Type of roof for shed

The_B_Man

I'm getting a block shed built in my garden and the builder suggested a flat fibreglass roof (not sure if its 100% flat or has a slight incline for drainage). Someone I know suggested an insulated corrugated roof would be better.

The shed will be an office and will be powered and plumbed and could potentially become a granny flat in the future.

I'm wondering the best type of roof for keeping the heat in etc.

I've been trying to read up on them and they basically seem the same. Both last about 25 years, but I haven't been able to get prices.

Is there generally a better regarded roof than these, or would they be acceptable? Or should I tell the builder I don't want a flat roof and go with the standard wood beams and roof tiles like my house?

Thanks

Ddad

To the best of my knowledge if it is a planning exempt structure you are meant to match the materials of the main building, but I'm open to correction on that. It might cost a bit more but it should last and be more in keeping with your own house.

The_B_Man

The builder suggested flat fibreglass and I've seen one he's done on a neighbours house. It looks very modern and stylish the way its done.

But fashion changes so it might look useless in 5 years. TBH I'm not bothered by looks to much, more about longevity, insulation and being waterproof.

I've been googling the differences between fibreglass and insulated sheeting to get a definitive answer but there's none from what I can see. So I'm starting to think they're all basically the same.

The Continental Op

I redid an old flat roof in fiberglass last summer. Its not a cheap way of roofing but life expectancy is in the region of 30 years. You can go cheap on fiberglass or expensive. I'd go for the expensive option which involves thicker glass fiber mat and is much thicker and stronger.

I took an old flat roof stripped off the felt, laid down 50mm of insulation slabs (2x 25mm? might have been 100mm??) then 15mm plywood which was screwed down through the insulation to the joists then and put a fiberglass roof on top of that.

The_B_Man

Thanks for the info.

Would you be able to give a ball park figure of the cost last year? I think he was quoting me about 5k for it.

I'm trying to figure out if i can get 20+ years out of a cheaper roof material, without compromising on insulation. If I can save a couple of grand then i'll go for it.

The Continental Op

I can't say accurately because I overdid it and bought more materials than necessary. Knowing how to do it now I'd say there is a lot of money in the materials. I'd also want proof from the roofer of the materials used as there is money to be made doing a cheap job with minimum materials and charging for top quality - the consumer wouldn't spot the difference.

The labour part is skilled, I messed around a lot working it all out but once the roof is ready a good contractor should be in and out fairly quickly. Watch this guys videos - think there are 4 in the series to see what's involved.

https://www.youtube.com/watch?v=xT9YsGBU0Fk

Lumen

From what I've read there's no such thing as a detached granny flat, i.e. you won't ever get planning permission for someone to live in it, except temporarily during a house renovation.

Include decent overhangs in case you want to add external insulation later, and consider an insulated slab.