More on the loft door - plywood or blockboard?

[David.WE.Roberts]

Looking again at the current loft door it is 18mm plywood of some sort - although I am wondering if it is ply or some kind of blockboard.

Faced on both sides but the core looks quite solid.

Yes - just been back up and checked and it looks to be a core of quite wide mahogany blocks faced on either side by single ply mahogany sheet.

This is beginning to sound expensive.

However what started me back down this track is that the door feels quite light so doubling the size should still be supportable by hinges at one end and the original clips should hold it.

Now I've started looking at blockboard I can see Travis Perkins list two types: BLOCKBOARD BB/CC 5-PLY 18X2440X1220MM (441000) BLOCKBOARD FAR EAST CUT 1220X1220X18MM (948961) One is a full sheet (5 ply) and the other a half sheet (far east cut) but both are a similar price.

The Wiki is not very detailed about blockboard.

So should I go (depending on inspection) for the more expensive half sheet (which will be big enough) or is there another board such as ply which would do as well. [Looking back at the last thread the advice tended towards blockboard.] If so, which grade of ply?

The main requirements are to be able to screw into the end of the sheet to hold the whole thing up by a couple of hinges. Also to be able to paint the door easily.

Loft opening dimensions roughly 1200mm * 630mm.

I am really not very keen on 25mm MDF with socking great hinges.

I am going off the idea of a Celotex door in a frame as the plan it to insulate the loft at rafter level to make it warm (cool?) so I am not that bothered about a bit of heat leaking around the door.

Cheers

Dave R

[Bob Minchin]

Whenever I've used blockboard there seem to be voids just where I don't want them. Currently I have 12mm ply reinforced with 2x1 on the inside edge for hinges and the catch however mine are a more modest 550 x

800mm. They have been there since 1985 and not bowed but neither have I insulated them. Insulation is on the round-2-it list when I will possibly make a proper frame and panel type door.

[harry]

That will heavy to open and close. You need a "box" with a timber periphery and the thin ply sheet infill. Fill the box with rigid foam insulation, stuck in with canned foam and it will be light, rigid and reduced heat loss. Be sure to fit draught seal round the edges.

If you want an attached folding/extending loft ladder, it will need to open downwards not upwards. You can buy special catches for this.