I'm done with bodging... what are my options for re-roofing my garage?

[W.olly]

I have just redone my workshop with the composite sheets, dead easy and get in different colours. Mite look industrial but easy to fit as self supporting. Can be cheap is you get used or off cuts etc. this one cost me £300 for 5m x 4m coverage. and another load i got for the rest being £200 for 3.6m x 5m coverage.

 

[More Amps]

Shame you don't like EPDM, I put it on my shed roof (approx 12' x 8') total cost of rubber and glue came to about £200, and has a 30 year guarantee with an "expected" life of 50 years - more than long enough to see me out!

 

[John Hale]

I'm thinking of screwing wooden battens to the angle iron of mine then removing corrugated sheet roof replacing that with ply then covering the ply with torch on felt. To help cut condensation. Making it easier to insulate too.

Hopefully a future plan.

 

[gaz1]

I'm thinking of screwing wooden battens to the angle iron of mine then removing corrugated sheet roof replacing that with ply then covering the ply with torch on felt. To help cut condensation. Making it easier to insulate too.

Hopefully a future plan.

2" wood batterns across from your wood allows you to lay 50mm insulation inbetween the batterns

then fit the plyboard onto the batterns and whatever roof stuff you want to use

cheap insulated and water tight

just add another 2" below and you have your 4" insulation layer

 

[hooblah]

I've been giving this a bit more thought...

I've come to the conclusion that I may as well replace the roof, rather than covering it in some sort of paint. The quickest and cheapest method will most likely be steel/plastisol sheets. Cost of tile effect sheets is around £30 for a 3m length, so about £150 for 15m, plus delivery and fixings etc.

Now what are the nuances about fitting these sheets, or things to be aware of?

There are a few things I'm not sure about:
1. The sheets are available with a plastisol or polyester coating. What's the difference?
2. They come in 0.5mm and 0.7mm thick. Is there a distinct benefit in going with 0.7mm?
3. The construction of the garage is that the back and front ends have a timber wall plate, with a central timber beam that runs horizontally. The roof sheets are fixed to these 3 points. Is this sufficient for steel sheets? At what point do I need to install z purlins?
4. Being a single pitch roof, the back end is higher than the front. The wall plate won't be at the same angle as the roof sheet, although the central horizontal beam is. Logically thinking, screwing through it into the wood will deform the sheet. How best can I get around this?
5. What do I do about the sides? As it is a cold roof, the high and low sides will be left open to allow for ventilation. What about the left and right sides? The left side of the roof butts up against a parapet wall.
6. What do I do if I find that the final sheet has too much overhang? Or is too short? If I cut the sheet it won't be protected by the plastic coating.
7. How long do the screws/fixings last before they perish and start letting water through?
8. It appears that insulated sheets are available for double the price, bearing in mind I already have a layer of insulation under the roof, is it worth going for that?

 

[Onoff]

The Cromapol probably didn't take properly as the sheets were dirty with loose, organic matter and degraded asbestos surface. Brushing off the crap beforehand probably wasn't enough.

It's expensive too Cromapol etc. I've probably done several hundred £s on various acrylic compounds on my dormer roofs which really need redoing properly. The best it took was when I cleaned the roof properly first. Saying that I still get water ingress on one particular corner and around one window.

I was thinking for your garage a broom clean with say No Nonsense Degreaser and jet wash on a scorching day. Yep you might get a bit of water ingress but hey ho. Once clean (could still be damp but I'd let it dry out a bit) then a paint with an acrylic compound. Maybe one of the black bitumen compounds as they are comparatively cheaper than the acrylic based ones.

Not sure though if jet washing an asbestos roof is a good idea? OK the water would keep the fibres down initially but would it just distribute them over a wider area to contaminate the environment over a wider area?

In an ideal world I'd redo my roof completely and use one of the liquid compounds like Desmopol. You use fibre glass edge trims, joint reinforcing tapes but paint / roller the stuff on. I like that it can be topped up/repaired any time and easily. Mate has just used a roller on system where you first put down a fibre mat then the two pack paint system. Like fibreglass but with less temperature / time constraints. That too can be recoated/touched up anytime.

