Haunted House Time

In the next session I want to send my party to a haunted house. This is a really good opportunity to put into practice my resolution of piling on more atmospheric description (see last weeks post)

What I was hoping is that I could ask the readers here for more tips and your experiences of running a haunted house session. I am planning on the final showdown to be a zombies attacking from the grounds, breaking in through the doors, windows etc and slowly forcing the party up the stairs to the top of the house.

The lure to get them to the house will be to a meeting where they can learn something really important about one of the characters estrnged family.

Between the party arriving and the grand finale I want a skills based challenge for the party.So far I am thinking of having the house is a very poor state of repair so I can collapse the floor under someone (using moving maneuver skills), locked draws in a desk (subterfuge skills), Some kind of vault in the cellar (some kind of Lore based challenge maybe with runes that need interpretation).

I want to use the weather a lot with the wind ripping shutters open and banging them around, blowing curtains around etc. and flashes of lightning lighting up the scene in monochrome (probably revealing a zombie arching right over one of the party before the attack starts!)

Do you have any good advice? Is there anything you think I should avoid?

The party are all 3rd level but I feel they are punching above their weight (some good spell aquisition rolls have given them a rich set of spell lists along with the fact that ever character is a semi, hybrid or pure spell caster).