need to? Would make sense – if there is any abnormally crazy weather, that joined join would circumvent water ingress (if it did indeed get past the tiles).

...
Regs now require your ceiling insulation to be a minimum of 270mm, correct? Don't believe there are any regs for insulation in / around rafters. That would be odd.

Tape is necessary, especially in a coastal region. Generally, my advice would be not to follow what the professionals do. Most professionals are just following what they learned when they were apprentices 10, 20 or 30 years ago; times change and our knowledge of how buildings and building products perform have moved on. I would always recommend following the manufacturers' instructions on how to install their products. If a product seems to have a complicated installation process, you can always look for one that is simpler.

The Building Regulations don't mandate any minimum thickness of insulation, because the regs doesn't know how good the insulation you are fitting is, or where you are fitting it. Rather they require you meet a U-value of 0.16 W/(m2K). How you do this will depend on the type and thickness of the insulation, and where you fit it - it makes a difference if you put it between the rafters or over the rafters. You probably need to engage a professional who can do the calculation of the U value for you using information about the insulation you want to fit. A total thickness of 270mm of a branded glass fibre insulation is probably going to be enough,  but 'probably' won't satisfy the buidling regulations.