I know who to call when I get rid of my garage roof, only 5 minutes from Meopham here. (Pronounced "Mepum" not "Meofam" btw! That's down the road from Wrotham...pronounced "root 'em"...).

 

[SierraV6]

I've been giving this a bit more thought...

I've come to the conclusion that I may as well replace the roof, rather than covering it in some sort of paint. The quickest and cheapest method will most likely be steel/plastisol sheets. Cost of tile effect sheets is around £30 for a 3m length, so about £150 for 15m, plus delivery and fixings etc.

Now what are the nuances about fitting these sheets, or things to be aware of?

There are a few things I'm not sure about:
1. The sheets are available with a plastisol or polyester coating. What's the difference?
2. They come in 0.5mm and 0.7mm thick. Is there a distinct benefit in going with 0.7mm?
3. The construction of the garage is that the back and front ends have a timber wall plate, with a central timber beam that runs horizontally. The roof sheets are fixed to these 3 points. Is this sufficient for steel sheets? At what point do I need to install z purlins?
4. Being a single pitch roof, the back end is higher than the front. The wall plate won't be at the same angle as the roof sheet, although the central horizontal beam is. Logically thinking, screwing through it into the wood will deform the sheet. How best can I get around this?
5. What do I do about the sides? As it is a cold roof, the high and low sides will be left open to allow for ventilation. What about the left and right sides? The left side of the roof butts up against a parapet wall.
6. What do I do if I find that the final sheet has too much overhang? Or is too short? If I cut the sheet it won't be protected by the plastic coating.
7. How long do the screws/fixings last before they perish and start letting water through?
8. It appears that insulated sheets are available for double the price, bearing in mind I already have a layer of insulation under the roof, is it worth going for that?

Ok here goes….

1. Plastisol is thicker and more durable, polyester is basically a thin coating of paint. It’s perfectly fine but is more prone to getting scratched etc.

2. Over a short length and unless you’re going to walk on it probably not.

3. you definitely don’t need Z purlins! The front and rear need to be fixed properly and I’d want a single row of intermediate fixings if possible.

4. Ideally you would add an angled length of timber to the wall plate but as long as you don’t over tighten the fixings it will be fine.

5. The side abutting the wall will require a flashing. The other side should be fastened tight against the wall plate.

6. The sheets are cut anyway and will have bare edges.

7. Longer than the sheets!

8. Not really IMO.

Hope that helps!

 

[gaz1]

I've been giving this a bit more thought...

I've come to the conclusion that I may as well replace the roof, rather than covering it in some sort of paint. The quickest and cheapest method will most likely be steel/plastisol sheets. Cost of tile effect sheets is around £30 for a 3m length, so about £150 for 15m, plus delivery and fixings etc.

Now what are the nuances about fitting these sheets, or things to be aware of?

There are a few things I'm not sure about:
1. The sheets are available with a plastisol or polyester coating. What's the difference?
2. They come in 0.5mm and 0.7mm thick. Is there a distinct benefit in going with 0.7mm?
3. The construction of the garage is that the back and front ends have a timber wall plate, with a central timber beam that runs horizontally. The roof sheets are fixed to these 3 points. Is this sufficient for steel sheets? At what point do I need to install z purlins?
4. Being a single pitch roof, the back end is higher than the front. The wall plate won't be at the same angle as the roof sheet, although the central horizontal beam is. Logically thinking, screwing through it into the wood will deform the sheet. How best can I get around this?
5. What do I do about the sides? As it is a cold roof, the high and low sides will be left open to allow for ventilation. What about the left and right sides? The left side of the roof butts up against a parapet wall.
6. What do I do if I find that the final sheet has too much overhang? Or is too short? If I cut the sheet it won't be protected by the plastic coating.
7. How long do the screws/fixings last before they perish and start letting water through?
8. It appears that insulated sheets are available for double the price, bearing in mind I already have a layer of insulation under the roof, is it worth going for that?

if you use another material other than metal you will have to frame it out so be warned you might get away with the 3 supports but id advise fitting a board



because you have the metal garage frame underneath all you would need to do is run 3x2s across the apex thats all ive done and insulated between them

this was explained via this post but he wanted 4" insulation installed so he needed a full frame to be built to spread the load

Another roofing question.

