How to replace garage roof rotted rafters?

[mody_moozy]

Hello, a few rafters of our garage roof have been heavily damaged by rain. The reason I believe is that the old gutter that was attached directly to the rafters, rusted and sagged, allowing rain into the timber behind. The long bottom piece of wood in this section that the rafters sit on (not sure what to call it) is also in really bad condition.

I'm hoping to either put a proper fascia board up or flashing and attach a new gutter. The garage roof is about 9m long and the other rafters seem good, just these 2, maybe 3 rafters are rotting. I'm wondering if it's possible to attach a fascia onto it to hang a gutter? See pics below.

 

[Dave-1]

Good Afternoon @mody_moozy 

I can suggest a way you can replace the rafters and that baseboard ontop of the brickwork. Tho I think there should be some sort of waterproof/rubber sealing between the timber and bricks. (outside my knowledge area tho suspect there is something.) Also the roof needs to be tied mechanically to the wall somehow.

I would use some ag props to lift and support the frafters either side of the rafter you are replacing, even using a scrap piece of timber to span the two rafters on one side for one prop and two rafters the other side for the one prop. Then slowly lift dial up the ag prop (it will be harder then you expect)

Once the weight is taken off the rafter to be replace, knock it out. You will needto remove the screws nails from the top side. This could be a problem depending on the strength of the existing rafters. If there is an issue I would once the weight has been lifted, saw the timber rafter into smaller sections so you can then saw it to the point of destrucyion at the nails/screws.

Once the rafters are replaced, then that board the roof rests on needs to be done. I would span three of the rafters with a piece of timber (decent size) and lift, keeping in mind you are going to still be turning the thread of the ag prop so it cant be right against the wall. Please note that you have power going from the wall to teh rafter you need to be cautious of.

Once ou have replaced the top board plus flashing! (think you need some kind of lead flashing under the board) Then you need to attach a facia to the outside of the rafters/joing plate. Paint it, then the guttering so you dont end up in the same situation. The guttering needs to have a small slope to it as to drain.

Dave

[EricL]

Hello @mody_moozy 

It's great that you've received excellent advice from @Dave-1. My only added suggestion would be to use a sabre saw to cut the old rafter and to secure it with rope so that it does not fall accidentally to the ground. Another tool I would like to recommend is a multitool with a steel cutting plunge blade. You can use this to cut the roofing screws or nails that are attached to the rafter. This is on the condition that the screws or nails are stuck and can't be removed.

Please remember to wear personal protection such as gloves, goggles and a mask when working on your project.

If you need further assistance, please let us know.

Eric

[mody_moozy]

Thanks @Dave-1 and @EricL for your suggestions! Is there any other smaller scale repair that can be done for the rafters or do you think it needs complete replacement. Here's an inside pic of the rafters in question:

[EricL]

Hello @mody_moozy 

Thank you for the extra photos of the rafters. If part of the rafter is still in good condition and only part of it has deteriorated it might be possible to do a cut-and -joint repair. However, I suggest engaging the services of an experienced builder and asking them to do a professional assessment of the rafters. Can they be joint repaired or do they need full replacement. 

Let me tag @Nailbag for his recommendations.

Eric

[Dave-1]

Good Evening @mody_moozy 

You could in theory do so, Cut the rotting section out, and then overlap the missing section with a new section and using several bolts join the two side by side together. 

The plate they are sitting on tho really needs to be replaced, so I would factor that into whichever way you go forward.

Dave

[Nailbag]

Hi @mody_moozy 

Though not an expensive repair if you can do yourself, it is a complicated one. It involved supporting the battens (These are the smaller timbers the roof is fixed to) with side of the main rotted cross members with Acro props. I would use 4 with 2 on either side of the rotted beam. I would hire them as they tend to have a cheap day rate.

Apply some slight lifting pressure on the props to take the weight of the rotted cross beams. Then remove the roofing screws on that beam above and work your way to remove the rotted beam itself so it can be replaced. If any electrical cables need to be disconnected and reconnected, you will need a sparkie to do those steps.

A decent handyman can also do this work for you other than the electrics as you may struggle to find a builder to relatively small job (to them).

Nailbag

[Nailbag]

Hi @mody_moozy 

Apologies, I didn't scroll up to see your original posted photos. The bottom plate the rafter beams are resting on being rotted complicate the repair as they need to be replaced to. Plus roof batten on the last row is showing signs it's on the way out too. Its possible that you use taller rafter beams in lieu of the bottom plate resting on the brickwork.

Unless your super handy and have a helper on hand, I would investigate having the repair work done professionally.

Nailbag

[mody_moozy]

Hi @Dave-1 @EricL and @Nailbag, thanks for your replies. Based on the advice given, I think I'll be reaching out to someone much more capable to assess and repair this roof. I appreciate your help anyway.