sole plate and fixing

Hi, some questions please on fixing a timber sole plate on to 100mm thick concrete block on top of dpc/dpm; ground floor (Timber frame wall panels will go on top of sole plate and bottom rail of the wall panels are 89x38mm cls timber)

Recommendations please for common sizes of sole plate for this? - I have heard/read various to use 25x100mm or 22x100 or 22x88mm.

I have read fix at 600mm centres using masonry nail, I have also read you can use expanding bolts. Can you advise on use of bolts and any good make of same as if they are stronger and get good recommendation then would prefer to use same if it gives me a stronger base. I have read I would need to seal the bigger hole this type of fixing makes in dpc and my next question would be how you do that?

What do you use to preserve soleplate – do you buy treated/tanalised timber or are there special preservatives you self treat timber with.

Thanks in advance !

Masonry nail every 500/600 will do. Or a bracket or strap.

The fixings don't have to be high strength, the panels are not going anywhere, but just need to stop any slight sideways movement.

If you use a bituminous felt, then the DPC will self seal. TRADA and BRE info indicates no problems with nailing through.

BS standards recommend treated timber where fungal attack risk is present. or where remedial work is difficult. You may as well use some treated timber though, for what its worth

Just make sure the wall below is reasonably level and straight and the joints full and blocks/bricks well bonded

Also consider the breather membrane termination, and installation of any DPC tray at the bottom of the panels, as you don't want any cavity moisture wicking back to the frame

just for piece of mind i have always chem fixed every 600ish and then sealed back around DPM with a blob of bitu. As Woody says once built and tied into floors etc it isn't going anywhere, but always feels a bit better to me than spikeing a few nails in.

thanks for comments woody & chappers. I will probably use masonry nails for sole plate (plus hold down straps to timber frame). Curious on this chem-fixing - i typed chem fix into google and went to fastfixdirect which has hammer and spin- in capsules - is that what chem fixing is - and how do you use them?

chem fix capsules are just one type, they come in a glass capsule and when you break it by hammering in the threaded bar the chemicals mix and form a two part adhesive. Other types come in tubes and are injected into the hole

Chem fixings are for situations requiring high pull out strength or for fixing in poor substrates where strength is required.

I would not waste time or expense with them for this situation

Hold down straps are only required for very exposed areas - like the Welsh coast and not say, the edge of Coventry