If that was mine I'd be inclined to do away with the steel completely. Internal 2x4 studwork all the way around. Insulated and boarded and will support the josts. Joists across the short run and firrings for a fall

www.mig-welding.co.uk

ask @123hotchef as he had the same thing highered his roof and fitted the rear wall trim

How best to re-roof this

the roof sheet valley looks like this the red being th top of the roof sheet and lowest point of it the grey is the lead or tin sheet underneath to create the wrap around seal you need for the corner the valley sits on top of the roof box profile high point at one end drawn in black you will...

www.mig-welding.co.uk

 

[GRW]

A mate does fibreglass flat roofing as a big part of his construction works as an independent builder. I had him do my Workshop roof about 10-years-ago.
Its great and no reason done properly that it won't last decades.
basically the roof (assuming solid supports) gets clad with Sterling Board and then Glassed. Reveals and Gutters, Soffits etc can all be added as required to direct rainwater.

Not as cheap as slapping on some Bitumen roofing felt or similar, but there's absolutely no comparison to a well done Glassfibre Roof IMO.

 

[hooblah]

The Cromapol probably didn't take properly as the sheets were dirty with loose, organic matter and degraded asbestos surface. Brushing off the crap beforehand probably wasn't enough.

Not sure though if jet washing an asbestos roof is a good idea? OK the water would keep the fibres down initially but would it just distribute them over a wider area to contaminate the environment over a wider area?

I got on top of the roof and jet washed the life out of it a couple of summers ago. You could eat your dinner off it after I was done. I then applied cromapol with a block brush.
The jet washing may have loosened fibres. It's no real concern since the air we breathe is full of asbestos fibres anyway. Besides, this is asbestos/cement mix. It's hardly dangerous.

Ok here goes….

1. Plastisol is thicker and more durable, polyester is basically a thin coating of paint. It’s perfectly fine but is more prone to getting scratched etc.

2. Over a short length and unless you’re going to walk on it probably not.

3. you definitely don’t need Z purlins! The front and rear need to be fixed properly and I’d want a single row of intermediate fixings if possible.

4. Ideally you would add an angled length of timber to the wall plate but as long as you don’t over tighten the fixings it will be fine.

5. The side abutting the wall will require a flashing. The other side should be fastened tight against the wall plate.

6. The sheets are cut anyway and will have bare edges.

7. Longer than the sheets!

8. Not really IMO.

Hope that helps!

Excellent. I don't plan on walking on it unless it's to make repairs, so probably never.

if you use another material other than metal you will have to frame it out so be warned you might get away with the 3 supports but id advise fitting a board

The current roof isn't 'framed out'. I imagine asbestos/cement sheets are heavier than steel sheets. I can't see it causing a problem if I replace like-for-like, unless you know otherwise?

A mate does fibreglass flat roofing as a big part of his construction works as an independent builder. I had him do my Workshop roof about 10-years-ago.
Its great and no reason done properly that it won't last decades.
basically the roof (assuming solid supports) gets clad with Sterling Board and then Glassed. Reveals and Gutters, Soffits etc can all be added as required to direct rainwater.

Not as cheap as slapping on some Bitumen roofing felt or similar, but there's absolutely no comparison to a well done Glassfibre Roof IMO.

Seems like a lot more cost and effort than going with steel sheets.

 

[fizzy]

I would just use an epoxy paint. It should last 10 years at least if done right and much easier.

https://www.jotun.com/Datasheets/Download?url=%2FAG%2FAG__16560__Jotamastic+90__Euk__GB.pdf

Used on oil rigs and cargo vessels etc.
Can be brush applied.
It will seal the asbestos totally.

 

[GRW]

(Glassfibre Roof) Seems like a lot more cost and effort than going with steel sheets.

