One for the roofists

[Rrobson]

A couple of quick questions about a new roof on the garage. It currently leaks like a sieve and is fibre cement (maybe asbestos but if it is I’ve got all the gear and been on countless courses so I’m familiar with how to deal with it) so it needs to go. Garage is a pre-fab one.

I’ve got hold of some second hand, (but in reasonable condition), insulated panels 80mm thick which are 8m so will span the whole length in one run but need trimming. Is there any paint recommendations for this material to seal the cut edge? I’m not sure the wife likes the colour either, so can I over paint in a different colour?

Next question, the current fall runs towards the back. Is there a reason why I couldn’t change this so the fall is towards the front? I understand rain will run off at the door end, but there is a drainage channel in front of the door and guttering should catch most of the water? I could really use the extra height at the back.

When installing the new panels, should I seal the overlaps or is it not worth bothering?

Finally, the current angle iron beams are spaced every metre-ish. That should be sufficient for supporting the new panels?

Thanks

 

[angellonewolf]

when you say 2nd hand ones that have holes already drilled in them ?

 

[Rrobson]

Unfortunately yes, but those that don’t align with the current spacings of the beams will be having a sealing washer with a nut and bolt arrangement. Far from ideal I know but if they last a couple of years I’ll be happy.
I’m hoping I can utilise most of the holes because I’ll be manufacturing new beams to lift the height slightly.

 

[angellonewolf]

i know new the sheats are expensive but i can see doing all the bother of a new roof that will only last a couple years pays the money and have it done for 20 years

 

[gaz1]

is this a rear garage or side garage or is it a front garage

a front garage you cant change and you have to follow the line of fall

if its a rear garage you can change it

if its a side garage you also cant change it and would need to follow the fall path as most garages fall too the rear than thats the way id go if you want no changes

all depends on how your garage is made of if brick you can put new joists where the holes are and screw as normal with the used sheets this is what i did and therefore didnt have to put new holes into the material i just painted the holes to make them last much longer as drill holes never get painted and this is where they can rot

angle iron beams i presume a prefab garage are they just flat pieces following the fall of the roof and also depending on where your garage is placed can you advise before i can answer

 

[Rrobson]

i know new the sheats are expensive but i can see doing all the bother of a new roof that will only last a couple years pays the money and have it done for 20 years

I appreciate the comment, and I completely agree, however they were incredibly cheap, and I don’t envisage living here in a couple of years time. Plus the gear in the garage is really suffering doe to water ingress.

@gaz1 yes, prefab. Beams are two angle sections with a couple of vertical supports so the top and bottom is flat (imagine a side profile like this >>> ] )
Garage is behind the house although it is at the boundary, I’ll put a satellite view beneath.

Yellow being the boundary, red obviously the garage

 

[bricol]

I roofed mine with seconds panels 100 ish thick - my supports are probably same spacing as yours - 6m-ish long, 5 supports, a beam at front and back. I sealed the overlap as I had some sealant.

I wanted more headroom than the prefab panels I used would give me - so I simply lifted the supports up on 50x50x6 angle bolted to the sides where the originals had been, up to the max roof line under permitted development - I also ran lengths of angle around the top of the "wall" of panels to align them, bolted through to give some strength. Infilled the gap with plywood, bolted where ti touched, clad on the outside with the single skin roof panels cut down to suit.

None of the untreated cuts have yet corroded in the ten years plus its been up.

 

[Rrobson]

@bricol sounds like you’ve done exactly what I was planning on doing, apart from running angle around the perimeter and cladding the outside. I was hoping to clad the exterior with the insulated panels inside edge out which is plain white but the wife wasn’t right keen on that unfortunately…

 

[gaz1]

its at the rear great solves the problem

jack up the roof note the 3x2s as they are sat on top of the angle iron and are fastened through the angle iron to the wood whilst the roof is fastened to the 3x2s



another forum member followed what i was saying

Another roofing question.

keep it simple and build the frame up barge board it and fit everything on it then fill with insulation built the same way just not with large gaps

www.mig-welding.co.uk

as its the rear of the property you can lift up the roof and insulate it as well as use the original holes as well as fasten new holes into the 3x2s at the main points

you can also change the slope if you want

 

[Rrobson]

Thanks for clarifying that, I hadn’t even considered those implications of changing the slope. I had thought about a pitched roof but that’s far too much work!

Just the question of paint?

 

[gaz1]

Thanks for clarifying that, I hadn’t even considered those implications of changing the slope. I had thought about a pitched roof but that’s far too much work!

