D.I.Y. manhole installation

Nailbag

A friend's house had an extension to his house that had a roofline that prevented internal roof access from the old to the new. So, he asked me to install a manhole that would allow some additional roof storage space.

These are usually a straight forward easy project, but I thought I would share this one as there were a few small challenges that are commonly found.

Materials

Builders Edge 600mm Manhole Frame

90mm x 45mm Framing Pine

75mm 8G batten screws

25mm Button head screws

Plasterboard screws

Stud glue

White Lined 3mm MDF panel

Tools

Tape measure

Pencil

Level / straight edge

Stud finder

Plasterboard hand saw

Mitre saw

Drill

Impact driver

Multitool

Multitool metal blade

Cordless light

Steps

Step 1

The first challenge is to find a suitable location for the manhole. It needed to be large enough to fit the cutout size clear of timbers, plumbing and electrical. But also allow a person to actually climb up and inside the roof space. 

The extension had a new low profile colourbond roof which wasn't practical to lift a sheet to help with our manhole location. So a lot of back and forth measurements were made. 

Eventually it was decided to install it in the new WIR.

Step 2

The new roof used trusses so, this meant the ceiling plasterboard was going to be fixed to steel battens which I needed to locate as well as clear any electrical cables when marking out the hole.

I used a stud finder to help find and mark a suitable central position. I then turned the lighting power off just as a safeguard before making a very shallow cut with a handsaw to make a trap-door style opening. This allowed me to get my arm up and feel around to double check I was 100% safe to make the full manhole cut out.

Plan B was to push the trapdoor back up and repair it back into position should the location not be suitable. But there wasn't going to be a Plan C so this needed to work which it did.

Step 3

Next I took measurements from each wall to mark out the manhole square to the ceiling. And then cut the manhole out in two manageable sections over letting one larger one fall to the ground.

Step 4

The position of the hole ended up being perfect other than this one ceiling batten which, I cut flush with my multitool and metal cutting blade.

With the opening complete I checked the manhole for fitment.

Step 5

As there were no timbers surrounding the internal opening to fix the plastic manhole frame, I needed to make my own frame up. This also had to have longer sections to reach to existing timber to secure mine to. 

The challenge here was to make a notch in my frame to clear a large tightly run of several electrical cables I couldn't move. But then still be able to safely fasten my frame.

Step 6

I had to assemble the frame inside the roof as it wouldn't fit through the cutout. I applied a few daps of stud glue under the fame before fixing it into place.

Pilot holes were drilled and batten screws used to both assemble and fasten the frame with plasterboard screws to fix the ceiling to the frame around the cutout.

 

Step 7

The manhole was installed using flat button head screws over countersunk to prevent any chance the pre-made holes in the frame didn't crush or split.

Step 8

I marked out and made the cover from a thin 3mm sheet of white lined MDF. usually I would make this out of 16mm melamine, but my friend was concerned about the weight and potential danger should it fall through should he not reposition it correctly.

Alternatively if you're able to cut the manhole out cleanly in one piece you can also use the plasterboard cutout for the cover lid. Some brands of manhole kits now come with covers.

A tip to reduce splintering during the cut, is to put the material face down as saw blades cut from the underside up. And adjust the height of the saw blade so it only protrudes about 5mm past the thickness of the material.

Step 9

And of course the last job is to fit the new manhole cover to complete the project.

MitchellMc

What a fantastic contribution, @Nailbag! This is a clear and well-presented project, and the end result looks excellent. The fit and finish of the manhole are really impressive, and it’s great to see such a practical solution executed so neatly. 

A job very well done!

Mitchell