For sure. There's nothing wrong with Profile Sheet Roofs (Wriggly Tin ) at all. All I was suggesting was that a GF roof was durable and effective. It also looks better and might be said to offer a more insulating (in terms of heat and noise transmission, condensation etc) roof than a Wriggly Tin job.
You could of course go for the Insulated Profile Sheets (or add Kingspan or similar) - but then you are seriously eroding the cost benefits of a Tin Roof.

 

[hooblah]

I would just use an epoxy paint. It should last 10 years at least if done right and much easier.

https://www.jotun.com/Datasheets/Download?url=%2FAG%2FAG__16560__Jotamastic+90__Euk__GB.pdf

Used on oil rigs and cargo vessels etc.
Can be brush applied.
It will seal the asbestos totally.

It's still a bodge. Please re-read my posts as to the condition of the roof/paint.

For sure. There's nothing wrong with Profile Sheet Roofs (Wriggly Tin ) at all. All I was suggesting was that a GF roof was durable and effective. It also looks better and might be said to offer a more insulating (in terms of heat and noise transmission, condensation etc) roof than a Wriggly Tin job.
You could of course go for the Insulated Profile Sheets (or add Kingspan or similar) - but then you are seriously eroding the cost benefits of a Tin Roof.

I already have multifoil insulation. There's little benefit to be gained, especially if the garage gets ripped down in the next 10 years. I've decided i'd rather put up with the looks of steel sheets than invest more time and money into something that I don't want to invest in.

 

[SierraV6]

I already have multifoil insulation. There's little benefit to be gained, especially if the garage gets ripped down in the next 10 years. I've decided i'd rather put up with the looks of steel sheets than invest more time and money into something that I don't want to invest in.

If you go with Slate Blue even ordinary box profile looks quite nice IMO.

 

[DennisCA]

I'm building a shed and putting a sheet metal roof on it, will be uninsulated so condensation might become an issue. If I got my english terms right, I will put a condensation membrane between the rafter and the purlin. That will create a small area between the sheet metal roof and the sheet. Condensation can drip down on this sheet and them runs freely out the sides of the roof and into the gutter. Very simple to add when you build the roof new. Air will also be able to circulate freely inside here and the roof will be vented at the top. This design works for a roof with a big enough slope, not sure if it's applicable to your roof.

Flatter roofs IMO seem to have more issues than sloped ones.

 

[gaz1]

I'm building a shed and putting a sheet metal roof on it, will be uninsulated so condensation might become an issue. If I got my english terms right, I will put a condensation membrane between the rafter and the purlin. That will create a small area between the sheet metal roof and the sheet. Condensation can drip down on this sheet and them runs freely out the sides of the roof and into the gutter. Very simple to add when you build the roof new. Air will also be able to circulate freely inside here and the roof will be vented at the top. This design works for a roof with a big enough slope, not sure if it's applicable to your roof.

Flatter roofs IMO seem to have more issues than sloped ones.

just so you know its better to jack the roof sheeys higher otherwise the material rots from underneath

Insulating a shed/garden room etc.

Quick question about where the breathable membrane would be fitted... In this diagram, the orange is the external cladding with vertical battens every 54cm or so. I'm going to fix spacer fixings to the battens that the PIR will rest up against (and the OSB in front of the PIR, which isn't shown...

www.mig-welding.co.uk

 

[DennisCA]

I am not quite sure i follow. I assume you mean condensation would gather on top of the membrane and pool against the purlins? I guess that's an issue but my idea was leaving the membrane a little slack, which would result in condensation running to the center of the membrane and under the purlin so it doesn't collect against it as easily. Water should flow freely when condensing and air flow will help dry the wood again before rot sets in. We also only have conditions like that a short time every year.

 

[gaz1]

unless the steel sheet is lifted it can and does suffer from rotting of the metal as the metal roof sits onto the felt therefore does not run off

 

[DennisCA]

OK, this is how I was planning to do it (this is from a barn). Membrane is one "layer" higher than in your picture, not the way to do it for a house people live in, but for a barn or shed I think it's ok. You still get air flow.