Trapdoor in 2 layers of floorboards

[thejazzlord]

Hi there, new to the forum so be gentle!

I need to get access to the underfloor of a ground floor room in the centre of my victorian terrace in Randwick, Sydney. The floor has newish floorboards layed on top of what I suspect are the original floorboards. Currently the underfloor of this room is sealed (bad for damp).

I'll need access for piping / electrics / ventilation etc. so I thought I'd put in a trapdoor.

1. I'll need to cut out a square from the floorboards to make the trapdoor, any tips on how to do this? the new floorboards are very tightly laid. Should I use a jigsaw? circular saw? hand saw?

2. I assume when cutting I'll need to know where the joists are underneath, but I can't see the lower layer with tell-tale nails, any ideas?

I can see this is going to get messy, luckily the previous owner left a stack of unused upper layer boards, so I could just gor for it and fix it all up later, if I can figure out how they finished it!

Mark

[OBBob]

Hi there, these would be my ideas ... maybe some help?

- Try a good studd finder, they may go through two layers of boards to see the joists.
- If you have spare boards then you could drill a tiny hole to start with (about where you would like the centre) then if that doesn't hit a joist open it up a bit so you can get a jigsaw in there. Then start to cut outward in each direction until the hole is large enough or you come to joists.
- Interms of cutting it once you have determined wher the joists are ... you could mark the outline of the hole then use a circular saw (i'd set the depth shallow just in case you missed a joist) then you could go around the edge with a router to clean it up ... you could even rebate it to make a nice draft proof seal on the new trapdoor.
- If possible chose a location that is out of the way ... like in a wardrobe, under a bed or a rug?

[Bleedin Thumb]

Sorry Mark I can't help you with finding the joists... tapping, stud finder?? I would assume that the new nails also go into the joists. are the nail holes at 450 mm spacings ?
Once you know where your joists are mark out your trapdoor and set the blade of the circular saw so that it is about 1mm deeper than your floor boards. Place the front of the saws base plate on the floor so that when you cut your blade will be on the line and you will be cutting down into the line, like you are immitating a drop saw.
Have the saw switched on (blade turning) before the blade touches the line
WARNING there is a real danger of kick back so be well balanced, hold the saw tight and always be in control!
Once your guard is fully flat onto the floor boards you can start moving forward stopping just as the front of the blade hits the corner.
Lift your saw out turn it around and place it back in the cut, then cut in the other direction till you hit the other corner.
Repeat on the other three sides. Finish of the corners with a hand saw.
Hopefuly others can suggest ways to find the joist and check for electrical wires. I'm not sure what will read through 2 layers of boards. I wouldn't be doing this without a very good earth leakage safety switch - the good ones are expensive but essential.
The only other thing that I can suggest is to use a heavy board as a straight edge guide to run the saw along so that you get nice straight lines. and plan your trapdoor so that it goes from centre of joist to centre of joist so you have less sub framing to do to support the door,

[Ashore]

Mark years ago we needed access like you in a terrace in Sydney, we put one in the cupboard under the stairs, so the question is are there any built ins, walkins, cupboards on the ground floor you could access.


Rgds

[thejazzlord]

Thanks for replies so far, all very helpful, looks like I'll need a circular saw and quite a bit of patience (do they sell that at Bunnies?).

Ashore - not a bad idea, I could go in under the stairs, I'll have a think about it,

OBob / Bleeding Thumb - thanks for the detailed responses.

Please feel free to keep adding more ideas

[bpj1968]

Do any of the other rooms have the original floor exposed. If so you could work oout eth joist spacing from them and hopefully (fingers crossed) the other rooms are the same. But I would go in under teh stairs or wardrobe if that is an option.

[RufflyRustic]

.......and quite a bit of patience (do they sell that at Bunnies?).
.........

No, they don't sell it, but you may learn some waiting for........

cheers
Wendy
_____________
Disclaimer: This may only be true some of the time, for some of the stores, for some of the employees and for some of the people who shop there.

[thejazzlord]

In regard to my questions above, I can't actually see any nails at all in the top layer of boards, would it be possible that they glued on the new floorboards to the lower ones? or maybe just used really small tacks?

Regards

Mark

[Clinton1]

maybe a good purchase for this job would be a metal detector (for finding nails in recycled timber)?
Cabatec, Timbecon and Mik would have them as well as the other 'usual suspects), Soundman (on this site) as well.

Edit: had a quick look at timbecon and carbatec, no luck. Maybe send a PM to Soundman??

[julianx]

The top floor could be a floating floor (what do the unused board look like are they solid timber or some sort of manufactured board). Otherwise the top boards may be secret nailed ie nailed through the toung of the board, nails are then hidden by the susequent boards.

[Dusty]

If you can see any part of the original flooring, under carpet, or at a ducted heating vent and determin which way the boards run it will be safe to assume that the room your intending to work in will run the same way.

Once you have the board direction, obviously the joists will run in the opposite direction, so, once you have figured out the joist direction simply measure about 440mm off the skirting board, and that should be your first joist, and then measure at 450mm intervals across the room and that might see you with cutting marks above the joists. If the room is either 1800mm,2250mm, 2700mm, 3150mm, 3600mm and so on you should be right, as all those sizes are divisible by 450mm which is the standard joist spacing.

However, if your room is an odd size you will have to perform the same action, but this time starting from the opposite wall.
The reason, in the case of an odd sized room, I'm suggesting you make those measurements from both ends of the room is because we have no way of determining which wall the original builders started to lay the joists from.

Once you have a fair idea where the joists should lie I suggest the you drill some thin pilot holes in unobtrusive places, like where furniture usually hangs out, or a rug or mat lies to see if you hit the joists.
You will know if the drill bit either hits or misses the mark.

Once you have successfully located the joists the rest of the project should be just the normal, standard Aussie renovation nightmare.

Gotta love the building game.
Good luck.

Dusty.

[thejazzlord]

Dusty / Julianx, thanks for the advice - very sensible, I suspect I have enought to go on from now. I'll do some measuring, drilling and sawing and I suspect I'll get there somehow, minus a few fingers, pride and various expletives. Still baffled as to why someone would completly seal a room in an area known for damp, maybe I'll find a few bodies down there.

The upper layer of boards are some sort of manufactured board, not solid, I suspect they use some sort of hidden nails in the tongue to locate them on the layer of boards below - hence they have no relationship to the joists at all. The boards actually compress and you can here a sort of 'crushing' noise when you apply pressure around a small area (like through your heel), so I suspect they were quite cheap.

One day, the whole lot is coming up!

[Bleedin Thumb]

I suspect that noise you hear may be rotten floorboards underneath.
You dont go and put a floating floor over perfectly good floor boards unless they are cactus.
With the movement and noise you have...hmmm.
The way to improve your damp problems is not by venting through your floor. If its an internal room you may have a leaky pipe under (or a spring) if its an external room its your external wall probably that needs damp proof coursing and or vents added.
Find whats causing the problem because you are wasting your time doing reno's if they are going to rot on you.
You want the area under the floor to be as dry as a pommies towel.