Garage Roof Replacement

[BIGbadmarky]

I'm very lucky to have two garages, side by side but they both have cement asbestos roof panels which are pretty old and cracked. As a result they let in a lot of water, rendering the garages fairly useless for anything other than storing rubbish i.e the wife's soft furnishings (seriously, I recently removed a skip full of cushions!!).
Quick question: is it roofs or rooves? I digress....

Anyway, I decided to replace the roof with a timber frame and an EPDM one piece rubber cover. I've checked with planning and as long as the roof remains under 2.5m it'll be fine. Building control aren't worried as the garages are detached from the property.

After a few design iterations and a rough attempt at costing the job I cracked on with the work.

Day one:
First job was to cut a door way between the two garages. FYI: the planning permission was for an extended garage not two separate garages so the permission would still be valid. I screwed some timber battens to the wall to give me a nice straight edge and drilled a load of holes in the mortar joints. I hired a 9" angle grinder for the job. I had read that they kick up LOADS of dust but I really underestimated just how much they generate.

I scoured out the mortar joints every few courses before cutting through the wall so it didn't all fall through in one big old block.

After a few passes with the grinder and a few taps with the persuader the wall fell through nicely.

Job done.
Second job was to pour a concrete footing for the timber wall at the end. I was planning on replacing the end wall with a timber frame wall.


Day two:
I started the second day by cutting the bolts securing the roof panels to the joists. I used some chunky bolt cutters for the job and they pinged off quite happily. I slid the panels down the roof following the fall and being careful not to scrape them too much. Fortunately it was a drizzly day so the panels were wet, reducing the amount of dust generated. In addition I wore an appropriate dust mask, goggles and old clothing that I could get rid of. With a lot of man power and brute strength the panels all came off without breaking them up. Word of warning: this is not a one man job. It dam near killed me.

Removing the panels revealed some very rotten joists which were basically held together with cobwebs. In addition, the brick work was very dodgy and big sections were quite wobbly.

 

[BIGbadmarky]

Day Three:
Removing the joists was fairly straightforward. They were quite rotten and not really secured to the walls so they dropped out without much fuss.

After the joists were out I spent the rest of the day patching up the walls and learning how to lay bricks. Its not as easy as lego but once I got the knack of a mortar mix (not easy in +25°C), I motored along quite well.
I installed a metal lintel over the door way I cut. It was not to support the bricks above the wall but to tie in the two parts of the wall and add a bit of stability.
By the end of the day I had bedded in the wall plate on the wall to the left of the image above (not on the pic). I had though I would be able to use a 1" x 4" timber for the wall plate but in hind sight it wasn't thick enough and didn't have the strength to to offer a flat surface so didn't really help too much! I picked a 1" timber as I was worried about the overall height of the roof.
Day four:
Things started to motor on the fourth day. I finished the brick work and bedded the second wall plate. I cut and fit the surrounding frame of the overall roof structure and temporarily fixed it with L shaped brackets. The end wall went up fairly quickly (thanks to a buddy with some experience). The long sides were jointed to avoid a butt joint. After the frame was in I fit the joists and by the end of the day the roof and end wall were looking fairly robust.


The roof was built with 2" x 6" C24 timber as was the end wall. The skin of the end wall was clad in 11mm OSB3 with a vapour barrier between the frame and the OSB. The frame was fixed with concrete bolts to the new footing I had previously poured and fixed to the side with hammer fixings.


Day five:
Being a Sunday I couldn't start too early with the power tools so I cracked out the sealant gun and and pointed the wall a little. The roof frame was strengthened with noggins (at a more civilised hour) and these were fit pretty quickly. After a bacon sandwich break the roof deck (18mm OSB) was fit with a 36mm overlap at each side (it'll make sense later).
Once the timber deck was on and secured the rubber roof was glued in place. The rubber is glued down with two separate adhesives: A WBA adhesive for the bulk of the roof and contact adhesive for the edges. The ambient temperatures were +25°C so I decided to leave the contact adhesive until later in the day, when things had cooled down a little. The WBA glue went off pretty quickly so I was pretty comfortable with the bond.
Once the roof structure was on and the rubber was down, I attached the roof to the walls with 1800mm twisted straps.


