Need to repair wooden facias of pre-fab concrete garage.

[CmdrBond]

The ends of my garage were damage a little while back in storms, and while everything inside is still dry, the roof at one end is beginning to sag (see pictures below).
Will it be possible to replace the ends without removing the roof, or at the very least only part of the roof?

I plan on using marine-ply and treated timbers, but also to use horizontal upvc facias instead of the vertical wood currently used.

The rear of the garage will be trickier as it backs on to a neighbours shed, although if removing the end roof panels, this will not be such an issue.

If I can repair with the roof in situ, Would a T made out of timber and jammed in place be enough to take the weight of the roof while I replace the end - or would I need to rent supports?

Pictures - click to enlarge

 

[tim00]

Fair play to you or whoever had a go at the original build - you got it up and it served it's purpose. Now, however, it will be far more difficult to effect remedial work on all above the garage door.
You could rig a 2x4 frame up to prop the roof while you carry out repairs, but that roof looks shaky. My concern is, if you remove that 2x "lintel" over the door then the walls and roof might spread and fail.
You would have to build a "proper" truss and fit it piecemeal into position, much time and effort for a dubious reward.
Something will have to be done as the sag will get worse and possibly dangerous.

 

[CmdrBond]

Cheers for the reply.

The garage was erected over 20 if not 25 years ago by the previous owners or on behalf of the previous owner by the company that supplied it.

To be honest, the thing seems pretty stable. I will chuck a spirit level up against the walls, but they don't look out of true. One side of the garage is next to the garden wall too, so that may help.

There are 3 or 4 of the metal cross braces/roof supports you can see in picture #5.

If I do make a go of it, can I get away with sorting out a 2x2 frame and put the ply up afterwards?

 

[tim00]

2x2 is too light. Pin two no 2x6's and use them on edge as your lintel and bottom truss chord. Then use 2x4's to pre-fab your truss - angled braces etc. Demolition and installation will be a two people, two pair of steps job.
Have everything ready to go including a SDS or hammer drill, first thing in the morning. Dont do a bit and then leave it for later.

 

[CmdrBond]

Cheers for that - I have gone and done a bit of measuring.

The total length that the lintel/bottom chord needs to be is 9'6", I will need the inside one to be 9" shorter otherwise there will be a 2" unsupported overhang to the front.

I will need to shape the ends as the far edges only give me a 5" space, 6" comes at the 9" point in from the edge. So the ends of the roof will be directly supported on the lintel/bottom chord.

I have sat down and tried to work out the necessary angles to cut into the 2x4 to get the pitch right. Whatever I do - the maximum height between the top of the 2x6 and the bottom of the 2x4 will be 10" - I don't think I will have enough space for angled braces, just a vertical one in the centre.

If I am making a complete pre-fabbed truss with a bottom chord of 2x4 to put on top of the lintel, then that vertical space will only be 8".

Not sure why I need the SDS/Hammer drill as all fixing points are already there - If any thing needs drilling it will only be rusted bolts as far as I can see.

Once I have the frame sorted - should put a ply facia on before the UPVC, or just go strait for the UPVC. - Should I even bother with UPVC - should I just use shiplap timber to face it?

This might sound stupid - but is there any reason why I can't use 2x4 on it side, rather than edge, stacked on top of itself - ply-like?

 

[tim00]

The 2x6's alone, on edge, are the bottom chord/lintel, no 2x4 plate necessary.
Remove the duff ply and use the in-situ framing as a template to copy to suit, for angles and lengths.

Ply sheathing will stffen the truss but it's not necessary.
PVC seems to be the way to go. Stay away from wood.
You dont seem to have a ridge so i'm not quite sure how you would prop the roof? The corrugated sheeting will be fragile.

You might need the drill(s) for any fixing in concrete panels. Be prepared.

 

[CmdrBond]

...

You dont seem to have a ridge so i'm not quite sure how you would prop the roof? The corrugated sheeting will be fragile.

...

There are 4 metal bars that run the length of the garage, I have measured the height of these elsewhere in the garage (where they are at the correct height) and plan to wedge a bit of 2x4 under each one to prop the roof - does that sound good enough?

...

You might need the drill(s) for any fixing in concrete panels. Be prepared.

Fair enough - but I plan to drill out or hacksaw off any bolts that won't come easily and re-use all fixing holes. To be fair - the fixings I am removing should only be in the wood - I plan on leaving the ones in the concrete sides/roof alone unless absolutely necessary.

 

[tim00]

Yes, but only prop the central two "purlins", merely support them, dont wedge them up.

 

[CmdrBond]

Ok I won't "wedge", but I was planning to prop all 4, because of the sag I need to get all the fixing points in the right place - as the ends of the "purlins" connect to the truss.

 

[CmdrBond]

OK - I have been back in the garage and spent nearly 2 hours with a tape measure, bits of paper and a calculator.

Whilst I agree 2 bits of 2x6 and the rest of 2x4 will be the best, it is not going to be practical for me to use these size timbers. Also, on closer inspection, the current 2x1 timbers appear to be in reasonable shape, all things considered. The problem is that there is no support frame under the 2 central purlins, and as such the ply facing was providing all the support and has given way.

With all that in mind, I plan on doing the following.

Bottom Chord/Lintel - 1x 9'6" length of 2"x4" - I could bolt a second piece to it, but I don't see what this would achieve as there is nothing for the ends of it to rest on, so it (in my mind) doesn't add any support, and drilling holes into it to run bolts through would (in my mind) weaken the main lintel.

Top Chords - 2x 5' lengths of 2"x2" - cut to meet at the apex.

Apex Brace - 1x 11" lenght of 2x4" cut to fit to support the apex

Purlin Braces 2x 9 7/16" lengths of 2"x4" cut to fit at 10" centres from the apex to support the 2 purlins.

This is what it looks like in Google SketchUp (click to enlarge)



I will be using treated timbers and facing with marine ply before putting the fascia on. Do I need to add ply/metal gussets to the inside side?[/url]

 

[CmdrBond]

Well - spent the day at it - only done one end so far, and there are still some minor finishing touches to do. Its not perfect by any stretch of the imaginations, but it is a lot better than what it replaces.


45x90mm bottom chord/lintel
45x45mm top chord
offcuts of each for the supports
6mm ply facing
roofing felt

Here are the "after" pictures (click to enlarge)