Just the question of paint?

if you lift it up you can insulate it out like in the link because you also have the extra wooding in as well you can also use the original holes to fasten too id add more holes to the cross beams as well as thats the main structure hold down

the roof panels will fit over the side by 4" over the wall depending on the material that you use because your highering it you can change the slope to the other way if you want but the lift is more than enough to have a good 4" insulation and if your roof sheet has it whatever extra it has

 

[slim_boy_fat]

Yellow being the boundary, red obviously the garage

Does your neighbour's [on the left] encroach onto your side?

 

[Rrobson]

@slim_boy_fat not at all, but I agree that it does look like it on that aerial shot! We considered extending to the rear, and if our extension tied into theirs, ours would technically be over their boundary by a couple of inches. Otherwise there would be a two or three inch gap between them if we went right up to the boundary. The aerial photo isn’t right above, it’s at a slight angle and I haven’t drawn that yellow line very well… maybe I should have put “rough” boundary!

 

[Nomad]

I put up a sectional garage, all wall panels were the same height. A steel frame every metre / yard gave the slope for the roof.

It would have been easy for me to remove all the steels and fit them in reverse order so the slope is ran the oppositions direction.

Maybe an easy option for you?

 

[Rrobson]

@Nomad thanks for the suggestion, I had initially thought about doing that, but im desperate for some more height so im just going to make new. More work yes but I can do that before I start removing the old roof. It’ll gain me at least a foot at the rear which will be surprising useful. It would give me more options for milling machine if I decide to upgrade my current machine, but even that only has a few inches spare above it so there will be room for extra lighting and storage.

 

[gaz1]

becareful as those cross pieces hold your walls together hence why i havent messed with them

if you go up you need to create an angled piece to to keep the wall tied together with the angle iron

a knee brace roof truss will give you height as well as keep your walls together

 

[bricol]

@bricol sounds like you’ve done exactly what I was planning on doing, apart from running angle around the perimeter and cladding the outside. I was hoping to clad the exterior with the insulated panels inside edge out which is plain white but the wife wasn’t right keen on that unfortunately…

I only clad the plywood infill panels, so the plywood and the sheet overlaps the top of the panels - still pebble dash below them.

To save the hassle of making new cross pieces, I just bought some C-section purlins from a local suppier - bolted to the vertical angle bolted to the sides every other panel.

I stayed with a flat roof, with a tiny slope (2 degrees rings a bell - all one sheet length, so there's no leaks) to maximise internal room.

 

[Rrobson]

@gaz1 See photo below. It is not my garage but one from Facebook. My garage is 3m wide, the one in the photo is clearly wider, but the arrangement of the closest beam is the same as mine throughout. Two uprights either side, then two horizontal opposing angles along with a couple of vertical ties.

I was planning of putting some angled stays in to brace the cross pieces, similar to the ones further back in the photo. Is that what you mean?

@bricol i hadn’t considered reducing the fall, I was going to keep it as is but have it the other way. Suppose I could have a minimal slope to the front or the rear in that instance as long as water can run off? You’ve got me thinking now…

 

[gaz1]

I was planning of putting some angled stays in to brace the cross pieces, similar to the ones further back in the photo. Is that what you mean?

yes its called a knee brace as it allows you to lift the roof higher whilst holding in the sides of the walls

 

[bricol]

@gaz1 See photo below. It is not my garage but one from Facebook. My garage is 3m wide, the one in the photo is clearly wider, but the arrangement of the closest beam is the same as mine throughout. Two uprights either side, then two horizontal opposing angles along with a couple of vertical ties.

View attachment 420589

I was planning of putting some angled stays in to brace the cross pieces, similar to the ones further back in the photo. Is that what you mean?

@bricol i hadn’t considered reducing the fall, I was going to keep it as is but have it the other way. Suppose I could have a minimal slope to the front or the rear in that instance as long as water can run off? You’ve got me thinking now…

A similar picture to that was my inspiration, so in effect I recreated the roof supports, just with longer angle at the ends to lift it, but also extended down, so I could bolt through the upper of the two holes originally used, and through a new lower one.

I recalled from many years ago the advice for the slope for drainage in a pit to house an industrial wash plant - figured if it worked there, it would work just as well for roofing panels with no joins - so far it has. I have more hassle with water coming under the panels - thought I'd sorted it after the first flood earlier this year - but it did it again last week in less heavy rain than we've had many times since - must be down to the direction the storm is coming from.