The bulk of the heavy work has been done and leaving only the lighter weight jobs to be done. Outstanding work includes sealing the roof and finishing the pointing, cladding the end wall and putting on the fascia strips around the roof. All things being well I should have the snagging done this weekend.

 

[BIGbadmarky]

This weekend I managed to do a few more jobs on the garage. I have drilled 10mm vent holes in the outer roof timbers (sounds daft but there is a reason) and covered with fly screen mesh. I read on this forum recently about a chap who had issues with mould forming on the underside of his OSB roof so I'm hoping the holes will allow the roof to breathe and reduce / stop mould from forming. The vent holes are in the top 50mm of the roof timbers leaving 100mm below for some rigid insulation once I'm happy no mould is forming (and I can afford it). Externally the vent holes will be hidden by the fascia boards (once they're fitted). I've not got any pics of this but I can post some if anyone really wants to see my handy work.

The other job this weekend was to shiplap the timber end wall. As per my previous post, I have replaced the up and over door with a timber frame wall. This is a 2" x 6" frame and has been boarded with 11mm OSB. I installed 19mm counter battens to the OSB and attached the 15mm shiplap to the outside. From what I read the counter battens need to be greater in depth then the cladding to allow ventilation behind and stop mould. The bottom board is a bit close to the floor on the right-hand side and will probably rot in a few year due to rain splash. Unfortunately I couldn't see a solution to this as the fall from right to left wouldn't allow the board to be placed any higher without exposing the OSB. I should've built the footing higher but hindsight is a wonderful thing!



I may yet retro fit some steel wire mesh on the inside of the wall for security but I'm not sure yet. It might be over engineering the solution to a problem which doesn't exist.

The top shiplap board was (roughly) cut around the fascia spacers at the top. I lost a chunk of my thumb in this process but it'll grow back! The rough edge will be covered once the fascia board goes on so should look neater. The shiplap went up fairly easily really. I cut all the board lengths to fit by hand as the walls aren't quite square. There's still some sealing to do and the boards will need to be finished but it looks reasonably robust for now.
Next job are the fascias and roof trim boards.

If anyone does read this and knows anything about solar lighting systems for the garage let me know. I'm thinking of a solar powered system to trickle charge a 70Ah leisure battery but I'm not sure what lights to run off it. Being a work shop space I want some fairly bright lights but low power consumption so I can run them off the leisure battery. Any thoughts?

 

[Ian H]

I wore old clothing that I could get rid of.

More of you wife's old stuff from the garage??

It looks good so far, are you still on budget?

 

[BIGbadmarky]

More of you wife's old stuff from the garage??

You'd be amazed how difficult it is doing DIY in a basque!

The budget has gone a bit out of the window. I'm probably about £200 - £300 over at the minute due mainly to underestimating things i.e delivery charges and other sundries. So far the spend has been about £1700. Even with the overspend I don't think thats too bad. I've not factored in getting rid of the old asbestos roof sheets yet. I had originally intended to drive them round to the local tip but they'll only accept 6ft sheets not the 9ft ones I have.

 

[Ian H]

What if you measure them widthways instead of lengthways?

 

[BIGbadmarky]

Another weekend in the garage. This time I got three of the four sides covered in fascias and roof trims.
The white fascias went on fairly easily but were a bit ungainly given that they were in 5m lengths. Not easy to handle in a breeze. I had to modify the fascia boards slightly as I had miscalculated the depth of the L shaped return at the bottom of the board. Turns out I had to trim about 15mm off each of the lip to fit against the wall and still allow air to circulate behind (to ventilate the roof space).

The design of the roof allows a 19mm void behind the fascias which allows the roof to breathe through the vent holes drilled into the frame of the roof and through each noggin of the roof structure. The vent holes are covered in insect mesh on the outside and will be treated with preservative (once I get round to it) so any condensation doesn't rot the wood. Theoretically the roof should allow the movement of air in the top 50mm to reduce condensation etc so when I get around to insulating the bottom 100mm I won't get a build up of condensation etc. I'll see how it does for a while first before I call it a success.

The roof trims went on pretty easily. I just had to squish the foam between the trim and the roof to form a weather seal. Even I couldn't muck that up!!


Next I need to replace the door frame and windows on the garden side so I can finish the roof and call it a job well done. I'll have to look through the carpentry forum to see if there is any guidance on making windows and door frames.